Recovery Strategy for the Oregon Spotted Rana pretiosa Oregon Spotted Frog

Recovery Strategy for the Oregon Spotted Rana pretiosa Oregon Spotted Frog
Species at Risk Act
Recovery Strategy Series
Adopted under Section 44 of SARA
Recovery Strategy for the Oregon Spotted
Frog (Rana pretiosa) in Canada
Oregon Spotted Frog
2015
Recommended citation:
Environment Canada. 2015. Recovery Strategy for the Oregon Spotted Frog (Rana
pretiosa) in Canada. Species at Risk Act Recovery Strategy Series. Environment Canada,
Ottawa. 23 pp. + Annex.
For copies of the recovery strategy, or for additional information on species at risk,
including COSEWIC Status Reports, residence descriptions, action plans, and other
related recovery documents, please visit the Species at Risk (SAR) Public Registry1.
Cover illustration: © Kelly McAllister
Également disponible en français sous le titre
« Programme de rétablissement de la grenouille maculée de l’Oregon (Rana pretiosa) au
Canada »
© Her Majesty the Queen in Right of Canada, represented by the Minister of the
Environment, 2015. All rights reserved.
ISBN 978-0-660-03353-2
Catalogue no. En3-4/201-2015E-PDF
Content (excluding the illustrations) may be used without permission, with appropriate
credit to the source.
1
http://www.registrelep-sararegistry.gc.ca
RECOVERY STRATEGY FOR THE OREGON SPOTTED
FROG (Rana pretiosa) IN CANADA
2015
Under the Accord for the Protection of Species at Risk (1996), the federal, provincial,
and territorial governments agreed to work together on legislation, programs, and policies
to protect wildlife species at risk throughout Canada.
In the spirit of cooperation of the Accord, the Government of British Columbia has given
permission to the Government of Canada to adopt the "Recovery Strategy for the Oregon
Spotted Frog (Rana pretiosa) in British Columbia" (Part 2) under Section 44 of the
Species at Risk Act (SARA). Environment Canada has included an addition (Part 1)
which completes the SARA requirements for this recovery strategy.
The federal recovery strategy for the Oregon Spotted Frog in Canada consists of
two parts:
Part 1 – Federal Addition to the "Recovery Strategy for the Oregon Spotted Frog
(Rana pretiosa) in British Columbia", prepared by Environment Canada.
Part 2 - Recovery Strategy for the Oregon Spotted Frog (Rana pretiosa) in British
Columbia, prepared by the Canadian Oregon Spotted Frog Recovery Team for the
British Columbia Ministry of Environment.
TABLE OF CONTENTS
PART 1 - Federal Addition to the “Recovery Strategy for the Oregon Spotted
Frog (Rana pretiosa) in British Columbia”, prepared by Environment Canada ............... 1
PREFACE ....................................................................................................................... 2
1.
Species Status Information ................................................................................ 4
2.
Population and Distribution Objectives ............................................................... 4
3.
Critical Habitat .................................................................................................... 6
3.1 Identification of the Species’ Critical Habitat .................................................. 6
3.2 Schedule of Studies to Identify Additional Critical Habitat ............................ 10
3.3 Examples of Activities Likely to Result in Destruction of Critical Habitat ...... 11
4.
Statement on Action Plans ............................................................................... 14
5.
Effects on the Environment and Other Species................................................ 14
6.
References ....................................................................................................... 16
Appendix 1. Maps of critical habitat for Oregon Spotted Frog in Canada ..................... 19
PART 2 - Recovery Strategy for the Oregon Spotted Frog (Rana pretiosa) in
British Columbia, prepared by the Canadian Oregon Spotted Frog Recovery
Team for the British Columbia Ministry of Environment
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
PART 1 - Federal Addition to the “Recovery Strategy for
the Oregon Spotted Frog (Rana pretiosa) in British
Columbia”, prepared by Environment Canada
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Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
PREFACE
The federal, provincial, and territorial government signatories under the Accord for the
Protection of Species at Risk (1996) 2 agreed to establish complementary legislation and
programs that provide for effective protection of species at risk throughout Canada.
Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers
are responsible for the preparation of recovery strategies for listed Extirpated,
Endangered, and Threatened species and are required to report on progress within
five years.
The Minister of the Environment is the competent minister for the recovery of the Oregon
Spotted Frog and has prepared the federal component of this recovery strategy (Part 1), as
per section 37 of SARA. It has been prepared in cooperation with the Canadian Oregon
Spotted Frog Recovery Team and the Province of British Columbia. SARA section 44
allows the Minister to adopt all or part of an existing plan for the species if it meets the
requirements under SARA for content (sub-sections 41(1) or (2)). The Province of
British Columbia led the development of the attached recovery strategy for the Oregon
Spotted Frog (Part 2) in cooperation with Environment Canada.
Success in the recovery of this species depends on the commitment and cooperation of
many different constituencies that will be involved in implementing the directions set out
in this strategy and will not be achieved by Environment Canada, or any other
jurisdiction alone. All Canadians are invited to join in supporting and implementing this
strategy for the benefit of the Oregon Spotted Frog and Canadian society as a whole.
This recovery strategy will be followed by one or more action plans that will provide
information on recovery measures to be taken by Environment Canada and other
jurisdictions and/or organizations involved in the conservation of the species.
Implementation of this strategy is subject to appropriations, priorities, and budgetary
constraints of the participating jurisdictions and organizations.
The recovery strategy sets the strategic direction to arrest or reverse the decline of the
species, including identification of critical habitat to the extent possible. It provides all
Canadians with information to help take action on species conservation. When the
recovery strategy identifies critical habitat, there may be future regulatory implications,
depending on where the critical habitat is identified. SARA requires that critical habitat
identified within federal protected areas be described in the Canada Gazette, after which
prohibitions against its destruction will apply. For critical habitat located on federal lands
outside of federal protected areas, the Minister of the Environment must either make a
statement on existing legal protection or make an order so that the prohibition against
destruction of critical habitat applies. For critical habitat located on non-federal lands, if
the Minister of the Environment forms the opinion that any portion of critical habitat is
not protected by provisions in or measures under SARA or other Acts of Parliament, and
2
http://registrelep-sararegistry.gc.ca/default.asp?lang=en&n=6B319869-1#2
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Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
not effectively protected by the laws of the province or territory, SARA requires that the
Minister recommend that the Governor in Council make an order to extend the
prohibition against destruction of critical habitat to that portion. The discretion to protect
critical habitat on non-federal lands that is not otherwise protected rests with the
Governor in Council.
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Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
ADDITIONS AND MODIFICATIONS TO THE ADOPTED
DOCUMENT
The following sections have been included to address specific requirements of SARA that
are either not addressed, or which need more detailed information, in the Recovery
Strategy for the Oregon Spotted Frog (Rana pretiosa) in British Columbia (Part 2 of this
document, referred to henceforth as “the provincial recovery strategy”). In some cases,
these sections may also include updated information or modifications to the provincial
recovery strategy for adoption by Environment Canada.
1. Species Status Information
Legal Status: Endangered under Schedule 1 of SARA (2003).
Table 1. Conservation status of the Oregon Spotted Frog (from NatureServe 2011
and B.C. Conservation Framework 2010).
Global
(G)
Rank*
National
(N)
Rank*
Sub-national (S)
Rank*
COSEWIC
Status
B.C.
List
B.C.
Conservation
Framework
G2 (2011)
N1 (2011)
British Columbia (S1),
Washington (S1), Oregon
(S2), California (S1)
Endangered
(2011)
Red
Highest priority**:
1, under Goals***
1 and 3
*Rank 1 - Critically Imperiled; 2 - Imperiled; 3 - Vulnerable; 4 - Apparently Secure; 5 - Secure; H – possibly extirpated;
SNR – Status Not Ranked; SNA – Not Applicable
** Six level priority scale ranging from 1 (highest priority) to 6 (lowest priority)
*** The three goals of the B.C. Conservation Framework are: 1. Contribute to global efforts for species and ecosystem
conservation; 2. Prevent species and ecosystems from becoming at risk; 3. Maintain the diversity of native species and
ecosystems
It is estimated that the Canadian range of this species comprises less than 5% of its global
range (COSEWIC 2011).
2. Population and Distribution Objectives
Environment Canada supports the provincial Population and Distribution Goal and adopts
it as the Population and Distribution Objective for the Oregon Spotted Frog. The
Population and Distribution Goal and Rationale, outlined in sections 5.1 and 5.2 of the
provincial document, and provided here for reference, are as follows:
"5.1 Population and Distribution Goal
The population and distribution goal (within 10 years) is
To restore, maintain and where feasible expand extant Oregon Spotted Frog
populations, and establish six or more additional self-sustaining populations in BC.
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Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
5.2 Rationale for the Population and Distribution Goal
There are only four Oregon Spotted Frog populations known in B.C. with less than
350 individuals. One of the populations (Maintenance Detachment Aldergrove) is
possibly on the brink of extirpation. An additional four populations are known to be
extirpated. Each of the extant populations is isolated from the other populations, and
the probability of gene flow between populations, or recolonization is extremely low.
Suitable habitat within the range of the Oregon Spotted Frog has been lost and
degraded over time, largely as a result of land modification for agricultural or urban
development. Unless additional populations are created through re/introduction to
new and/or restored sites, the probability of species extirpation from B.C. is
considered high. The immediate goal is to prevent extirpation.
Habitat use pressures within the Oregon Spotted Frog range and the presence of
introduced species constrains the number of available new or reintroduction sites.
Although 13 potential sites are presented in Table 4 3, further investigation will likely
reveal that several of these sites are not suitable (e.g., may be too degraded to be
effective for recovery). With this in mind, the goal was set to establish 6 or more
populations over the next 10 years. This would result in the number of occupied
locations increasing from 4 to a minimum of 10 locations. A minimum number of
breeding adults at each location is needed to sustain viable populations. Until more
specific information is available, the population objective is 200 breeding adults per
location. It is recognized however, that the carrying capacity may limit what is
achievable and as a result targets will vary by location. In addition, it should be noted
that the distribution objective may slightly expand the species' range beyond the
historic sites, due to introductions into suitable habitat in the Fraser Valley that is not
known to have been occupied in the past.
In the time it takes to establish new or reintroduced populations, existing individual
populations must remain stable or increase. This will hopefully be achieved through
threat mitigation and population augmentation. If successful, extirpation of the
Oregon Spotted Frog will be prevented. It may be possible for the COSEWIC
designation to be upgraded from Endangered to Threatened, but further improvement
in conservation status is not expected given the limited amount and fragmented
nature of suitable habitat remaining for this species."
3
This table is found in the provincial recovery strategy, in part 2 of this document.
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Recovery Strategy for the Oregon Spotted Frog
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2015
3. Critical Habitat
This section provides information that augments, replaces, or references “Information on
habitat needed to meet recovery goal” (Section 7) in the provincial recovery strategy, as
identified in each subsection.
Section 41(1)(c) of SARA requires that recovery strategies include an identification of the
species’ critical habitat, to the extent possible, as well as examples of activities that are
likely to result in its destruction.
3.1 Identification of the Species’ Critical Habitat
This section replaces “Description of Survival/Recovery Habitat” (Section 7.1) in the
provincial recovery strategy.
Critical habitat for the Oregon Spotted Frog is identified in this recovery strategy to the
extent possible, based on the best available information. It is recognized that the critical
habitat identified below is insufficient to achieve the population and distribution
objectives for the species because it does not include habitat for the six or more additional
populations that must be established to meet the population and distribution objectives.
Critical habitat was not identified at historical or candidate introduction locations because
the habitat is currently unsuitable for the frog and/or the Canadian Oregon Spotted Frog
Recovery Team (the “recovery team”) has not confirmed which sites are suitable for
(re)introduction. Additional work is required prior to finalizing the list of introduction
locations (P. Govindarajulu pers. comm. 2011, M. M. Pearson pers. comm. 2011, K.
Welstead pers. comm. 2011). A schedule of studies (Section 3.2) has been developed to
provide the information necessary to complete the identification of critical habitat that will be
sufficient to meet the population and distribution objectives. The identification of critical
habitat will be updated when the information becomes available, either in a revised recovery
strategy or action plan(s).
The recovery team has developed a definition of habitat critical to the survival of Oregon
Spotted Frog (“survival habitat”) by identifying important biophysical attributes of
survival and recovery habitat and by identifying a process to geospatially describe the
necessary survival and recovery habitat. The process and areas of survival habitat
identified by the recovery team are outlined in “Procedure to describe survival and
recovery habitat” (Section 7.1.3) in the provincial recovery strategy. The criteria for
including habitat as critical habitat are outlined below, and capture the five process points
outlined in the provincial Description of Survival/Recovery Habitat, while providing
greater certainty about the location of Critical Habitat. The critical habitat identification
also excludes one element of the provincial survival habitat identification: the critical
habitat identification does not include an increase in width when impermeable surfaces
are present within the critical habitat area. The intent of creating this area was to
maintain hydrology and water quality. However, as it would be extremely difficult to
determine exactly where this additional critical habitat area is located, this element of the
survival/recovery habitat description was not included.
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Recovery Strategy for the Oregon Spotted Frog
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Critical habitat for Oregon Spotted Frog includes all habitats that meet any of the
following criteria:
1. All occupied habitat;
Criterion: the areas of the wetland and/or watercourses where any life stage (egg,
juveniles, adults, larvae/tadpoles) of Oregon Spotted Frog occurs or has been
known to occur.
2. All other suitable habitat in the watershed where it is feasible for the Oregon
Spotted Frog to colonize, and the connecting habitat;
Criteria:
a) all habitat within the same watershed that is suitable for Oregon Spotted Frog
(e.g., meets the biophysical attributes required by the species (Section 3.1.1);
or is identified as suitable using techniques such as habitat suitability
mapping), where:
• the habitat has an aquatic connection (perennial, ephemeral or
intermittent; e.g. water bodies, wetlands, ponds, ephemeral pools,
seeps, streams, areas of seasonal flooding, and ditches) to occupied
habitat (criterion 1); and
• the habitat is within 3 km (straight-line distance) of occurrence
records, and < 260 m in elevation
b) all other aquatic habitat (perennial, ephemeral or intermittent; e.g. water
bodies, wetlands, ponds, ephemeral pools, seeps, streams, areas of seasonal
flooding, and ditches, except for the Fraser River main stem) connected to
occupied habitat (criterion 1) where:
• the habitat is within 3 km (straight-line distance) of occurrence
records, and < 260 m in elevation
c) isolated patches (those without an aquatic connection) of a habitat type that is
suitable for Oregon Spotted Frog (e.g., meets the biophysical attributes
required by the species (Section 3.1.1); or is identified as suitable using
techniques such as habitat suitability mapping) where:
• the habitat is within 400 m (straight-line distance) of aquatic habitat
(criterion 2b) or other occupied or suitable habitat (criteria 1 or 2a);
and
• the habitat is within 3 km (straight-line distance) of occurrence
records, and is < 260 m in elevation.
3. All other areas that are required to maintain the attributes of the Oregon Spotted
Frog’s habitat (i.e., the quality and quantity of water).
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Recovery Strategy for the Oregon Spotted Frog
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2015
Criteria:
a) All types of groundwater flow (e.g. watercourses, intermittent streams,
springs or seeps, discharge areas, up-wellings), identified to their
headwaters, that influence the water quantity or quality of:
• the occupied habitats (criterion 1), or
• other suitable habitats in the watershed where it is feasible for the
Oregon Spotted Frog to colonize (criterion 2).
The areas of groundwater flow identified up to their headwaters may extend
> 3 km (straight-line distance) from occurrence records and > 260 m in
elevation
b) A 45 m wide area of critical habitat, measured from the high water mark 4,
immediately adjacent to habitats identified by criterion 1 and criterion 2.
Areas of impermeable surfaces (e.g. roads, parking lots, buildings) within the
45 m wide area are not considered critical habitat.
c) An area of critical habitat, measured from the high water mark, immediately
adjacent to all types of groundwater flow identified by criterion 3a. The width
of the areas depends on the surrounding dominant vegetation and land use:
• If the surrounding dominant land use is and will remain forestry, the
strip of area is 30 m wide on each side of the groundwater flow.
• If the surrounding dominant land use is agricultural or urban (not
forestry), or in harvested forest areas, the strip of area is 45 m wide on
each side of the groundwater flow.
For rationales and references to support these criteria, see “Procedure to describe survival
and recovery habitat” (Section 7.1.3) in the provincial recovery strategy. In addition to
the information in the provincial recovery strategy about riparian areas removing
chemicals such as herbicides, it should be noted that riparian areas can reduce the amount
of sediment that reach the waterway, which can help maintain the abundance and species
richness of amphibian communities (Vesely and McComb 2002, Rashin et al. 2006,
Crawford and Semlitsch 2007, Peterman and Semlitsch 2008). Peterman and Semlitsch
(2008) recommended retaining a 30 m forested zone around streams to reduce the input
of sediment into the waterway. Other studies on amphibian populations also recommend
the retention of a 30 m zone to preserve the characteristics of the resident amphibian
community (e.g., Crawford and Semlitsch 2007).
Critical habitat is identified around four known occupied locations of Oregon Spotted
Frog in the lower mainland of British Columbia: Aldergrove, Mountain Slough, Maria
Slough, and Morris Valley. The areas containing critical habitat for the Oregon Spotted
Frog are presented in Appendix 1, Figures A1 to A5. The shaded yellow polygons depict
areas where the criteria described in this section are met, and represent critical habitat,
except where areas of impermeable surfaces occur. The 10 km x 10 km UTM grid
4
“high water mark” means the visible high water mark of a stream where the presence and action of the
water are so common and usual, and so long continued in all ordinary years, as to mark on the soil of the
bed of the stream a character distinct from that of its banks, in vegetation, as well as in the nature of the soil
itself, and includes the active floodplain.
http://www.env.gov.bc.ca/habitat/fish_protection_act/riparian/documents/regulation.pdf accessed Oct 2011
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Recovery Strategy for the Oregon Spotted Frog
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2015
overlay shown on these figures is a standardized national grid system that highlights the
general geographic area containing critical habitat, for land use planning and/or
environmental assessment purposes.
3.1.1 Biophysical attributes of critical habitat
The Oregon Spotted Frog is a wetland/marsh specialist that prefers floodplain wetlands,
side channels, and sloughs associated with permanent waterbodies. These aquatic
habitats generally have good solar exposure with low to moderate amounts of cover by
emergent vegetation (25–50%; Watson et al. 2003), and silty, rather than gravelly
substrate. Nearby riparian vegetation moderates the microclimate, hydrology, and water
quality in the aquatic habitat. The structural attributes of native emergent and
submergent vegetation also influences habitat suitability (Pearl and Hayes 2004).
Habitat requirements are divided into three life-seasons: breeding (oviposition) and early
larval habitat, active summer habitat, and overwintering habitat. Dispersal/connective
habitat is required to link the three main habitat types during late spring and fall. Water
quality, maintained by limiting the introduction of fertilizers, pesticides, and sediments
into watercourses and wetlands, is a requirement in all habitat types.
Breeding and early larval habitat:
• areas that experience shallow inundation (<26 cm deep) in the spring (Pearl
and Hayes 2004);
• are >3° C in March/April (C. Bishop, unpubl. data, 2005, 2007); and
• contain indigenous aquatic vegetation (e.g., rushes, sedges, grasses,
pondweeds, buttercups) or moderate amounts of Reed Canarygrass (Phalaris
spp.).
Active Season (summer) habitat:
• wetlands that are >40 cm deep (R. Haycock, unpubl. data, 2001–2002, Watson
et al. 2003); and
• contain moderately dense, structurally diverse submergent, emergent, and
floating vegetation (Licht 1969, 1986a,b; McAllister and Leonard 1997,
Popescu 2012).
Over-winter habitat:
• springs, seeps, or low-flow channels that do not freeze in the winter and have
more stable levels of dissolved oxygen than other areas (Pearl and Hayes
2004); or
• in deeper water, beaver dams or areas of dense submerged vegetation (Hayes
et al. 2001, Watson et al. 2003, Chelgren et al. 2006, Govindarajulu 2008,
Pearson 2010, COSEWIC 2011).
Dispersal/connective habitat:
• any aquatic habitat not part of the Fraser River main stem, whether permanent
or ephemeral, that connects the three main habitat types during late spring and
fall.
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Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
3.2 Schedule of Studies to Identify Additional Critical Habitat
This section augments “Information on habitat needed to meet recovery goal” (Section 7)
in the provincial recovery strategy.
To meet the population and distribution objectives for Oregon Spotted Frog, studies are
required to identify additional critical habitat for the species. The following schedule of
studies (Table 2) outlines the activities required to identify additional critical habitat.
Table 2. Schedule of studies required to identify additional critical habitat for the Oregon
Spotted Frog.
Description of activity
Outcome/rationale
Timeline
Status
Identify locations suitable for
the identification of critical
habitat. Activities may include:
• Conducting surveys for
previously undiscovered
populations
• Identifying suitable
introduction locations
• Conducting threat
assessments at each site
• Identifying
rehabilitation/mitigation
measures necessary to make
the site suitable
•
Critical habitat for Oregon
Spotted Frog is based on
occurrence data. The
population and distribution
objectives for the species
require that at least six
additional populations of
Oregon Spotted Frog must
be discovered or
(re)established. To support
this objective, activities to
identify areas suitable for
the identification of critical
habitat must be conducted.
2015-2022
• Ongoing
Assess habitat and identify
critical habitat at six or more
additional locations as sites
become suitable through habitat
rehabilitation, threat mitigation,
or the introduction or discovery
of Oregon Spotted Frogs.
Activities will include:
• Identify habitat types at the
location using orthoimagery
and/or ground surveys and
assess them as to their
suitability for Oregon
Spotted Frog
• Identify all habitats at the
site that meet the criteria for
critical habitat
•
In order to support the
population and distribution
objective to restore,
maintain and where feasible
expand extant Oregon
Spotted Frog populations,
the habitat at each location
must be assessed and
critical habitat identified to
protect the occurrences.
2015-2022
• Habitat will be
assessed and
critical habitat
identified as
each site
becomes suitable
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Recovery Strategy for the Oregon Spotted Frog
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2015
3.3 Examples of Activities Likely to Result in Destruction of Critical
Habitat
This section replaces “Specific Human Activities Likely to Damage Survival/Recovery
Habitat” (section 7.2) in the provincial recovery strategy.
Understanding what constitutes destruction of critical habitat is necessary for the
protection and management of critical habitat. Destruction is determined on a case by
case basis. Destruction would result if part of the critical habitat were degraded, either
permanently or temporarily, such that it would not serve its function when needed by the
species. Destruction may result from a single or multiple activities at one point in time or
from the cumulative effects of one or more activities over time. Activities described in
Table 3 include those likely to cause destruction of critical habitat for the species;
destructive activities are not limited to those listed. Additional information on the
negative effects of these activities is provided in “Description of the Threats”
(Section 4.2) in the provincial recovery strategy.
Table 3. Examples of activities likely to result in destruction of critical habitat for Oregon
Spotted Frogs.
Activity
Hydrological
modifications
(e.g., ditching /
channelling, culverting,
ditch cleaning,
exposure of bedrock
through mining
operations, drawdown,
active removal of
beaver dams [but
excepting natural
beaver dam-building])
Release of pollutants
into watercourses or
wetlands
(e.g., runoff or spray of
pesticides or fertilizers,
runoff of manure stored
Description of how
activity would destroy
critical habitat
Hydrological modification
within or outside the area
of critical habitat can
result in water depths,
temperatures, and flow
rates that are outside the
range required for
successful breeding,
dispersal, and / or summer
and winter survival. The
timing of peak flows /
water depths and
temperatures is critical to
the function of the
different seasonal habitat
types, so destruction can
result when activities
modify these parameters
to a point where seasonal
requirements are not met.
Release of pollutants
within or outside the area
of critical habitat can
result in changes in water
chemistry leading to loss
of water quality required
for survival and successful
Relationship to
other activities
likely to result in
destruction?
Yes, changes in
water source
(from ground to
surface) can result
in greater inputs
of pollutants and
sediments into
watercourses and
wetlands.
No.
Timing
considerations
Applicable at all
times. Retaining
natural water levels
is important for
populations of
Oregon Spotted
Frog, particularly
during: the period
between
oviposition and
hatching of
tadpoles; overwinter during the
coldest period; and
in areas that are
required to support
oviposition, overwintering, foraging
or dispersal.
Applicable at all
times.
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Recovery Strategy for the Oregon Spotted Frog
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Activity
Description of how
activity would destroy
critical habitat
2015
Relationship to
other activities
likely to result in
destruction?
Timing
considerations
adjacent to habitat,
direct input of
manure/urine by cattle
or livestock, release of
leachate from mining
operations)
reproduction.
Inputs of sediment into
watercourses or
wetlands
Sedimentation within or
outside the area of critical
habitat can directly affect
water quality and modify
channel structure,
resulting in sediment
levels and water depths
outside the range required
for successful breeding
and/or summer and winter
survival.
Yes, the build-up
of sediment in the
watercourse /
wetland or the
watercourses that
input
water/materials to
the watercourse /
wetland can lead
to large runoff
events with a
resulting sudden
influx of
pollutants from
the surrounding
area.
Applicable at all
times.
Natural riparian
vegetation plays an
important role in
moderating microclimate
and hydrology. Removal
of natural riparian
vegetation within the area
of critical habitat can
result in water
temperatures, depths, and
flow rates/patterns that are
outside the range required
for successful breeding
and/or summer and winter
survival.
Yes, removal of
riparian
vegetation can
also reduce soil
stability, leading
to bank erosion
and increased
sedimentation.
Removal of
riparian
vegetation also
effects surface
permeability,
which increases
the rate at which
pollutants enter
wetlands /
watercourses.
Loss of natural
riparian
vegetation also
facilitates
invasion by exotic
plant species.
Applicable at all
times.
(e.g., forest harvest
within critical habitat
areas, allowing cattle
access to riparian areas,
mechanical or chemical
removal of riparian
vegetation)
Partial or total removal
of natural riparian
vegetation around
watercourses or
wetlands
(e.g., forest harvesting,
urban or agricultural
conversion, linear
developments, allowing
cattle access to riparian
areas)
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Recovery Strategy for the Oregon Spotted Frog
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Activity
Partial or total removal
of natural emergent or
submergent vegetation
(e.g., allowing cattle
access to riparian areas,
mechanical or chemical
removal of emergent /
submergent vegetation)
Introduction of semiaquatic exotic plant
species
(e.g., Reed Canarygrass
[Phalaris
arundinacea])
Installation of
impassable barriers
(e.g., impassable
culverts, dams, roads)
Description of how
activity would destroy
critical habitat
Removal of natural
emergent or submergent
vegetation within the area
of critical habitat can
result in densities below
the range required for
successful breeding and/or
summer and winter
survival.
2015
Relationship to
other activities
likely to result in
destruction?
No
Timing
considerations
Applicable at all
times.
Introduction of semiaquatic exotic plant
species, which grow in
greater densities than
native semi-aquatic plant
species, can result in
emergent and submergent
vegetation densities
outside the range required
for successful breeding
and/or summer and winter
survival. Introduction of
exotic plants within or
outside the area of critical
habitat could destroy
critical habitat.
No.
Applicable at all
times.
Installation of impassable
barriers within the area of
critical habitat leads to
elimination of access
between breeding,
summer, and winter
habitats, which results in
loss of habitat function
and reduced gene flow.
Yes, installation
of barriers can
affect not only
movement of
Oregon Spotted
Frogs, but also
hydrology,
resulting in water
depths,
temperatures, and
flow rates that are
outside the range
required for
successful
breeding,
dispersal, and / or
summer and
winter survival.
Applicable at all
times
13
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
4. Statement on Action Plans
One or more federal action plans will be posted on the Species at Risk Public Registry by
2020.
5. Effects on the Environment and Other Species
A strategic environmental assessment (SEA) is conducted on all SARA recovery
planning documents, in accordance with the Cabinet Directive on the Environmental
Assessment of Policy, Plan and Program Proposals 5. The purpose of a SEA is to
incorporate environmental considerations into the development of public policies, plans,
and program proposals to support environmentally sound decision-making and to
evaluate whether the outcomes of a recovery planning document could affect any
component of the environment or any of the Federal Sustainable Development
Strategy’s 6 goals and targets (FSDS).
Recovery planning is intended to benefit species at risk and biodiversity in general.
However, it is recognized that strategies may also inadvertently lead to environmental
effects beyond the intended benefits. The planning process based on national guidelines
directly incorporates consideration of all environmental effects, with a particular focus on
possible impacts upon non-target species or habitats. The results of the SEA are
incorporated directly into the strategy itself, but are also summarized below in this
statement.
The provincial recovery strategy notes that recovery actions for Oregon Spotted Frog are
unlikely to have any negative effects on non-target species or communities within its
range, and may benefit other species at risk. The Oregon Spotted Frog uses similar areas
to the Salish Sucker (Catostomus catostomus), the Western Painted Turtle (Pacific Coast
population)(Chrysemys picta), the Oregon Forestsnail (Allogona townsendiana), and the
Pacific Water Shrew (Sorex bendirii), which are listed as Endangered under SARA; the
Red-legged Frog (Rana aurora), Western Toad (Anaxyrus boreas), Vancouver Island
Beggarticks (Bidens amplissima), and Great Blue Heron fannini subspecies (Ardea
herodias fannini), which are listed as Special Concern under SARA; as well as the
American Bittern (Botaurus lentiginosus) and Green Heron (Butorides virescens), which
are considered provincially to be of Special Concern. The site-level details of these
species’ habitat requirements may differ.
Recovery actions for Oregon Spotted Frog may include habitat protection of the wetland
and surrounding watercourses and habitat that influence conditions in the wetlands,
removal of exotic invasive species such as reed canarygrass and American Bullfrogs
(Lithobates catesbeianus), habitat creation of wetland habitat, as well as other activities
5
6
http://www.ceaa.gc.ca/default.asp?lang=En&n=B3186435-1
http://www.ec.gc.ca/dd-sd/default.asp?lang=En&n=CD30F295-1
14
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
with the goal of enhancement or restoration of habitat condition and function. These
actions will likely have a positive impact on the native flora and fauna that live in or visit
the wetlands and associated habitats.
15
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
6. References
Canadian Oregon Spotted Frog Recovery Team. 2011. Recovery strategy for the Oregon
Spotted Frog (Rana pretiosa) in British Columbia. Prepared for the B.C. Ministry of
Environment, Victoria, BC. 68 pp.
Chelgren, N.D., C.A. Pearl, J. Bowerman, and M.J. Adams. 2006. Oregon Spotted Frog
(Rana pretiosa) movement and demography at Dilman Meadow: implications for future
monitoring. U.S. Geological Survey, Reston, VA.
COSEWIC. 2011. COSEWIC assessment and status report on the Oregon Spotted Frog
Rana pretiosa in Canada. Committee on the Status of Endangered Wildlife in Canada.
Ottawa. xi + 47 pp. (www.sararegistry.gc.ca/status/status_e.cfm).
Craig, V. 2008. Proposed partial survival habitat identification for Oregon Spotted Frog
(Rana pretiosa) – DRAFT. Report prepared by Vanessa Craig, Ph.D., R.P.Bio, EcoLogic
Research, for the Oregon Spotted Frog Recovery Team. 53 pp.
Crawford, J.A., and R.D. Semlitsch. 2007. Estimation of core terrestrial habitat for
stream-breeding salamanders and delineation of riparian buffers for protection of
biodiversity. Conservation Biology 21:152-158
Govindarajulu, P.P. 2008. Literature review of impacts of glyphosate herbicide on
amphibians: what risks can the silvicultural use of this herbicide pose for amphibians in
B.C.? B.C. Min. Environ., Victoria, BC. Wildlife Report No. R-28.
Hallock, L. and S. Pearson. 2001. Telemetry study of fall and winter Oregon Spotted
Frog (Rana pretiosa) movement and habitat use at Trout Lake, Klickitat County,
Washington. 36 pp. Cited in Pearl and Hayes (2004) and Cushman and Pearl (2007).
Hawkes, V. C. 2009. Salish Sucker (Catostomus sp.) and Oregon Spotted Frog (Rana
pretiosa) habitat investigations and effluent review at Maintenance Detachment
Aldergrove with a proposed survival habitat delineation for Oregon Spotted Frog.
Unpublished report by LGL Limited, LGL Project EA3132 for Public Works and
Government Services Canada, Victoria, BC. 67 pp + Appendices.
Hawkes, V.C. 2010. Oregon Spotted Frog (Rana pretiosa) survival and recovery habitat
mapping for extant and historical populations and a potential reintroduction site in
southwestern British Columbia. LGL Project EA3193. Unpublished report by
LGL Limited environmental research associates, Sidney, BC for the Fraser Valley
Conservancy, Abbostsford, BC. 94 pp.
16
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Hayes, M.P., J.D. Engler, S. Van Leuven, D.C. Friesz, T. Quinn, and D.J. Pierce. 2001.
Overwintering of the Oregon Spotted Frog (Rana pretiosa) at Conboy National Wildlife
Refuge, Klickitat County, Washington 2000–2001. Final report to the Washington
Department of Transportation. Washington Department of Fish and Wildlife, Olympia,
WA. 86 pp. Cited in Pearl and Hayes (2004).
Licht, L.E. 1969. Comparative breeding behavior of the red-legged frog (Rana aurora
aurora) and the western spotted frog (Rana pretiosa pretiosa) in southwestern British
Columbia. Canadian Journal of Zoology 47: 1287–1299.
Licht, L.E. 1986a. Comparative escape behavior of sympatric Rana aurora and Rana
pretiosa. The American Midland Naturalist 115:239–247.
Licht, L.E. 1986b. Food and feeding behavior of sympatric red-legged frogs, Rana
aurora, and spotted frogs, Rana pretiosa, in southwestern British Columbia. The
Canadian Field-Naturalist 100:22–31.
McAllister, K.R. and W.P. Leonard. 1997. Washington State status report for the Oregon
Spotted Frog. Washington Dep. Fish and Wildlife, Seattle, WA. 38 pp.
NatureServe. 2011. NatureServe Explorer: An online encyclopedia of life [web
application]. Version 7.1. NatureServe, Arlington, Virginia. Available
http://www.natureserve.org/explorer. (Accessed: November 7, 2011).
Pearl, C.A. and M.P. Hayes. 2004. Habitat associations of the Oregon Spotted Frog
(Rana pretiosa): a literature review. Final report. Washington Dep. Fish and Wildlife,
Olympia, WA.
Pearson, M. M. 2010. Oregon Spotted Frog habitat prioritization in preparation for OSF
introduction to new habitats. Unpublished report prepared for the Oregon Spotted Frog
Recovery Team, Fraser Valley Conservancy, B.C. Conservation Foundation, and South
Coast Conservation Program. 31 pp.
Peterman, W.E., and R.D. Semlitsch. 2008. Impacts of even-aged timber harvest on larval
salamanders and the efficacy of riparian buffers in mitigating population declines. Forest
Ecology & Management 257:8-14.
Popescu, V.D. 2012. Habitat selection by Oregon Spotted Frogs (Rana pretiosa) in
British Columbia. Unpublished report prepared for the Canadian Wildlife Service and
the Oregon Spotted Frog Recovery Team. 29 pp.
Rashin, E. B., C. J. Clishe, A. T. Loch, and J. M. Bell. 2006. Effectiveness of timber
harvest practices for controlling sediment related water quality impacts. Journal of the
American Water Resources Association 42 (5):1307-1327.
17
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Vesely, D.G. and W.C. McComb. 2002. Salamander abundance and amphibian species
richness in riparian buffer strips in the Oregon Coast Range. Forest Science 48:291–297.
Watson, J.W., K.R. McAllister, and D.J. Pierce. 2003. Home ranges, movements, and
habitat selection of Oregon Spotted Frogs (Rana pretiosa). J. Herpetol. 37:292–300.
Personal Communications
Govindarajulu, P. Amphibian Specialist and Oregon Spotted Frog Recovery Team
Co-Chair. B.C. Ministry of Environment, Victoria, B.C.
Hayes, M. Senior Research Scientist and Oregon Spotted Frog Expert. Washington
Department of Fish and Wildlife, Olympia, Washington, U.S.A.
Pearson, M. M. Environmental Consultant and Oregon Spotted Frog Expert. Balance
Ecological, Vancouver, B.C.
Welstead, K. Species at Risk Biologist and Oregon Spotted Frog Recovery Team
Co-Chair. B.C. Ministry of Forests, Lands, and Natural Resource Operations, Surrey,
B.C.
18
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
APPENDIX 1. MAPS OF CRITICAL HABITAT FOR OREGON SPOTTED FROG IN
CANADA
Figure A.1. The four areas within which critical habitat occurs for the Oregon Spotted Frog in Canada. Critical habitat is identified at the four extant
locations of Oregon Spotted Frog: Mountain Slough, Maria Slough, Morris Valley, and Aldergrove.
19
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Figure A.2. . Critical habitat for the Oregon Spotted Frog at Mountain Slough (Agassiz, B.C.) is represented by the
yellow shaded polygons comprising 940 ha, where the criteria and methodology set out in section 3.1 are met.
The 10 km x 10 km UTM grid overlay shown on this figure is a standardized national grid system that indicates the
general geographic area containing critical habitat.
20
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Figure A.3. Critical habitat for the Oregon Spotted Frog at Maria Slough (Agassiz, B.C.) is represented by the yellow
shaded polygons comprising 906.4 ha, where the criteria and methodology set out in section 3.1 are met. The 10 km x
10 km UTM grid overlay shown on this figure is a standardized national grid system that indicates the general
geographic area containing critical habitat.
21
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Figure A.4. Critical habitat for the Oregon Spotted Frog at Morris Valley (Fraser Valley Regional District, B.C.) is represented by the yellow shaded
polygons comprising 1250 ha, where the criteria and methodology set out in section 3.1 are met. The 10 km x 10 km UTM grid overlay shown on
this figure is a standardized national grid system that indicates the general geographic area containing critical habitat
22
Recovery Strategy for the Oregon Spotted Frog
PART 1: Federal Addition
2015
Figure A.5. Critical habitat for the Oregon Spotted Frog at Aldergrove (Township of Langley, B.C.) is represented by the yellow shaded polygons
comprising 620 ha, where the criteria and methodology set out in section 3.1 are met. The 10 km x 10 km UTM grid overlay shown on this figure is
a standardized national grid system that indicates the general geographic area containing critical habitat.
23
PART 2 - Recovery Strategy for the Oregon Spotted Frog
(Rana pretiosa) in British Columbia, prepared by the
Canadian Oregon Spotted Frog Recovery Team for the
B.C. Ministry of Environment
British Columbia Recovery Strategy Series
Recovery Strategy for the Oregon Spotted Frog
(Rana pretiosa) in British Columbia
Prepared by the Canadian Oregon Spotted Frog Recovery Team
January 2012
Updated - August 2014
About the British Columbia Recovery Strategy Series
This series presents the recovery strategies that are prepared as advice to the Province of British
Columbia on the general strategic approach required to recover species at risk. Recovery
strategies are prepared in accordance with the priorities and management actions assigned under
the British Columbia Conservation Framework. The Province prepares recovery strategies to
ensure coordinated conservation actions and meet its commitments to recover species at risk
under the Accord for the Protection of Species at Risk in Canada, and the Canada – British
Columbia Agreement on Species at Risk.
What is recovery?
Species at risk recovery is the process by which the decline of an endangered, threatened, or
extirpated species is arrested or reversed, and threats are removed or reduced to improve the
likelihood of a species’ persistence in the wild.
What is a recovery strategy?
A recovery strategy summarizes the best available science-based knowledge of a species or
ecosystem to identify goals, objectives, and strategic approaches that provide a coordinated
direction for recovery. These documents outline what is and what is not known about a species
or ecosystem, identify threats to the species or ecosystem, and what should be done to mitigate
those threats.
Recovery strategies are usually prepared by a recovery team with members from agencies
responsible for the management of the species or ecosystem, experts from other agencies,
universities, conservation groups, aboriginal groups, and stakeholder groups as appropriate.
For more information
To learn more about species at risk recovery in British Columbia, please visit the Ministry of
Environment Recovery Planning webpage at:
<http://www.env.gov.bc.ca/wld/recoveryplans/rcvry1.htm>
To learn more about the British Columbia Conservation Framework, please visit the Ministry of
Environment Conservation Framework webpage at:
< http://www.env.gov.bc.ca/conservationframework/>
Recovery Strategy for Oregon Spotted Frog
January 2012
Recovery Strategy for the Oregon Spotted Frog (Rana pretiosa) in
British Columbia
Prepared by the Canadian Oregon Spotted Frog Recovery Team
January 2012
Updated - August 2014
Recovery Strategy for Oregon Spotted Frog
January 2012
Recommended citation
Canadian Oregon Spotted Frog Recovery Team. 2014. Recovery strategy for the Oregon Spotted
Frog (Rana pretiosa) in British Columbia. Repr. of 1st ed., Prepared for the B.C. Ministry of
Environment, Victoria, BC. 59 pp. (Orig. pub. 2012)
Cover illustration/photograph
Cover photo by Purnima Govindarajulu – used with permission.
Additional copies
Additional copies can be downloaded from the B.C. Ministry of Environment Recovery Planning
webpage at:
<http://www.env.gov.bc.ca/wld/recoveryplans/rcvry1.htm>
Publication information
This is an updated version of the January 2012 first edition of this document.
See Updates for specific changes to the document.
Updates
Updated August 2014 - Changes to the original posting (January 2012) include correction of
captions to Figure A1 and Figure A2 which were reversed in original publication, as well as
correcting references to Tables in the document.
i
Recovery Strategy for Oregon Spotted Frog
January 2012
Disclaimer
This recovery strategy has been prepared by the Canadian Oregon Spotted Frog Recovery Team,
as advice to the responsible jurisdictions and organizations that may be involved in recovering
the species. The British Columbia Ministry of Environment has received this advice as part of
fulfilling its commitments under the Accord for the Protection of Species at Risk in Canada, and
the Canada – British Columbia Agreement on Species at Risk.
This document identifies the recovery strategies that are deemed necessary, based on the best
available scientific and traditional information, to recover Oregon Spotted Frog populations in
British Columbia. Recovery actions to achieve the goals and objectives identified herein are
subject to the priorities and budgetary constraints of participatory agencies and organizations.
These goals, objectives, and recovery approaches may be modified in the future to accommodate
new objectives and findings.
The responsible jurisdictions and all members of the recovery team have had an opportunity to
review this document. However, this document does not necessarily represent the official
positions of the agencies or the personal views of all individuals on the recovery team.
Success in the recovery of this species depends on the commitment and cooperation of many
different constituencies that may be involved in implementing the directions set out in this
strategy. The Ministry of Environment encourages all British Columbians to participate in the
recovery of Oregon Spotted Frogs.
ii
Recovery Strategy for Oregon Spotted Frog
January 2012
RECOVERY TEAM MEMBERS
Members:
Kym Welstead - Chair
B.C. Ministry of Forests, Lands and Natural Resource Operations, Surrey, BC
Christine Bishop
Environment Canada – Science and Technology Branch, Delta, BC
Gordon Blankstein
(Malcom Wheatherston)
Mountain View Conservation and Breeding Society, Langley, BC
Purnima Govindarajulu
BC Ministry of Environment, Victoria, BC
Jude Grass
Metro Vancouver Parks (retired), Community Stewardship Liaison, Vancouver, BC
Bob Johnson
(Andrew Lentini)
Toronto Zoo, Toronto, ON
Brian Jones
(Kenna McNeil)
Seabird Island Band, Agassiz, BC
Ken Macquisten
Grouse Mountain Refuge for Endangered Wildlife, North Vancouver, BC
Wendy Palen
(Amanda Kissel)
Simon Fraser University, Department of Biological Sciences, Burnaby, BC
Kristina Robbins
B.C. Ministry of Forests, Lands and Natural Resource Operations, Surrey, BC
Dan Shervill
Environment Canada – Canadian Wildlife Service, Delta, BC
Graham Smith
(Tracy Cornforth)
Department of National Defense, Canadian Forces Base Esquimalt, Victoria, BC
Christopher Steeger
(Cindy Hulst; Menita Prasad)
Greater Vancouver Zoological Centre, Aldergrove, BC
Dennis Thoney
Vancouver Aquarium, Vancouver, BC
Bob Woods
Department of National Defense (retired), Ottawa, ON
*Alternates identified in parentheses
Observers:
Matthew Connolly
District of Kent, Kent, BC
Vanessa Craig
Ecologic Research, Vancouver Island, BC
Marc Hayes
Washington Department of Fish and Wildlife, Olympia, WA
Denis Knopp
B.C.’s Wild Heritage, Chilliwack, BC
Patrick Mooney
University of British Columbia, Landscape Architecture, Vancouver, BC
Mike Pearson
Pearson Ecological, Agassiz, BC
Monica Pearson
Balance Ecological, Vancouver, BC
Carrielynn Victor
Stó:lō Tribal Council, Agassiz, BC
Lance Lilley
Watershed Planner, Fraser Valley Regional District, BC
iii
Recovery Strategy for Oregon Spotted Frog
January 2012
RESPONSIBLE JURISDICTIONS
The British Columbia Ministry of Environment is responsible for producing a recovery strategy
for Oregon Spotted Frog under the Accord for the Protection of Species at Risk in Canada.
Canadian Wildlife Service of Environment Canada participated in the preparation of this
recovery strategy.
ACKNOWLEDGEMENTS
The development of this document has been ongoing since 2003. Initial drafts of this document
were prepared by Vanessa Craig (EcoLogic Research) and Russ Haycock (Hyla Environmental
Services Ltd.). This version of the document is a result of the work of Kym Welstead, Kristina
Robbins (B.C. Ministry of Forests, Lands and Natural Resource Operations), and Purnima
Govindarajulu (B.C. Ministry of Environment) who extensively updated these drafts and
authored several new sections with input from the Canadian Oregon Spotted Frog Recovery
Team. Individuals identified in the Recovery Team Members section represent the configuration
of the recovery team as of March 2011. In addition to these individuals, many former members,
observer and alternates have contributed to this document and the recovery of this species.
Former members, observers and alternates of the recovery team include: David Fraser, Mark
Hayes, Mike Pearson, Monica Pearson, John Richardson, Denis Knopp, Sylvia Letay, Laura
Friis, Jamie Dorgan, Janice Jarvis, Russ Haycock, Stephanie Blouin, Danielle Smith, Arimathea
Pappas, Rick Hebner, June Harris, Dave Dunbar, Andrea Gielens, Rene McKibbin, Annette
Potvin and Kevin Bowen. Members of the recovery team and Russ Haycock, Denis Knopp,
Virgil Hawkes, and Monica Pearson shared unpublished data. The document was formatted to
conform to standard templates (Ministry of Environment 2010a) by Leah Westereng (B.C.
Ministry of Environment) and Paul Chytyk (YUNI Environmental Consulting). Other reviewers
include Leah Westereng, Dan Shervill (Environment Canada) and David Cunnington
(Environment Canada). The World Wildlife Fund Canada and the B.C. Ministry of Environment
funded the development of this Recovery Strategy.
.
iv
Recovery Strategy for Oregon Spotted Frog
January 2012
EXECUTIVE SUMMARY
The Oregon Spotted Frog (Rana pretiosa) is a Pacific Northwest endemic whose global
historical distribution ranged from the southwestern corner of British Columbia south to the
northeastern corner of California. It is Canada’s most endangered amphibian, with an estimated
population of only 316 adults at 4 occupied locations (one of which may be near extirpation) in
2010.
The Oregon Spotted Frog is endangered throughout its North American range. It is extirpated
from at least 70% of its known historical locations and as much as 90% of its extrapolated
historical range. There is an immediate need to facilitate its recovery to a level at which
extinction is no longer an immediate threat.
Based on the Oregon Spotted Frog’s limited distribution, small population sizes, and small
habitat areas, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) first
designated the Oregon Spotted Frog as “Endangered” in November 1999. The Oregon Spotted
Frog is listed as Endangered in Canada on Schedule 1 of the Species at Risk Act (SARA). In
British Columbia, the Oregon Spotted Frog is ranked S1 (critically imperiled) by the
Conservation Data Centre and is on the provincial Red list. The B.C. Conservation Framework
ranks the Oregon Spotted Frog as a priority 1 under Goal 1 (contribute to global efforts for
species and ecosystem conservation) and Goal 3 (maintain the diversity of native species and
ecosystems).
Habitat loss as a result of land developments, agricultural land conversion, resource extraction
and hydrological alternations has occurred historically and is likely the predominant cause of the
decline of the Oregon Spotted Frog throughout its North American range. With only four
remaining Canadian breeding populations (one of which may be near extirpation) and less than
350 estimated breeding individuals, the risk of demographic and environmental stochastic events
is high and could result in further local extirpations. Threats with a very high or high overall
impact on the Oregon Spotted Frog (as scored by the World Conservation Union-Conservation
Measures Partnership classification) include invasive and other problematic species and genes,
human intrusions and disturbance, and pollution. Threats with an overall impact scoring of
moderate include agriculture, energy production and mining, and natural system modifications.
These threat factors lead to the following stresses: habitat loss, habitat degradation, direct and
indirect mortality, and accidental mortality.
The population and distribution goal for the Oregon Spotted Frog is
To restore, maintain and where feasible expand extant Oregon Spotted Frog populations, and
establish six or more additional self-sustaining populations in BC.
In the time it takes to accomplish this goal, existing individual populations must remain stable or
increase over the next 10 years.
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Recovery Strategy for Oregon Spotted Frog
January 2012
The recovery objectives for the Oregon Spotted Frog are:
1. to prevent further habitat degradation/loss and population declines of Oregon Spotted Frog
by protecting 1, managing, and restoring habitat at all four occupied locations; at additional
occupied sites if found (see Objective 4), and at additional locations or sites established
through population introduction/reintroduction (see Objective 3)
2. to sustain or improve survivorship rates of all life stages of the Oregon Spotted Frog
where needed through threat mitigation, habitat restoration, and population augmentation;
3. to establish/re-establish self-sustaining populations at a minimum of six additional
historical, suitable, or restorable sites;
4. to prevent inadvertent loss of currently unidentified populations by conducting a
comprehensive inventory of potentially suitable habitat;
5. to determine the effectiveness of habitat protection/enhancement and population
augmentation/reintroduction measures by monitoring population status; and
6. to adaptively improve conservation and recovery efforts by addressing knowledge gaps in
the life-history, population ecology, threats, and habitat requirements of the species.
It is recommended that occupied habitat be protected using the current knowledge of the
biological and habitat needs of the species. Protection of occupied sites alone will likely not be
sufficient to prevent extirpation. Additional recovery habitat areas will also be needed to support
the recovery of this species. Given that the Oregon Spotted Frog habitat is predominantly
surrounded by private lands, stewardship efforts (involving the voluntary cooperation of
landowners) will be important to their conservation and recovery.
RECOVERY FEASIBILITY SUMMARY
The recovery of the Oregon Spotted Frog in B.C. is considered biologically and technically
feasible based on the criteria outlined by the Government of Canada (2009):
1. Individuals of the wildlife species that are capable of reproduction are available now or in
the foreseeable future to sustain the population or improve its abundance.
Yes, monitoring of the 4 known populations indicates that reproductive individuals are
present in at least 3 of the populations, and are capable of reproduction (the status of the
population at Maintenance Detachment Aldergrove is currently in question).
2. Sufficient suitable habitat is available to support the species or could be made available
through habitat management or restoration.
Yes, suitable habitat exists at currently occupied sites and additional suitable
reintroduction sites have been identified. A series of broad-scale habitat suitability criteria
have been developed and preliminary screening and monitoring of these habitats are
1
Protection can be achieved through various mechanisms including: voluntary stewardship agreements,
conservation covenants, sale by willing vendors on private lands, land use designations, and protected areas.
vi
Recovery Strategy for Oregon Spotted Frog
January 2012
underway. Jointly the existing and reintroduction sites will provide sufficient suitable
habitat.
3. The primary threats to the species or its habitat (including threats outside Canada) can be
avoided or mitigated.
Yes, identified threats can be at least partially mitigated through habitat protection,
management, restoration, and rehabilitation.
4. Recovery techniques exist to achieve the population and distribution objectives or can be
expected to be developed within a reasonable timeframe.
Yes, captive breeding, captive rearing, and release will be used both to augment
populations at known locations, and to establish populations at historic and new locations
created through habitat restoration and rehabilitation.
The Canadian Oregon Spotted Frog Recovery Team has determined that recovery is biologically
and technically feasible, providing that ongoing management intervention occurs. Intervention is
required to ensure that habitat is protected and restored, and that threats are alleviated.
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Recovery Strategy for Oregon Spotted Frog
January 2012
TABLE OF CONTENTS
RECOVERY TEAM MEMBERS ...................................................................................... iii
RESPONSIBLE JURISDICTIONS ..................................................................................iv
ACKNOWLEDGEMENTS ...............................................................................................iv
EXECUTIVE SUMMARY................................................................................................. v
RECOVERY FEASIBILITY SUMMARY...........................................................................vi
1
COSEWIC SPECIES ASSESSMENT INFORMATION ........................................... 1
2
SPECIES STATUS INFORMATION ....................................................................... 1
3
SPECIES INFORMATION ...................................................................................... 2
3.1 Species Description ............................................................................................ 2
3.2 Populations and Distribution ............................................................................... 3
3.3 Needs of the Oregon Spotted Frog..................................................................... 8
3.3.1 Habitat and biological needs .......................................................................... 8
3.3.2 Ecological role .............................................................................................. 12
3.3.3 Limiting factors ............................................................................................. 12
4
THREATS ............................................................................................................. 15
4.1 Threat Classification ......................................................................................... 16
4.2 Description of the Threats................................................................................. 18
4.2.1 Very high, high and medium impact threats ................................................. 18
4.2.2 Medium impact threats ................................................................................. 23
4.2.3 Low impact threats ....................................................................................... 25
5
RECOVERY GOAL AND OBJECTIVES ............................................................... 28
5.1 Population and Distribution Goal ...................................................................... 28
5.2 Rationale for the Population and Distribution Goal ........................................... 28
5.3 Recovery Objectives ......................................................................................... 29
6
APPROACHES TO MEET OBJECTIVES ............................................................. 29
6.1 Actions Already Completed or Underway ......................................................... 30
6.2 Knowledge Gaps .............................................................................................. 32
6.3 Recovery Planning Table.................................................................................. 34
6.4 Description of the Recovery Planning Table ..................................................... 37
6.4.1 List under Wildlife Act ................................................................................... 38
6.4.2 Habitat Protection, Land Stewardship and Restoration ................................ 38
6.4.3 Species and Population Management .......................................................... 38
6.4.4 Planning ....................................................................................................... 40
7
INFORMATION ON HABITAT NEEDED TO MEET RECOVERY GOAL.............. 41
7.1 Description of Survival/Recovery Habitat ......................................................... 41
7.1.1 Habitat needed for survival and recovery ..................................................... 41
7.1.2 Biophysical attributes of survival and recovery habitat ................................. 42
7.1.3 Procedure to describe survival and recovery habitat .................................... 42
7.2 Specific Human Activities Likely to Damage Survival/Recovery Habitat ........... 45
8
Performance Measures......................................................................................... 46
9
EFFECTS ON OTHER SPECIES ......................................................................... 48
10
REFERENCES ................................................................................................. 49
Appendix 1. Population estimates at occupied sites in British Columbia ....................... 53
Appendix 2. Site-specific threat assessment ................................................................. 55
Appendix 3. Maps of survival habitat for Oregon Spotted Frog in B.C. ......................... 56
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Recovery Strategy for Oregon Spotted Frog
January 2012
LIST OF TABLES
Table 1. Status and description of Oregon Spotted Frog populations in British Columbia.
........................................................................................................................................ 7
Table 2. Threat classification table for Oregon Spotted Frog. ....................................... 16
Table 3. Recovery planning table for Oregon Spotted Frog in British Columbia. .......... 34
Table 4. Potential introduction, reintroduction or population expansion sites for Oregon
Spotted Frog in B.C. Sites that have an * were used in the threat scoring. ................... 39
Table 5. Examples of human activities likely to damage survival/recovery habitat for
Oregon Spotted Frog..................................................................................................... 45
LIST OF FIGURES
Figure 1. Adult female Oregon Spotted Frog................................................................... 2
Figure 2. Present and historical distribution of the Oregon Spotted Frog in North
America. .......................................................................................................................... 4
Figure 3. Map illustrating location of four extant populations and four historical
populations of Oregon spotted frog.. ............................................................................... 6
Figure 4. Typical oviposition habitat for Oregon Spotted Frog at Mountain Slough......... 9
Figure 5. Oviposition site. The egg cluster in the foreground is coloured green by algae.
A groundwater-fed spring inputs warmer fresh water adjacent to the cluster. ............... 10
Figure 6. Map illustrating the floodplain area of the lower Fraser River (light blue area).
The floodplain overlaps with the historic and current extant range of the species. ........ 14
Figure 7. Drainage into Mountain Slough between two oviposition sites. ...................... 22
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Recovery Strategy for Oregon Spotted Frog
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1 COSEWIC SPECIES ASSESSMENT INFORMATION
In Canada, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has
assessed Oregon Spotted Frog (Rana pretiosa) as Endangered nationally (COSEWIC 2011).
Date of Assessment: May 2011
Common Name (population): Oregon Spotted Frog
Scientific Name: Rana pretiosa
COSEWIC Status: Endangered
Reason for designation: This highly aquatic frog has a small Canadian distribution within the
populated and highly modified Fraser River Basin in southwestern British Columbia. It currently
occurs at four sites, isolated from one another, and has been extirpated from an additional three sites.
One extant population is near extinction, and the remaining populations are small and vulnerable to
disturbance and stochastic events. Habitat loss and fragmentation, hydrological alteration, disease,
introduced predators, and poor water quality continue to threaten remnant populations.
Canadian Occurrence: British Columbia
COSEWIC Status History: Designated Endangered in an emergency assessment on 13 September
1999. Status re-examined and confirmed in May 2000 and in May 2011.
2 SPECIES STATUS INFORMATION
Oregon Spotted Frog
a
Legal Designation:
b
c
Identified Wildlife: No
Conservation Status
B.C. List: Red
B.C. Wildlife Act: Schedule A
SARA Schedule: 1 (2003)
d
B.C. Rank: S1 (2010)
National Rank: N1 (1998)
Global Rank: G2 (2010)
e
Subnational Ranks: S1 in WA and CA; S2 in OR
f
B.C. Conservation Framework (CF)
g
Goal 1: Contribute to global efforts for species and ecosystem conservation. Priority: 1 (2009)
Goal 2: Prevent species and ecosystems from becoming at risk.
Priority: 6 (2009)
Goal 3: Maintain the diversity of native species and ecosystems.
Priority: 1 (2009)
Compile Status Report; List under Wildlife Act; Send to COSEWIC; Planning; Habitat
CF Action
Protection; Habitat Restoration; Private Land Stewardship; Species and Population
Groups:
Management
a
Data source: B.C. Conservation Data Centre (2011) unless otherwise noted.
Identified Wildlife under the Forest and Range Practices Act.
c
This species is designated as wildlife under the B.C. Wildlife Act (Schedule A), which offers it protection from direct
persecution and mortality (Province of British Columbia 1982).
d
S = Subnational; N = National; G = Global; B = Breeding; X = presumed extirpated; H = possibly extirpated; 1 = critically
imperiled; 2 = imperiled; 3 = special concern, vulnerable to extirpation or extinction; 4 = apparently secure; 5 = demonstrably
widespread, abundant, and secure; NA = not applicable; NR = unranked; U = unrankable.
e
Data source: NatureServe (2010).
f
Data source: Ministry of Environment (2010b).
g
Six-level scale: Priority 1 (highest priority) through to Priority 6 (lowest priority).
b
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Recovery Strategy for Oregon Spotted Frog
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3 SPECIES INFORMATION
3.1 Species Description
Adult Oregon Spotted Frogs have black spots with light centres and fuzzy edges, scattered on a
brown or reddish-brown head and back region that becomes increasingly red with age
(COSEWIC 2000; Figure 1). Light brown to orange dorsolateral folds begin directly behind the
eye and run over the tympanum along the back. Beyond the middle of the back, the folds become
discontinuous and disappear as they approach the lower back. Juvenile Oregon Spotted Frogs are
olive green or light brown.
Figure 1. Adult female Oregon Spotted Frog. Photo credit: D. Knopp.
Adult Oregon Spotted Frogs often have a fragmented orange or red-orange colour on the
undersurfaces of the upper thigh and belly, and sometimes have dark spots mottling the belly
(Hayes 1997; COSEWIC 2000). The mean snout-urostyle length (SUL) of adult frogs captured
in Canada was 58.06 mm (N = 727; range = 38.48–80.21 mm; SD = 6.20) and the mean mass of
adult frogs was 20.98 g (N = 733; range = 5.90–55.36 g; SD = 7.60).
Although Oregon Spotted Frogs are most likely confused with Red-legged Frogs (Rana aurora),
they can be distinguished as follows:
• Red-legged Frogs have eyes that are angled outward; Oregon Spotted Frog eyes are
oriented upwards;
• Red-legged Frogs have flecks/freckles rather than spots and much brighter legs than
Oregon Spotted Frogs; and
• Oregon Spotted Frogs have completely webbed feet because they spend most of their
time in or around water, whereas Red-legged Frogs have partially webbed feet reflecting
their semi-terrestrial habits.
Both the Red-legged Frog and the Oregon Spotted Frog deposit eggs in March, although the
Red-legged Frog typically deposits its eggs 2–3 weeks earlier than the Oregon Spotted Frog. Egg
masses of the Oregon Spotted Frog are distinguished from egg masses of the Red-legged Frog by
the oviposition pattern. The Oregon Spotted Frog generally deposits egg masses in clusters
(rarely single), whereas the Red-legged Frog deposits single egg masses.
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Recovery Strategy for Oregon Spotted Frog
January 2012
3.2 Populations and Distribution
The Oregon Spotted Frog is a Pacific Northwest endemic whose historical range is from the Pit
River drainage in California, north to southwestern British Columbia (Figure 2). In the United
States, historical and extant populations are documented in the Puget Trough, in the Willamette
Valley, east in the south-central Cascades Mountains in Washington, in the central Cascade
Mountains of Oregon, and into the Pit River drainage of northeastern California. In British
Columbia, all historical and extant populations have been found in the Fraser River Lowlands
(Stebbins 1985; McAllister and Leonard 1997). In total, the Oregon Spotted Frog has been
documented at 103 localities across its North American range: 8 in British Columbia (4
extirpated, 4 extant; Figure 3), 19 in Washington (11 extirpated, 8 extant), 74 in Oregon (44
extirpated, 30 extant), and 3 in California (3 extirpated, 0 extant) (U.S. Fish and Wildlife Service
2009).
A population is delineated using the NatureServe occupancy criteria 1, separation distance, and
the maximum distance moved over suitable habitat for Oregon Spotted Frogs (see Habitat and
Biological needs section). Populations are considered independent if they are more than 1 km
apart over unsuitable habitat or greater than 3 kms apart over suitable habitat. This operational
definition of a population will be used to distinguish between separate populations’ but may be
redefined as more research becomes available. Locations are used to describe where a
population is verses sites which are within a population.
1
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely
recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of
one or more individuals (including larvae or eggs) in or near appropriate habitat where the species is presumed to be established
and breeding.
Separation Barriers: Busy major highway, especially at night, such that frogs rarely if ever cross successfully; urban
development dominated by buildings and pavement; habitat in which site-specific data indicate the frogs virtually never occur.
Separation Distance for Unsuitable Habitat: 1km
Separation Distance for Suitable Habitat: 5km
Reference NatureServe (2011).
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Recovery Strategy for Oregon Spotted Frog
January 2012
Figure 2. Present and historical distribution of the Oregon Spotted Frog in North America (adapted from
Hayes et al. 1997).
When this species was first assessed in 1994, there were 61 documented populations of the
Oregon Spotted Frog throughout its range. Of these 61 historically documented populations, only
23% or 14 populations remain: 1 in Washington and 13 in Oregon. In British Columbia and
California, none of the historically documented populations remain (Haycock 1998, 1999, 2000;
COSEWIC 2000). The Oregon Spotted Frog has disappeared from 70% (site count) to 90%
(area-based estimate) of its extrapolated historical global range (Pearl and Hayes 2005; Pearl et
al. 2005).
Currently, across its global range there are 38 extant populations in the U.S., including 8 in
Washington (1 historic, 7 new), and 30 in Oregon (13 historic, 17 new) (Pearl and Hayes 2005;
U.S. Fish and Wildlife Service 2009), and 4 extant populations in B.C., Canada.
Extant populations in British Columbia
In B.C., four extant populations of the Oregon Spotted Frog exist in the extreme southwestern
corner of the province, an area generally referred to as the Fraser River Lowlands (Figure 3;
Table 1). These populations are located in: the Department of National Defence property known
as Maintenance Detachment Aldergrove in the Township of Langley; (on federal land; this
population may be near extirpation); Mountain Slough and Maria Slough, both in Agassiz on
private and First Nations land; and a recently discovered population (2008) found on private land
in Morris Valley in Fraser Valley (locally referred to as Regional District Electoral Area “C”).
The four populations of Oregon Spotted Frog in Canada represent approximately 2% of the
global population of this species based on the 2009 egg mass census which found 153 egg mass
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Recovery Strategy for Oregon Spotted Frog
January 2012
in B.C., approximately 3000 in Washington and 5300 in Oregon (U.S. Fish and Wildlife Service
2009 census data). See Appendix 1 for population estimates at extant locations in British
Columbia. Note that the population at Maintenance Detachment Aldergrove is in danger of
becoming extirpated; no egg masses have been discovered at the location since 2006.
Extirpated populations in British Columbia
The Oregon Spotted Frog has been extirpated from four known locations (populations) in British
Columbia. Figure 3 maps these historic locations to the best of our knowledge based on site
descriptions. As site records contained nonspecific location data in the Sumas Prairie and
Nicomen Slough area, these locations are composed of several historic records/sites as their
exact locations are unknown.
1. Campbell Valley Regional Park in Langley Township (Licht 1971b). This population was
the subject of intensive study in the late 1960s (Licht 1969a, 1969b, 1971a, 1971b, 1972,
1974, 1975, 1986a, and 1986b). By the late 1990s, Oregon Spotted Frogs could not be
found at any of these sites (Haycock 1999). It is thought that the removal of livestock
grazing from the area negatively altered the habitat and allowed succession contributing
the extirpation of Oregon Spotted Frog (Haycock 2006).
2. Sumas Prairie area. There are four nonspecific site records of Oregon Spotted Frog in the
Sumas Prairie area including a remnant wetland of Sumas Lake near Sumas Prairie in
Abbotsford, recorded before the 1940s. This area has undergone significant changes
including the draining, damming and dyking of 33,000 acres that once was Sumas Lake in
1924 for agricultural use. Lakemount Marsh is one of the sole remnants of this historic
wetland/lake area.
3. Nicomen Slough area. There are three non-specific sites described for the Nicomen
Slough area including Nicomen Island in Matsqui, recorded before the 1940s.
4. West Creek wetlands. Glenn R. Ryder a well known local naturalist observed over 15
Oregon Spotted Frogs in West Creek Marsh / Wetland at Wood Duck Lake in Langley on
March 2, 1993 at the southeast end in the shallow grassy areas. Approximately 10 were
observed again on June 20, 1994 at a shallow backwater pool in the same area. This
location has never been reconfirmed and is now occupied by bullfrogs.
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Recovery Strategy for Oregon Spotted Frog
January 2012
Figure 3. Map illustrating location of four extant populations and four historical populations of Oregon
spotted frog. Map credit: Kristina Robbins.
Note that exact locations of the historic populations for Nicomen Island and Sumas Prairie are unknown
and so are represented by several site records (locations approximate).
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Recovery Strategy for Oregon Spotted Frog
January 2012
Table 1. Status and description of Oregon Spotted Frog populations in British Columbia.
See Appendix 1 for population estimates at extant locations in British Columbia.
Population
Status
Description
Land tenure
(habitat size)
Maintenance
Detachment Aldergrove
Extanta
(18 ha)
Township of Langley
Federal - Department
of National Defence
Mountain Slough
Extant
(20 ha)
Agassiz
Private and Crown
Maria Slough
Extant
(16 ha)
Agassiz
Private and First
Nations
Morris Valley
Extant
Floodplain wetland, Fraser Valley
Regional District Electoral Area “C”.
Private (future plans to
convert it to Crown
land- Wildlife
Management Area)
Historical (unknown)
Remnant wetland of Sumas Lake
near Sumas Prairie in Abbotsford,
recorded before the 1940s (Licht
1971b). Extirpated by the late 1990s
(Haycock 1999).
Private, Municipal,
Federal and First
Nations
Nicomen Island
Historical
•
Norrish Creek
Floodplain + delta
(unknown)
Matsqui, recorded before the 1940s
(Licht 1971b). Extirpated by the late
1990s (Haycock 1999).
First Nations, Private,
and Provincial Crown
•
Nicomen Slough
•
Mud Slough
(13 ha)
Sumas Prairie
•
Vedder Canal
Marsh
•
Vedder River
•
Vedder Canal
•
Sumas River
Campbell Valley
Regional Park
Historical
In Langley Township (Licht 1971b).
Extirpated by the late 1990s
(Haycock 1999).
Municipal
West Creek
Marsh/Wetland
Historical
Glen Ryder
Greater Vancouver
Regional District
Parks (Langley)
a
(30ha)
This population is in danger of becoming extirpated; no egg masses have been discovered at the location since 2006
Estimated change in population size in British Columbia
In comparison to numbers documented in Washington, populations in British Columbia are
extremely small. Egg mass counts in 1997, and 2000 to 2010 at locations in British Columbia
indicated that estimates of Canada’s entire breeding population varied between a low of 116
breeding adults in 2007 to a high of 548 breeding adults in 2002. The population estimate at the
known locations in Canada (including the recently discovered fourth location) was 316 breeding
adults in 2010. Several populations in the United States are much larger. However the US
populations have also experienced significant declines. For instance 7,018 egg mass were
recorded at Conboy National Wildlife Refuge, Washington, in 1998 but in 2009 it was down to
1,435 egg masses. The Trout Lake, Washington population has also decreased from 959 eggs
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Recovery Strategy for Oregon Spotted Frog
January 2012
mass in 2000 to 345 egg mass in 2009 (U.S. Fish and Wildlife Service Species Assessment form
April 2010).
In British Columbia, overall population size has fluctuated over the last 10 years. When
population trends are calculated based only on the 3 original known populations (Maria and
Mountain Sloughs, and Aldergrove and excluding the Morris Valley population which was
discovered in 2008), the overall population size has declined from 288 (1997) to 238 (2010)
(17% reduction; see Appendix 1).
3.3 Needs of the Oregon Spotted Frog
3.3.1
Habitat and biological needs
Adult Oregon Spotted Frogs are warm-water marsh specialists that prefer floodplain wetlands,
side channels, and sloughs associated with permanent water bodies and emergent vegetation
(Hayes 1997; McAllister and Leonard 1997). They prefer habitat with a large amount of open
water (low to moderate amounts of cover by emergent vegetation: 25–50%; Watson et al. 2003),
and appear to avoid areas with a gravelly substrate. Limited data from 2001 suggested that
Oregon Spotted Frog larvae (tadpoles) and juveniles used the shallow margins of wetlands in the
immediate vicinity of oviposition sites (R. Haycock, unpubl. data, 2001). Juvenile Oregon
Spotted Frogs were also frequently observed in shallow ephemeral pools beyond the margins of
permanent water (R. Haycock, pers. obs., 2001). Habitat requirements can be divided into three
life-seasons: breeding (oviposition) and early larval habitat, active summer habitat, and
overwintering habitat.
Breeding or oviposition microhabitats
Oviposition and breeding microhabitats are located in seasonally inundated warm shallows
(McAllister and Leonard 1997) associated with groundwater up-wellings, which provide
relatively stable thermal and water quality conditions (Figure 4). These sites are used for
courtship (when males call to females), mating, egg-laying, embryonic development, and
hatching. Larvae wriggle from their egg jelly, spend their early days clustered within the
remaining jelly egg mass substrate, and then disperse into the surrounding vegetation. Larvae are
not free swimming, and they grow and develop in the vegetation and substrate where they hatch.
As such, these microhabitats are critically important as a nursery for a portion of larval
development, and as a staging area for larval dispersal as water levels change. In these habitats,
water levels are typically lowest during egg-laying and rise with the annual rising of the Fraser
River; in systems not connected to the Fraser, waters may recede during this period.
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Recovery Strategy for Oregon Spotted Frog
January 2012
Figure 4. Typical oviposition habitat for Oregon Spotted Frog at Mountain Slough. Photo credit: K.
Welstead.
Egg masses are typically laid in communal clusters, although some egg masses are laid singly
(McAllister and Leonard 1997). Egg masses are deposited directly in the water on top of
vegetation or on the substrate (Pearl and Hayes 2004; R. Haycock, pers. obs., 1997, 2000–2003).
The number of masses per cluster varies widely. Licht (1969b) reported that clusters ranged from
5 to 26 masses, and McAllister and Leonard (1997) reported clusters ranged from 10 to 75
individual egg masses. The number of eggs per mass is also variable. In Canada, Licht (1974)
reported an average of 643 eggs (range 249–935) per egg mass at a now-extirpated population in
Campbell Valley Regional Park, and Haycock (COSEWIC 2000) reported an average of 670
eggs per mass at the Maintenance Detachment Aldergrove location. At the Dempsey Creek
population in Washington, egg masses contained 598 eggs on average (McAllister and Leonard
1997). The clustering of egg masses laid on top of each other in shallow water can result in at
least some of the egg masses being exposed to air.
Oregon Spotted Frogs select oviposition sites that meet specific requirements for water depth and
temperature. In British Columbia, the water depth at oviposition sites at the Maintenance
Detachment Aldergrove, Mountain Slough, and Maria Slough locations was 3–10 cm
(COSEWIC 2000). Older data from Licht (1969a) from an historic population at Campbell
Valley Regional Park indicated eggs were laid in water 5–12.5 cm deep. Across its range,
Oregon Spotted Frog oviposition sites have been discovered in water averaging between 5.9 and
25.6 cm deep (Pearl and Hayes 2004). These shallow margins of wetlands, ponds, and rivers
become quite warm (Licht 1971a; Figure 5). Water temperatures at the Maintenance Detachment
Aldergrove, Maria Slough, and Mountain Slough locations ranged from 4 to 14oC with an
average daytime temperature of 9oC (R. Haycock, unpubl. data, 2000). Similar ranges were seen
at the Maintenance Detachment Aldergrove location in 2005 where water temperature at
oviposition sites ranged from 3 to 18oC in early to late March, and at Maria Slough in 2007
where temperature ranged from 5.6 to 21.4oC at one location and 7.5 to 15.6oC at another in
early to mid-April (C. Bishop, unpubl. data, 2005, 2007). Licht (1971a) reported even warmer
temperatures, with an average water temperature of 17.6oC around egg masses at a nowextirpated population in Campbell Valley Regional Park. McAllister and White (2001) reported a
9
Recovery Strategy for Oregon Spotted Frog
January 2012
similar pattern in Washington, with daytime water temperatures at 6 sites averaging 16oC during
oviposition.
Figure 5. Oviposition site. The egg cluster in the foreground is coloured green by algae. A groundwaterfed spring inputs warmer fresh water adjacent to the cluster. Photo credit: K. Welstead.
The water bodies in which breeding and oviposition occur are connected to permanent water, and
are often dry in summer. However, at Maria Slough, Mountain Slough, and Morris Valley, water
levels are often lowest during the breeding season and rise throughout the summer. This is due to
the habitats’ connection to the Fraser River hydrograph, which is lowest in winter (as most of the
watershed’s precipitation is sequestered in snow and ice) and typically highest in June (as the
snow and ice melt in the Interior of British Columbia and drain into the Fraser River).
The permanent water connected to these oviposition locations can be fast-flowing or relatively
stagnant. The location is almost always vegetated with indigenous aquatic vegetation such as
rushes, sedges, grasses, pondweeds, and buttercups. Some of the plant genera found at these sites
include Scirpus, Juncus, Carex, Poa, Polygonum, Potamogeton, and Ranunculus. Other plants
present at these locations include the exotic grass of the genus Phalaris.
The timing of reproduction and egg-laying appears to vary with latitude and elevation
(McAllister and Leonard 1997). In British Columbia, the known breeding sites are all at low
elevation. Adults typically occupy the breeding sites from late February to late March, but in
cold years breeding and oviposition is delayed (Licht 1969a). Typically, several males first arrive
at the oviposition site sometime around late February each year, and call to females for as long as
1–3 weeks; the breeding season typically lasts less than 4 weeks (McAllister and Leonard 1997).
Mating is first initiated at or close to the breeding site. Eggs are laid and embryos develop from
late February to early April, and larvae develop and disperse from late March to late May (Licht
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Recovery Strategy for Oregon Spotted Frog
January 2012
1969a; R. Haycock, pers. obs., 2001–2003). In the United States, egg-laying occurred between
late February and late March at low elevation sites, but typically did not begin at higherelevation locations until the latter half of March (McAllister and Leonard 1997).
The onset of the breeding season is determined by temperature and day-length for other ranid
frogs (Duellman and Trueb 1986), and this pattern is likely true for Oregon Spotted Frog as well.
Licht (1969a) suggested that air temperatures of 5oC were required for Oregon Spotted Frogs to
emerge from their hibernation sites (Licht 1969a). Cushman and Pearl (2007) reported that frogs
at two sites in Oregon began breeding when water temperatures approached 10oC, although at
other locations, temperatures exceeded 10oC.
Frogs show strong site fidelity to oviposition sites. Licht (1969a) reported that Oregon Spotted
Frog oviposition sites used in 1969 were within 30 cm of those used in 1968. In Oregon, > 75%
of egg masses from two populations were discovered within 5 m of egg-laying locations from
previous years (Pearl and Bury, unpubl. data, cited in Pearl and Hayes 2004).
Active season habitat
Active season habitat, which is generally used in the summer months, includes warm, shallow
wetlands dominated by floating emergent vegetation (Licht 1971a; Hayes 1997). The results of
trapping (capture and release) and telemetry studies at the Maintenance Detachment Aldergrove,
Mountain Slough, and Maria Slough locations in late spring and summer indicated that adult
Oregon Spotted Frogs inhabited only the highly vegetated portions of wetlands (R. Haycock,
unpubl. data, 2001–2002), where vegetation was dominated by floating emergent Potamogeton
spp. interspersed with submergent Polygonum spp. Watson et al. (2003) also reported that
Oregon Spotted Frogs at Dempsey Creek, Washington, inhabited only very densely vegetated
portions of the wetland in the dry season; the dominant vegetation there was hardhack (Spiraea
douglasii).
Research indicates that active season sites are typically in deeper water than breeding sites. In
British Columbia, frogs were in water 42–112 cm deep in the active season, compared to
breeding habitat 3–10 cm deep (R. Haycock, unpubl. data, 2001–2002). Watson et al. (2003)
reported that summer frog locations were in deeper water (average 23.6 ± 1.0 cm) than water
depths at random locations (average depth 16.5 ± 1.0 cm), or oviposition sites (average depth
16.9 ± 0.6 cm).
Overwintering sites
Overwintering habitats provide a place where adults and newly metamorphosed juveniles (all
larvae mature before winter) hibernate and shelter from cold winter temperatures, and may be
occupied between October and late February. These habitats are different than those used during
the breeding and active seasons (Chelgren et al. 2006). Important characteristics of
overwintering sites are that they do not freeze, and that they have more stable levels of dissolved
oxygen than other areas (Pearl and Hayes 2004). Important habitats include springs, seeps, or
low-flow channels (Pearl and Hayes 2004), and frogs may bury themselves in silty soil or in
vegetation (McAllister and Leonard 1997). Watson et al. (2003) reported that frogs buried
themselves at the base of vegetation clumps, under ice < 5 cm thick.
11
Recovery Strategy for Oregon Spotted Frog
January 2012
Radiotelemetry data of frogs at the Maintenance Detachment Aldergrove, Maria Slough, and
Mountain Slough locations suggested that overwintering habitat might be associated with
beaver-altered habitat (R. Haycock, unpubl. data, 2001–2002), and Hayes et al. (2001) reported
that Oregon Spotted Frogs used beaver structures during winter. Frogs have also been reported
using ditch habitat in late fall or over winter (Watson et al. 2003; Pearl and Hayes 2004). Watson
et al. (2003) reported that water depth at overwintering locations was on average 17.4 ± 0.8 cm
deep. Pearl and Hayes (2004) provided data from other studies in Washington that reported mean
water depth at winter locations: Risenhoover et al. (2001) reported frogs at locations ranging
from 0 to 120 cm water depth (average 22 cm), Hallock and Pearson (2001) reported frogs in
water 1 to 88 cm deep (26.2 cm average), and Hayes et al. (2001) reported frogs in water from 6
to 111 cm deep (averages of 62, 49, 34, and 29 cm deep).
Aquatic connections between overwintering and breeding habitat during migratory periods in
late spring and fall are at minimum important, and may be essential (Watson et al. 2003; Pearl
and Hayes 2004). Known movements of Oregon Spotted Frog are almost exclusively along
water. Watson et al. (2003) found 99% of all telemetred frog locations (of 654) were in at least
1 cm of water. Additional evidence cited in Watson et al. (2003) in support of aquatic
movements was that they found no road-killed Oregon Spotted Frogs during their study (a road
blocked access to a major breeding pond, but there was access to the pond through a culvert
under the road), but did record Red-legged Frog and Pacific Chorus Frog (Pseudacris regilla)
mortalities. Although Watson et al. (2003) did report 1 overland movement of a frog, this
“overland” movement was through marshy swampy habitat, not dry upland habitat (M. Hayes,
pers. comm., 2008).
3.3.2
Ecological role
The Oregon Spotted Frog may serve as an indicator of the occurrence and health of shallow,
warm wetland habitats. Although other factors may contribute, the rarity of the Oregon Spotted
Frog probably coincides with the rarity of its habitat throughout its range. Accordingly, the
decline of the Oregon Spotted Frog is a likely indicator that shallow, warm aquatic habitats are
equally endangered. Within these habitats, Oregon Spotted Frogs may serve as a top predator of
aquatic invertebrates (e.g., Pearl et al. 2005) at the same time that they are a food source for
reptiles, mammals, and birds.
3.3.3
Limiting factors
Predators and elevated mortality rates
As a member of the lower levels of the food web, the Oregon Spotted Frog has many natural
potential predators. This placement in the food web makes it likely that Oregon Spotted Frog
population recovery may be influenced by a number of direct and indirect predator-induced and
trophic cascade effects that are not easily predictable. In addition, some of the predators listed
below are introduced predators (noted with an asterisk) and Oregon Spotted Frogs may not have
innate evolved anti-predator defenses. Other predators listed below are human commensals
whose population numbers increase in human disturbed areas and hence may increase predation
12
Recovery Strategy for Oregon Spotted Frog
January 2012
pressure on Oregon Spotted Frog populations beyond natural sustainable levels. These nonnative and human augmented predation pressures are addressed in the threats section.
Known and potential predators of various life stages of the Oregon Spotted Frog include, adult
and larval Dytiscid beetles (Dytiscus spp.), Backswimmer (Notonecta spp.), Leech
(Batracobdella picta), Odonate Nymph (Odonata), Water Scorpion (Nepidae), Bullfrog
(Lithobates catesbeianus),* Green Frog (Lithobates clamitans),* Garter Snake (Thamnophis
spp.), River Otter (Lontra canadensis), American Mink (Neovison vison), Great Blue Heron
(Ardea herodias), Green Heron (Butorides virescens), Belted Kingfisher (Megaceryle alcyon),
American Bittern (Botaurus lentiginosus), Northwestern Salamander adults and larvae
(Ambystoma gracile), Rough-skinned Newt (Taricha granulosa), Giant Water Bug (Lethocerus
americanus), Raccoon (Procyon lotor), Cutthroat Trout (Oncorhynchus clarkii), Red-tailed
Hawk (Buteo jamaicencis), Northern Harrier (Circus cyaneus), Hooded Merganser (Lophodytes
cucullatus), Great Horned Owl (Bubo virginianus), Red Fox (Vulpes vulpes), and Striped Skunk
(Mephitis mephitis) (Licht 1974; Pearl and Hayes 2004, 2005; Hayes et al. 2005; Watson et al.
2000, 2003).
Mortality rates of Oregon Spotted Frogs in the tadpole stage are high, and most likely due to
predation (Licht 1974; Hayes 1994b). Licht (1974) reported that tadpole mortality rates were
> 93% when he studied the now-extirpated population in Campbell Valley Regional Park. In
addition, juvenile Oregon Spotted Frogs may be more susceptible to Bullfrog predation than
northern Red-legged Frogs (Pearl et al. unpubl. data, reported in Pearl and Hayes 2004).
Adult males may have higher mortality rates than females; Licht (1974) reported that sexspecific mortality rates were significantly different ( i.e., 1-year survival rates of 45% for males
and 67% for females). He attributed the higher male mortality rates to their greater exposure to
predators during the breeding season, and their smaller size. Chelgren et al. (2006) also reported
higher mortality rates of males during the breeding season. Male Oregon Spotted Frogs are
present at breeding sites, where they are more exposed to predators, for 2–4 weeks while females
are present at the sites for only a short time (Licht 1974; R. Haycock, pers. obs., 2001–2003).
The smaller size of adult male Oregon Spotted Frogs, which are 46–60 mm compared to 62–
80 mm for females (Licht 1974), increases their susceptibly to predation, particularly from garter
snakes, which may be a very important predator of these frogs (Licht 1974). This potential
difference in survivorship of male Oregon Spotted Frogs may explain the absence of large males
at the Maintenance Detachment Aldergrove location (R. Haycock, unpubl. data, 2001–2003).
Risky oviposition site selection
The Oregon Spotted Frog’s selection of oviposition sites makes it particularly susceptible to
intermittently diminished recruitment that may result in an overall decline in population size.
Egg masses are deposited in the shallow margin of wetlands and are partially exposed to the air,
making the eggs susceptible to freezing, and desiccation from exposure to air and direct sunlight,
especially under windy conditions (Licht 1974; McAllister and Leonard 1997; Watson et al.
2000). In addition, oviposition sites are ephemeral and embryos are susceptible to desiccation if
water levels recede and strand the egg masses (Licht 1974; McAllister and Leonard 1997; R.
Haycock, pers. obs., 1997; Watson et al. 2000).
13
Recovery Strategy for Oregon Spotted Frog
January 2012
Habitat size
Based on data from occupied sites throughout its North American range, the minimum area
required to maintain an Oregon Spotted Frog population is 4 ha (Pearl and Hayes 2004). Larger
wetlands may be more likely to encompass the range of habitat types necessary to support a selfsustaining population that is better able to withstand high predation rates (M. Hayes, pers.
comm., 2008). Although Oregon Spotted Frogs have been reported from sites < 4 ha in the
United States, Pearl and Hayes (2004) suggested that these are remnant populations in areas that
were previously connected to larger areas of habitat. All of the currently occupied locations in
Canada are > 4 ha, but additional sufficient suitable habitat is scarce. Restoration of adjacent
habitat next to occupied sites may provide opportunities for the local populations to expand and
increase their population sizes. However, these opportunities are limited due to conflicting land
use activities.
Genetic isolation
The greater the isolation between sites, the lower the probability of genetic rescue from
dispersing individuals (Sjögren 1991). Thus, small populations may be at risk of inbreeding
depression and stochastic extinction (Sjögren 1991). It is possible that all of the current known
populations of Oregon Spotted Frog in Canada are genetically isolated. The mechanism of the
landscape-level dispersal of the species is not fully understood. There is some speculation that
the 100- to 200-year floods of the Fraser River may have historically played a role in allowing
Oregon Spotted Frogs to move through the lower Fraser Valley (K. Welstead, pers comm., 2008;
Figure 6). The current dyking and flood control systems in the area may inhibit long-distance
dispersal.
Figure 6. Map illustrating the floodplain area of the lower Fraser River (light blue area). The floodplain
overlaps with the historic and current extant range of the species. Map credit: Kristina Robbins
Oregon Spotted Frogs regularly move several hundred metres between breeding and winter
habitats. Watson et al. (2003) reported movements of Oregon Spotted Frog from 32 to 111
m/day for 2–18 days, which suggests that they are capable of longer-distance dispersal. A
telemetry study of Oregon Spotted Frogs reported that telemetred individuals did not usually
move more than 400 m from their original capture location (Hallock and Pearson 2001);
however, movements of > 1 km have been recorded within wetland complexes and along linear
14
Recovery Strategy for Oregon Spotted Frog
January 2012
riparian systems (Watson et al. 2003; Pearl and Hayes 2004). Two juvenile frogs were recorded
moving 1245 m and 1375 m, respectively, downstream from their initial capture location, and an
adult female was captured 2799 m (estimated stream distance) from her original capture location
(Cushman and Pearl 2007).
For Oregon Spotted Frog, aquatic connections between overwintering and breeding habitat are
essential (Watson et al. 2003; Pearl and Hayes 2004). Known movements of Oregon Spotted
Frog are almost exclusively along water. In Watson et al.’s (2003) study, 99% of all telemetred
frog locations (of 654) were in at least 1 cm of water. Based on telemetry data, Pearl and Hayes
(2004) suggested that all wetlands within 2–3 km of occupied locations be considered to have
increased potential as habitat for Oregon Spotted Frogs. This 2–3 km range would represent the
maximum expected movement for Oregon Spotted Frogs. Therefore, all known populations of
the Oregon Spotted Frog in Canada are likely isolated from one another; the distance between
the Morris Valley, Mountain Slough, and Maria Slough locations is about 8 km and each of these
locaitons is 50–60km from Maintenance Detachment Aldergrove. In addition, suitable wetland
habitat between any two locations is highly fragmented and movement between populations is
unlikely to occur.
Small population size and few sites
With only four remaining Canadian breeding populations and less than 350 estimated breeding
individuals, the risk of demographic and environmental stochastic events is high and could result
in further local extirpations. Given this, it is crucial that recovery efforts simultaneously include
both a small-population approach which addresses the effect of smallness on the persistence of a
population, as well as a declining-population approach which aims to diagnose the decline (the
reason the populations are small) and to resolve threats to the population (Caughley 1994).
Unfortunately, the Oregon Spotted Frog’s limited distribution in BC restricts the number and
availability of suitable recovery sites. Increasing the number of occupied locations (populations)
would help to mitigate stochastic events. However the fragmentation of wetlands in the highly
developed Lower Fraser River Lowlands will likely never allow for natural process such as
meta-population dynamics and colonization of new locations.
4 THREATS
Threats are defined as the proximate (human) activities or processes that have caused, are
causing, or may cause the destruction, degradation, and/or impairment of biodiversity and natural
processes. Threats presented here do not include biological features of the species or population
such as inbreeding depression, small population size, and genetic isolation, which are considered
limiting factors. Some of the limiting factors may be intrinsic but some (e.g. small populations)
are a direct result from historic or ongoing threats listed in this section and must be resolved
concurrently in order to recovery the species. Natural phenomena such as Geologic Events, and
Severe Weather (not related to climate change) are included in this definition, though should be
applied cautiously. These stochastic events should only be considered a threat when other
human-caused factors have reduced the population to such an extent that this type of event would
have a disproportionately large effect on the population compared to what they would have at
historic population levels.
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Recovery Strategy for Oregon Spotted Frog
January 2012
4.1 Threat Classification
The threat classification below is based on the IUCN-CMP (World Conservation Union-Conservation Measures Partnership) unified
threats classification system and is consistent with methods used by the B.C. Conservation Data Centre and the B.C. Conservation
Framework. For a detailed description of the threat classification system, see the CMP website (CMP 2010 1). For information on
how the scores are assigned or overall impact is calculated see Master et al. (2009) and table footnotes for details. Threats for the
Oregon Spotted Frog were assessed for the entire province (Table 2) 2 based on the best judgment of the Canadian Oregon Spotted
Frog Recovery Team in the absence of published information. Threats were considered at the four extant populations and at six
potential sites for Oregon Spotted Frog introduction/reintroduction in the next 10 years (see section 6.4.3, Table 4).
Table 2. Threat classification table for Oregon Spotted Frog.
Threat
number
Threat description
1
Residential & commercial development
1.1
b
b
Timing
d
Scope
Severity
Stress
Low
Restricted
Moderate
High
Low
Restricted
Moderate
High
Habitat loss
Low
Small
Slight
High
Habitat loss
Habitat loss
e
Commercial & industrial areas
1.3
Tourism & recreation areas
Low
Small
Slight
High
Agriculture & aquaculture
Annual & perennial non-timber
crops
Medium
Large
Moderate
High
Low
Large
Slight
High
Habitat loss
Livestock farming & ranching
Medium
Large
Moderate
High
Habitat degradation; Accidental mortality
Medium
Restricted
Serious
High
Medium
Restricted
Serious
High
Low
Large
Slight
High
2.1
2.3
3
3.2
4
Energy production & mining
Mining & quarrying
Transportation & service corridors
4.1
Roads & railroads
4.2
Utility & service lines
5
5.3
6
2
a
1.2
2
1
Housing & urban areas
Impact
Habitat degradation; Accidental mortality
Low
Large
Slight
High
Habitat degradation; Direct mortality
Unknown
Restricted
Unknown
High
Habitat loss
Low
Small
Slight
High
Logging & wood harvesting
Low
Small
Slight
High
Human intrusions & disturbance
High
Large
Serious
High
Medium
Restricted
Slight
High
Habitat degradation; Accidental mortality
Low
Small
Slight
High
Habitat degradation; Accidental mortality
Biological resource use
6.1
Recreational activities
6.2
War, civil unrest, & military
Habitat loss
< http://www.conservationmeasures.org/initiatives/threats-actions-taxonomies/threats-taxonomy/ >
Note that Appendix 2 summarizes specific threats and limiting factors for the four sites occupied by the Oregon Spotted Frog in a different format.
16
Recovery Strategy for Oregon Spotted Frog
Threat
number
Threat description
exercises
6.3
7
7.1
9.1
9.2
d
Natural system modifications
Medium
Restricted
Serious
High
Fire & fire suppression
Low
Small
Serious
Insignificant/
negligible
Invasive & other problematic species &
genes
Invasive non-native/alien species
Stress
e
Problematic native species
Habitat degradation; Accidental mortality
Habitat degradation; Direct mortality
Medium
Restricted
Serious
High
Habitat loss
Medium
Very HighHigh
Restricted
Moderate
High
Habitat degradation; Direct mortality
Pervasive
Very HighHigh
Pervasive
ExtremeSerious
Extremeserious
High
High
Habitat degradation; Direct mortality
Habitat degradation; Direct mortality
Low
Restricted
Slight
High
Pollution
Household sewage & urban waste
water
High
Large
Serious
High
Low
Restricted
Moderate
High
Direct and indirect mortality
Industrial & military effluents
Low
Restricted
Slight
High
Direct and indirect mortality
High
Large
Serious
High
Direct and indirect mortality
Unknown
Small
Unknown
High
Direct and indirect mortality
g
Low
Small
Slight
High
Direct and indirect mortality
Geological events
Low
Small
Moderate
High
Low
Small
Moderate
High
Low
Small
Serious
Moderate
Agricultural & forestry effluents
Air-borne pollutants
9.6
Excess energy
11
Timing
High
9.5
10.3
b
Serious
9.3
10
Severity
Large
Dams & water management/use
9
b
Scope
High
Other ecosystem modifications
8.2
a
Work & other activities
7.3
8.1
Impact
f
7.2
8
January 2012
Avalanches/landslides
Climate change & severe weather
Habitat degradation; Accidental mortality
11.2
Droughts
Small
Serious
Moderate
Low
Habitat degradation; Direct mortality
Impact – The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each stress is based on Severity and Scope rating
and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or
area decline for each combination of scope and severity corresponds to the following classes of threat impact: very high (75% declines), high (40%), medium (15%), and low (3%).
b
Scope – Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species’ population in the area of interest.
(Pervasive = 71–100%; Large = 31–70%; Restricted = 11–30%; Small = 1–10%)
c
Severity – Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10 year or three-generation timeframe. Usually
measured as the degree of reduction of the species’ population. (Extreme = 71–100%; Serious = 31–70%; Moderate = 11–30%; Slight = 1–10%)
d
Timing – High = continuing; Moderate = only in the future (could happen in the short term [less than 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in
the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting.
e
Stress – The condition or aspect (key ecological, demographic, or individual attribute) of the conservation target that is impaired or reduced by a threat (e.g., directly or indirectly results from human
activities).
f
Military exercises at Aldergrove.
g
Defined as inputs of heat, sound, or light that disturb wildlife or ecosystems. For Oregon Spotted Frog, this includes potential impacts from electromagnetic fields from transmission wires.
a
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Recovery Strategy for Oregon Spotted Frog
January 2012
4.2 Description of the Threats
The overall province-wide Threat Impact for this species is Very High 1. The greatest threat is
invasive non-native species (Table 2). At all occupied locations, the potential for specific threats
to cause a local extirpation is high due to small population numbers and isolation of populations
caused by habitat fragmentation. Details are discussed below under the Threat Level 1 headings.
4.2.1
Very high, high and medium impact threats
IUCN-CMP Threat 6. Human intrusions and disturbance
At the four extant locations, recreational activities do not pose a threat. However, at two of the
potential reintroduction sites, Grace Lake and Sasquatch Provincial Park, there are low impact
recreational activities such as canoeing and fishing. Military exercises may be conducted at
Maintenance Detachment Aldergrove, but such activities are rare, highly controlled, and not
conducted in the frog wetland. Consequently, they have minimal impacts on Oregon Spotted
Frogs or their habitat.
Work activities such as culvert maintenance and watercourse clearing can have a significant
impact on Oregon Spotted Frog populations at Maria Slough, Mountain Slough (and McCallum
ditch), and at the potential reintroduction sites at Prison Wetlands and the Agriculture Canada
Lands. Culvert blockages and clearing can result in habitat changes and water level draw down.
This has been recorded at Maria Slough where culverts were blocked in the spring and cleared
out during breeding season resulting in eggs stranded out of water. This can be avoided through
timing of culvert maintenance. Municipal in-stream maintenance works including ditch clearing
and deepening, which can reduce the availability and suitability of habitat, cause direct mortality,
and enable Bullfrog occupation and breeding.
IUCN-CMP Threat 8. Invasive and other problematic species and genes
In recent years there has been growing evidence that many amphibian declines witnessed on
three continents have been the result of chytridiomycosis and iridoviral infections (Daszak et al.
1999). It is suspected that the global spread of these diseases is the result of amphibian imports
and exports (Hanselmann et al. 2004). Chytridiomycosis has been reported from wild Oregon
Spotted Frogs in Washington and Oregon, but the full potential impact on populations is not yet
understood (Pearl et al. 2007). The causal agent of chytridiomycosis, Batrachochytrium
dendrobatidis, has been detected in introduced and native amphibians, including Oregon Spotted
Frog, from Maintenance Detachment Aldergrove and Maria Slough (P. Govindarajulu, pers.
comm.; unpubl. data, 2006–2009).
1
The overall threat impact was calculated following Master et al. (2009) using the number of Level 1 Threats
assigned to this species where Timing = High. This includes 1 Very High, 2 High, 3 Medium, and 4 Low (Table
3).The overall threat considers the cumulative impacts of multiple threats.
18
Recovery Strategy for Oregon Spotted Frog
January 2012
There have been a few instances of mass mortality of captive frogs in the head-starting program
(rearing of eggs and subsequent releasing of frogs to improve the chances of survival) in B.C.
that may have been caused by either water quality issues or iridovirus outbreaks (S. Raverty,
pers. comm., 2006). Iridovirus outbreaks in the most notable cases (i.e., Rana temporaria in the
U.K. and Ambystoma tigrinum in Saskatchewan and Arizona) appear to be related to high
densities of populations living in artificial or human-made habitats (Daszak et al. 1999). The
success of husbandry efforts depends on a better understanding of the iridovirus and any other
disease-causing organisms that may negatively affect wild and captive-reared populations.
Kiesecker and Blaustein (1997) found an increased occurrence of the Oomycete fungus
Saprolegnia in Cascades frog (Rana cascadae) egg masses in a study population in Oregon.
They reported that eggs laid in clusters had a higher mortality rate than those laid singly, and
thus species with communal egg-laying habits, such as the Oregon Spotted Frog, may be at
higher risk of Saprolegnia infection. Although B.C. populations have not been tested specifically
for Saprolegnia, it can be assumed to be present in all extant locations and potential sites given
the widespread distribution of this pathogen.
Although malformed Oregon Spotted Frogs have not been found at the 4 occupied sites in the
Fraser Valley, nor have malformations been linked to massive die-offs of this species (Daszak et
al. 1999), the potential exists for malformations to be of concern to the recovery effort. Four
cases of malformed Oregon Spotted Frogs have been reported to the North American Reporting
Bullfrogs and Green Frogs are exotic species in Western Canada. The Bullfrog is present at
Maintenance Detachment Aldergrove. Conversely, the Green Frog is present at Maria Slough
and Mountain Slough, but absent at Maintenance Detachment Aldergrove. No Bullfrogs or
Green Frogs have been observed at the Morris Valley site. Bullfrogs are opportunistic and
indiscriminate predators of reptiles, birds, mammals, and amphibians, including Oregon Spotted
Frogs (Licht 1974; Watson et al. 2003; Pearl and Hayes 2004). The Bullfrog is larger (snout–
vent length, approximately 200 mm; Duellman and Trueb 1986) than even adult Oregon Spotted
Frogs in Canada (maximum snout–vent length, 80 mm, average, 56 mm; N = 320) suggesting
that all size classes of Oregon Spotted Frogs, including adults, could be preyed upon by
Bullfrogs. Bullfrogs were recorded consuming hatchling Oregon Spotted Frogs at the
Maintenance Detachment Aldergrove site (R. Haycock and R.A. Woods, unpubl. data, 2001).
Adult Green Frogs (reach a snout–vent length of 100 mm; Duellman and Trueb 1986) may also
eat young Oregon Spotted Frogs, but adult Oregon Spotted Frogs may reach a size that is too
large to be prey for the species. Whether Green Frogs are significant competitors of Oregon
Spotted Frogs is currently unknown. It is also possible that the high population densities of
Green Frogs attract and maintain higher than normal population densities of native predators,
which in turn increase predation pressures on Oregon Spotted Frogs.
Reed canary grass (Phalaris arundinacea) was introduced to North America from Europe as a
cover crop and for use as silage. This clonal perennial propagates by underground rhizomes and
seed. It is typically found in dense stands in shallow water (< 15 cm), but has been observed as
floating mats in water as deep as 2.7 m (Lefor 1987); it occurs in water up to 2 m deep at the
Maria Slough site (R. Haycock, pers. obs., 2000). Reed canary grass is a particular threat to
native wetland species because of its rapid and aggressive growth, hardiness, and the difficulty of
19
Recovery Strategy for Oregon Spotted Frog
January 2012
selective control. Reed canary grass is present at the Maintenance Detachment Aldergrove,
Mountain Slough, and Maria Slough sites, but is not present in the area of sedge meadow that the
Morris Valley population occupies (D. Knopp, pers. comm., 2008).
Although the impact of reed canary grass on the suitability of habitat for Oregon Spotted Frog is
not fully understood, it appears that once the grass invades a shallow floodplain marsh, it
eliminates or reduces the amount of oviposition habitat available to the Oregon Spotted Frog
(COSEWIC 2000). Trapping and telemetry data collected at Maintenance Detachment
Aldergrove suggest that Oregon Spotted Frogs do not typically occupy homogenous stands of
reed canary grass (R. Haycock, unpubl. data, 2001–2002), although they may seek refuge in less
dense stands of reed canary grass when these stands are inundated with water. These clumps
provide the equivalent structural habitat to clumps of sedge (Carex spp.) and common rush
(Juncus effusus), which Oregon Spotted Frogs are known to inhabit (Watson et al. 2000; R.
Haycock, unpubl. data, 2001–2002). It is possible that the presence of the exotic, invasive reed
canary grass may increase the rate of natural succession and succession-related habitat loss.
Moderate cattle grazing may increase habitat suitability for Oregon Spotted Frog in reed canary
grass areas by breaking up vegetation mats and creating open habitat (Watson et al. 2000, 2003).
American Beaver (Castor canadensis) activity can influence the hydrology of the site. Both
positive and negative effects of American Beavers have been observed at sites in British
Columbia (COSEWIC 2000). American Beavers are present at all extant Oregon Spotted Frog
habitats in British Columbia. At Maria Slough, American Beavers may have a positive effect on
Oregon Spotted Frogs by encouraging water retention and providing overwintering habitat. At
Maintenance Detachment Aldergrove, American Beaver activity has led to higher water volume
retention and also resulted in the thinning of the canopy of forested wetlands, creating habitat
conditions that the Oregon Spotted Frog prefers. In Mountain Slough, where water levels
fluctuate during breeding season, American Beaver dams may stabilize water levels at certain
oviposition sites. At Morris Valley, channels used by Oregon Spotted Frogs and fish during low
water (paradoxically during the winter and spring when the wetland is not flooded) are likely
created by American Beavers.
American Beaver activity has also degraded habitat quality in some areas; approximately 300 m
of shallow wetland edge at Maintenance Detachment Aldergrove, where egg masses were laid in
the past, was eliminated by the creation of beaver impoundments between 1995 and 1999
(Haycock 2000). Typically, if dam-building activities eliminate oviposition habitat at an
occupied site, there is the possibility that they also create additional oviposition habitat elsewhere
because water backs up into new areas behind the impoundment. However, at Maintenance
Detachment Aldergrove, the topography behind newly created beaver dams is too steep to be
useful as oviposition habitat. Other areas that are appropriately graded are too densely vegetated
and unsuitable for oviposition.
IUCN-CMP Threat 9. Pollution
Water quality may be an issue for at least three of the currently occupied sites of Oregon Spotted
Frog. At Maintenance Detachment Aldergrove, fertilizers are not used which is in keeping with
the species management plan for this property (Haycock 2000); however, the wetlands occupied
20
Recovery Strategy for Oregon Spotted Frog
January 2012
by the Oregon Spotted Frog at Morris Valley, Mountain Slough, and Maria Slough are in largely
agricultural areas (Figure 7). For the 4 B.C. populations of Oregon Spotted Frog, chemicals most
likely enter the water from runoff from adjacent land use activities. Agricultural runoff includes
fertilizers (including manure) and runoff or percolation into the ground water from manure piles
(Rouse et al. 1999), and spraying of agricultural chemicals such as pesticides or insecticides
(including Btk, or Bacillus thuringiensis bacterium) or fungicides (used by blueberry producers),
including wind-borne chemicals. Water-borne sewage and non-point runoff from housing and
urban areas that include nutrients, toxic chemicals, and/or sediments are becoming an increasing
threat. Introduction of chemicals into waterways by chemical spraying during forestry activities,
maintenance of power line corridors, or disruption of normal movements of nutrients by forestry
activities (Lynch and Corbett 1990; Mayer et al. 2007) is also a potential source of
contaminations. Pesticides in the waterway can make frogs more susceptible to parasitic
infections and malformations, by negatively affecting their immune system (Kiesecker 2002) as
well as increased susceptibility to disease (toads; Taylor et al. 1999)..
There is a garbage dump upstream of the Maria Slough site and garbage has been illegally
dumped at sites at Mountain Slough and other sites that are close to human residential
developments. The impact of garbage (possible leaching pollutants) and solid waste on Oregon
Spotted Frogs is currently not known. The impacts of air-borne pollutants are unknown at the
sites.
Nitrogen. Like other amphibian species (e.g., Hecnar 1995; Rouse et al. 1999), Oregon Spotted
Frog is very sensitive to nitrogen in the environment in the form of nitrates, nitrites, or
ammonium found in agricultural fertilizers (Marco et al. 1999; Rouse et al. 1999). Marco et al.
(1999) suggested that this sensitivity might have resulted in the near extirpation of Oregon
Spotted Frogs from lowland areas in Washington, which have intensive agriculture use. Poor
water quality also exists within the Canadian range of the Oregon Spotted Frog. De Solla et al.
(2002) suggested that poor water quality, particularly due to high biological oxygen demand and
high levels of nitrogenous compounds such as ammonia and potentially organophosphate
pesticides, caused low hatching rates for 2 species of amphibians (Rana aurora and Ambystoma
gracile) at sites within the Sumas Prairie watershed in the Fraser Valley (an area of historical
Oregon Spotted Frog occupancy). McKibbin et al. (2008) found very low concentrations of
nitrate and total nitrogen in March and April during the Oregon Spotted Frog oviposition period
in 2 sites, Maria Slough and Maintenance Detachment Aldergrove. Although the nitrogen levels
in the spring were lower by orders of magnitude than those considered toxic to Oregon Spotted
Frog, the levels are likely to be much higher later in the season when fertilizers are applied to the
fields. Coliform bacteria levels were high in some sites and seasons and indicate high levels
of livestock waste runoff into Maria Slough. At present, there has been insufficient research
regarding impacts of high coliform levels on Oregon Spotted Frog.
Phosphorous may also impact wetlands. Phosphorous can enter the waterway from fertilizers
(including manure/solid waste) applied to agricultural fields or lawns, as well as from septic
fields or leaking sewer pipes. Phosphorous and nitrate inputs to wetlands have been linked to
parasitic infections in amphibians, which can lead to malformations (Johnson and Chase 2004;
Johnson et al. 2007). Because phosphorous typically attaches to sediment, buffer areas sufficient
to limit sediment deposition in the wetland should also be sufficient to limit phosphorous input.
21
Recovery Strategy for Oregon Spotted Frog
January 2012
Although a buffer can become saturated with phosphorous, at which point phosphorous will
leach into the waterway, the buffer will prevent large pulses (Wenger 1999).
Pesticides are a potential contaminant throughout the range of the Oregon Spotted Frog.
Pesticides can reach fairly high concentrations in wetlands in agricultural landscapes without
buffers. Wind-borne agricultural and forestry chemicals (such as insecticides or herbicides or
fungicides) have been linked to population declines of amphibians (Davidson et al. 2002). In
addition, exposure to chemicals such as carbaryl (insecticide) and atrazine (herbicide) can
negatively affect development of some species of anurans, and can also affect food resources for
some species of anurans (Hayes et al. 2002; Boone and James 2003). The herbicide glyphosate
(Vision® or Roundup® formulation) appears to be toxic at environmental levels to many
species of amphibians; however, the level of toxicity might be due to the surfactant in the
formulation rather than the active ingredient (Govindarajulu 2008). Anecdotal evidence suggests
that even taxon-specific biological pesticides such as Bacillus thuringiensis kurstaki - Btk and
Bacillus thuringiensis israelensis - Bti can cause mortality of aquatic amphibians, probably due
to additives to the pesticide such as surfactants and other non-active ingredients (P.
Govindarajulu, pers. comm.; unpubl. data 1999, 2003; C. Bishop, pers. comm., unpubl. data
2008). The scope of this threat is difficult to estimate and the impact is currently unknown.
Figure 7. Drainage into Mountain Slough between two oviposition sites. Photo credit: K. Welstead
Sediment deposition into streams and wetlands may potentially impact Oregon Spotted Frog
breeding habitat by changing the channel/wetland shape and depth. Potential sources of
sediment include runoff from adjacent agricultural fields, channel scouring, cattle tramping of
stream/wetland banks, road runoff, and runoff from adjacent forestry practices (Lynch and
Corbett 1990; Rashin et al. 2006). Retention of a protective area around the wetland and
watercourses can both trap sediment and help prevent it from entering the water.
Acid-leaching rock and iron influx from quarry activities may impact Oregon Spotted Frogs at
the Mountain Slough site. Iron is a common component of mine drainage, which can have a
22
Recovery Strategy for Oregon Spotted Frog
January 2012
detrimental effect on aquatic ecosystems. It can be present in several forms combining with a
variety of other ions. Impacts of precipitated iron are influenced by water pH and are generally
less severe in alkaline conditions. Ferric iron, when discharged to surface water, hydrolyzes to
produce hydrated iron oxide and more acidity. The acid lowers the pH of the water, making it
corrosive and unable to support many forms of aquatic life (Earle and Callaghan 1998). Dalzell
and MacFarlane (1999) found that the presence of iron at concentrations above 0.1 mg/L will
damage the gills of the fish as small particles of iron with dimensions of a few microns can
become trapped in the gill lamella potentially leading to secondary bacterial and fungal
infections. Ferric hydroxides decrease oxygen availability by coating gills and eggs, and cover
the stream bottom and alter the substrate, reducing prey availability (i.e., benthic invertebrates)
(Hoehn and Sizemore 1977).
Excess energy. Installation of a 500 kV transmission line directly above known oviposition sites
may cause maturation delays and reduced embryonic survival (Severini et al. 2003; Grimaldi et
al. 2004). A 500 kV transmission line passing through the Morris Valley habitat is currently offset from the oviposition sites. A twinning of this line is currently being proposed, which will
involve installing a line over the known oviposition sites. The impacts of electromagnetic fields
from transmission wires on amphibian are poorly studied, although a few studies indicate a
potential risk to the development of Oregon Spotted Frogs and therefore could be an emerging
threat. Metcalf and Borgens (1994) also found that voltages 25–75 mV/mm caused significant
developmental changes in gastrula and neuruola stage salamanders when they were exposed to
the electric field. The current right-of-way at Morris Valley has roughly the same magnetic field
conditions as that in the Metcalf and Borgens (1994) experiment; however, frogs at Morris
Valley will be exposed to the field throughout their life cycle. Because the lines at Morris Valley
will be doubled, and the oviposition locations of the Oregon Spotted Frogs will be directly
underneath the new line, it is possible that maturation delays will occur at that site if the project
goes ahead. The electric field below 500 kV lines by some estimates is predicted to be 10 kV/m
on the right-of-way and 2 kV/m at the edge.
4.2.2
Medium impact threats
IUCN-CMP Threat 2. Agriculture and aquaculture
Agricultural development in the Fraser River lowlands in the late 1800s and early 1900s required
the construction of dykes designed to stabilize fluctuating hydrological regimes of floodplain
habitats. Such activities have eliminated, or significantly limited, annual winter–spring wetland
renewal in floodplain areas, which has allowed natural succession (in the absence of flood
events) to proceed unchecked in these areas. This has resulted in a loss of Oregon Spotted Frog
habitat (COSEWIC 2000).
Agricultural land use changes, such as the conversion of field habitat to blueberry and cranberry
production, can lead to impacts through drain tile installation and riparian area
encroachment/erosion. Sediment deposition into streams and wetlands from runoff from adjacent
agricultural fields may potentially impact Oregon Spotted Frog breeding habitat by changing the
channel/wetland shape and depth (Lynch and Corbett 1990).
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Recovery Strategy for Oregon Spotted Frog
January 2012
Agriculture is an ongoing threat at Mountain Slough and to some extent at Maria Slough and
Morris Valley, and could be an issue at potential reintroduction sites at Agriculture Canada
lands, and the Mountain Slough habitat expansion sites.
Livestock use of riparian areas and access to watercourses or wetlands can affect bank stability
and result in increased sedimentation as well as nutrient loading, which degrades habitat quality
for Oregon Spotted Frogs. Livestock, primarily horses and cows, can also cause direct mortality
by trampling of egg masses. Livestock can also act as vectors for the introduction of weed seeds
that may alter riparian vegetation characteristics, and may be a potential source of parasite and
pathogen introduction or enhancement (Johnson et al. 1999). However, moderate cattle grazing
has been suggested to control invasive reed canary grass and preserve open habitat (Watson et al.
2000, 2003) but the threat of trampling should be weighed against the potential benefits.
IUCN-CMP Threat 3. Energy production and mining
Mining/quarry activities pose a potential risk because blasting can alter ground water
directionality, and may risk eliminating the water source in oviposition sites in some instances.
Mining on the steep hillside upstream of the Mountain Slough site has the potential of triggering
landslides and the sudden release of sediment into the wetland. Depending on the timing of this
event, it could have serious consequences to the population at this site. There are tentative plans
for gravel quarrying near the Maria Slough site; if these plans were to be realized, there is
potential for hydrological modification that would have severe impact on the Maria Slough
population (M. Pearson, pers. comm., 2009). This threat is acknowledged here even if the extent
of this threat is currently unclear.
IUCN-CMP Threat 7. Natural system modifications
Burning has been used for vegetation management at the Morris Valley site, potentially causing
direct mortality to adult frogs and egg masses/tadpoles as well as destruction of juvenile habitat.
Fire will no longer be used to control vegetation and increase forage for horses now that the
Oregon Spotted Frog population has been identified at the site. Thus the Canadian Oregon
Spotted Frog Recovery Team considers this a historic threat. It is unknown if previous fire
management actually helped maintain the vegetation characteristics that favoured Oregon
Spotted Frogs. This will need to be addressed as a knowledge gap and vegetation monitoring
should be implemented at the site.
Historic water diversions have occurred at Aldergrove for road construction and at Maria and
Mountain Sloughs for the development of agriculture. The impact of these historical diversions
probably resulted in loss of habitat but may have also provided some benefits. For example, at
Maria Slough several culvert structures create pinch points that separate the slough into cells that
favour the development of Oregon Spotted Frog habitat (S. Letay, pers. comm.). Concurrently,
these same water control structures likely prevent outmigration of individuals into unused but
suitable habitat areas downstream (M. Pearson, pers. comm., 2009).
Oviposition sites in shallow wetlands are susceptible to hydrological alteration. This can have a
devastating effect on Oregon Spotted Frog eggs and their habitat if there are sudden draw downs.
24
Recovery Strategy for Oregon Spotted Frog
January 2012
Additionally, the alteration of natural hydrological cycles due to the construction of water control
structures can result in the advancement of early seral vegetation into wetland shallows that no
longer flood, and may negatively affect Oregon Spotted Frog habitat. The most significant effect
of natural succession appears to be an overall reduction of suitable oviposition habitat (Chelgren
et al. 2006). Because of the growth of taller, denser vegetation at the periphery of wetlands, sites
appear to receive less solar radiation, resulting in lower water temperatures (R. Haycock, pers.
obs., 2001–2002). Movement studies suggest that Oregon Spotted Frogs do not use this altered
habitat (R. Haycock, unpubl. data, 2001–2002).
Flood prevention and overflow management may impact breeding habitat. The Hammersley
pump station at the Mountain Slough site is currently under review for upgrading. It is important
that significant drawdown does not occur especially during the breeding season. Diversion of
water from a site resulting in partial loss of water volume has the same effect as drought
conditions during oviposition and embryonic development. Current hydrologic conditions at
Mountain Slough show significant water level fluctuations during the breeding season, resulting
in egg mass movement and potentially heavy mortality in affected breeding areas (M. Pearson,
pers. comm., 2010).
Loss of riparian habitat that prevents erosion, sedimentation, and slow/absorbed runoff can also
greatly impact the habitat. In-stream or riparian works may result in sedimentation (e.g., channel
alteration, ditch maintenance, and fisheries work) directly impacting water quality and modifying
channel structure. Watercourse modifications can lead to large runoff events with a resulting
sudden influx of pollutants from the surrounding area.
Wetland restoration work, and in particular work designed to promote other species (such as
fish) can have serious impacts on Oregon Spotted Frog habitat by increasing habitat suitability
for competitors and predators. For example, the wetland restoration at Maintenance Detachment
Aldergrove is thought to have increased the population of Bullfrogs at the site. Fish focused
compensation works in occupied areas may inadvertently impact sites and may alter habitat
suitability. This includes riparian plantings, which may shade the water, altering water
temperature; changes in flow rate, which may reduce suitability and alter oxygen levels;
increases in large woody debris cover, which may increase the habitat suitability for Red-legged
Frogs (a sympatric species and potential competitor) and increase fish predation. Early seral
vegetation planted to enhance fisheries values is not compatible with the needs of Oregon
Spotted Frogs. These trees may grow to shade the site and/or decrease the availability of wetted
edge habitat due to water uptake (such as the planting of willows [Salix spp.] or red-osier
dogwood [Cornus stolonifera]) resulting in a loss of habitat for Oregon Spotted Frog. There has
been fisheries restoration work at Mountain Slough and Maria Slough. Closer collaboration
between various habitat restoration projects can greatly mitigate this threat.
4.2.3
Low impact threats
IUCN-CMP Threat 1. Residential and commercial development
Habitat loss as a result of human activities has occurred historically and is likely the
predominant, chronic, and widespread cause of the decline of the Oregon Spotted Frog
throughout its North American range (Hayes 1994a; Hayes 1997; McAllister and Leonard 1997;
25
Recovery Strategy for Oregon Spotted Frog
January 2012
COSEWIC 2000). Currently the sources of habitat loss and degradation due to rural and urban
development are site specific.
Removal or alteration of natural riparian vegetation around watercourses or wetlands for
development can compromise ecosystem function. Residential and commercial encroachment
may destroy or disturb natural vegetation, alter water flow and seasonal flooding, or result in the
loss of entire wetland complexes. Although the historic impact of this threat is high, it is
currently an ongoing threat at only a few sites: housing and residential developments at
Mountain and Maria Sloughs; commercial developments at Mountain Slough; and the recreation
activities at a potential reintroduction site at Sasquatch Provincial Park and Grace Lake.
Currently, the impact of development on Oregon Spotted Frogs is isolated to specific areas and
thus is ranked as low in BC, according to the IUCN threat classification system process (Table 2)
through the severity can be high if recommended best management practices (B.C. Ministry of
Water, Lands and Air Protection 2004) are not followed.
IUCN-CMP Threat 4. Transportation and service corridors
Historically, the impact of road building may have been high as many wetlands are bisected by
roads and railway corridors and the building of these roads changed the hydrology of wetlands.
However at the Maria Slough site, the building of an embankment, rather than a bridge, by the
Canadian National Railway upstream of Maria Slough cut off extensive seasonal flows into the
slough from the Fraser River. As a result, the north end, or upstream side, of Maria Slough
receives all of its water from groundwater and rainwater, instead of the historic flows from the
Fraser River. Without the building of the railway embankment, the current oviposition site at
Maria Slough would more than likely not exist, as it originally was a mobile channel of the
Fraser that was regularly flooded and deposited with gravel (M. Pearson, pers. comm., 2010).
Vegetation management along these transportation and service corridors could change wetland
characteristics and also be a source of pollution. Sediment deposition into streams and wetlands
from road runoff may impact Oregon Spotted Frog breeding habitat by changing water quality
and wetland characteristics (Lynch and Corbett 1990).
Populations at Maintenance Detachment Aldergrove, Maria Slough, and Mountain Slough are
close to roads but the severity of impact of these roads on Oregon Spotted Frogs is a knowledge
gap. Oregon Spotted Frogs are highly associated with wetlands and riparian areas and roadkills
may not be a threat to this species. However, roads may be preventing the expansion of extant
populations into nearby favourable habitats.
Hydro power transmission lines run across the Morris Valley site and the potential reintroduction
site at the Agriculture Canada lands. Maintenance of these utility corridors could pose a threat to
Oregon Spotted Frogs from pollution (such as paints, solvents, sedimentation, and other
pollutants from vehicles assessing the site) as well as increasing opportunities for the spread and
introduction of invasives, but the severity of the impact is currently not known.
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Recovery Strategy for Oregon Spotted Frog
January 2012
IUCN-CMP Threat 5. Biological resource use
Upslope forestry activities can increase sedimentation and nutrient loading. Sediment deposition
into streams and wetlands from runoff from adjacent forestry practices may impact Oregon
Spotted Frog breeding (Lynch and Corbett 1990). Logging could have a potential effect on
Oregon Spotted Frog habitat, especially at Mountain Slough where the hillsides are logged
before the start of mining and quarrying activities.
IUCN-CMP Threat 10. Geological events
Water quality at occupied sites may also be negatively impacted by runoff from natural cliff
erosion. Natural water chemistry may also influence Oregon Spotted Frog; McKibbin et al.
(2008) reported a correlation between embryonic survivorship and water chemistry, specifically
low chloride with attendant low conductivity. There is also the potential for catastrophic slope
failure and landslides at the Mountain Slough site that may release high levels of sediment into
the water and increase risk of smothering. The probability of landslides is great during high rain
events in the winter and spring which coincides with the overwintering and breeding seasons,
which are also the most vulnerable times in the Oregon Spotted Frog lifecycle. Another
geological event that may affect site characteristics at Maria Slough and Mountain Slough is
stream avulsion, where the stream channel is laterally displaced. These rare events are
unpredictable but could have significant impacts on the Oregon Spotted Frog population and
habitat characteristics. While these threats are acknowledged for completeness here, little can be
done to prepare for, or mitigate these threats.
IUCN-CMP Threat 11. Climate change and severe weather
Haycock (1999) speculated that climate change might be a threat to Oregon Spotted Frog
populations because of reduced spring water levels. Kiesecker et al. (2001) provided evidence
that climate change has resulted in reduced spring water levels at amphibian breeding sites in
Oregon, as a result of low winter precipitation. Pounds (2001) reported that higher air
temperatures and reduced water levels caused by climate change resulted in amphibian declines
in Costa Rica. Changes in water levels as a result of climate change and/or drought have the
potential to severely impact recruitment. As increased temperatures are known to affect the
survival and development of eggs and tadpoles (Licht 1971a), it is probable that climate warming
will affect this species.
Studies suggest that juvenile recruitment may be linked to spring rainfall; Watson et al. (2000)
reported that larval survival and recruitment were low when low rainfall in March and April
resulted in the elimination of outflow water from breeding ponds. In addition, both Licht (1974)
and Watson et al. (2000) reported that potentially high losses of embryos due to receding waters
were prevented only by researcher intervention.
The risk of drought at Maria Slough appears to be high. Maria Slough is fed by precipitation,
groundwater discharge from the Bear Mountain and Mount Hicks watershed to the northwest,
and hydraulic recharge from the Fraser River (Luttmerding and Sprout 1967). The water level at
Maria Slough depends on the water volume of the Fraser River. As evidenced in 2001, drought
conditions (Haycock 2001) reduced hydraulic recharge from all three sources and resulted in low
27
Recovery Strategy for Oregon Spotted Frog
January 2012
water levels in Maria Slough. The risk of drought at Mountain Slough also appears to be high,
but must be confirmed by further observation. Mountain Slough is spring fed, although the origin
of the spring water is poorly documented. Springs are visible in the main slough and originate
either from Fraser River hydraulic recharge, or groundwater discharge from the escarpment
above the slough, or a combination of sources. The risk of drought at Maintenance Detachment
Aldergrove may be high because it is situated at the top end of the watershed and has a very
limited catchment basin (S. Letay, pers. comm.). Although water levels at Maintenance
Detachment Aldergrove fluctuate, the hydrology at this site currently appears to be stable (ECL
Envirowest 2000; Haycock 2000). The risk of drought at Morris Valley is unknown. Note that at
all sites, the presence of drought conditions may result in water being diverted for human use,
thereby exacerbating the effects of drought at these sites.
The Oregon Spotted Frog extant sites along the Fraser River (Maria and Mountain Sloughs, and
Morris Valley) will all be prone to flooding events should they become more frequent with
climate change. Floods, especially during the breeding season, can have a significant effect on
the population, and even the free-swimming tadpole stages may be vulnerable to extreme flow
velocities.
5 RECOVERY GOAL AND OBJECTIVES
5.1 Population and Distribution Goal
The population and distribution goal (within 10 years) is
To restore, maintain and where feasible expand extant Oregon Spotted Frog populations, and
establish six or more additional self-sustaining populations in BC.
5.2 Rationale for the Population and Distribution Goal
There are only four Oregon Spotted Frog populations known in B.C. with less than 350
individuals. One of the populations (Maintenance Detachment Aldergrove) is possibly on the
brink of extirpation. An additional four populations are known to be extirpated. Each of the
extant populations is isolated from the other populations, and the probability of gene flow
between populations, or recolonization is extremely low. Suitable habitat within the range of the
Oregon Spotted Frog has been lost and degraded over time, largely as a result of land
modification for agricultural or urban development. Unless additional populations are created
through re/introduction to new and/or restored sites, the probability of species extirpation from
B.C. is considered high. The immediate goal is to prevent extirpation.
Habitat use pressures within the Oregon Spotted Frog range and the presence of introduced
species constrains the number of available new or reintroduction sites. Although 13 potential
sites are presented in Table 4, further investigation will likely reveal that several of these sites
are not suitable (e.g., may be too degraded to be effective for recovery). With this in mind, the
goal was set to establish 6 or more populations over the next 10 years. This would result in the
number of occupied locations increasing from 4 to a minimum of 10 locations. A minimum
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Recovery Strategy for Oregon Spotted Frog
January 2012
number of breeding adults at each location is needed to sustain viable populations. Until more
specific information is available, the population objective is 200 breeding adults per location. It
is recognized however, that the carrying capacity may limit what is achievable and as a result
targets will vary by location. In addition, it should be noted that the distribution objective may
slightly expand the species' range beyond the historic sites, due to introductions into suitable
habitat in the Fraser Valley that is not known to have been occupied in the past.
In the time it takes to establish new or reintroduced populations, existing individual populations
must remain stable or increase. This will hopefully be achieved through threat mitigation and
population augmentation. If successful, extirpation of the Oregon Spotted Frog will be
prevented. It may be possible for the COSEWIC designation to be upgraded from Endangered to
Threatened, but further improvement in conservation status is not expected given the limited
amount and fragmented nature of suitable habitat remaining for this species.
5.3 Recovery Objectives
The suggested timeframe to meet the long-term recovery goal is 10 years. However, the recovery
objectives 1, 2, 4, 5, and essential components of 6 should be achieved within the next five years.
The recovery objectives should be reevaluated every 5 years and updated as new information
becomes available.
The recovery objectives for the Oregon Spotted Frog are:
1. to prevent further habitat degradation/loss and population declines of Oregon Spotted Frog
by protecting 1, managing, and restoring habitat at all four occupied locations; at additional
occupied sites if found (see Objective 4), and at additional locations or sites established
through population introduction/reintroduction (see Objective 3)
2. to sustain or improve survivorship rates of all life stages of the Oregon Spotted Frog
where needed through threat mitigation, habitat restoration, and population augmentation;
3. to establish/re-establish self-sustaining populations at a minimum of six additional
historical, suitable, or restorable locations;
4. to prevent inadvertent loss of currently unidentified populations by conducting a
comprehensive inventory of potentially suitable habitat;
5. to determine the effectiveness of habitat protection/enhancement and population
augmentation/reintroduction measures by monitoring population status; and
6. to adaptively improve conservation and recovery efforts by addressing knowledge gaps in
the life-history, population ecology, threats, and habitat requirements of the species.
6 APPROACHES TO MEET OBJECTIVES
The actions recommended in the recovery strategy address threats or limiting factors to the
recovery of the Oregon Spotted Frogs in British Columbia or address the knowledge gaps that
1
Protection can be achieved through various mechanisms including: voluntary stewardship agreements,
conservation covenants, sale by willing vendors on private lands, land use designations, and protected areas.
29
Recovery Strategy for Oregon Spotted Frog
January 2012
currently hamper effective planning, implementation, or effectiveness monitoring of recovery
actions.
The Canadian Oregon Spotted Frog Recovery Team has five recovery implementation groups
(RIG) which address key threats and roughly correspond with our broad strategies. The RIGs
are: Habitat protection, management and restoration; Husbandry; Invasive species and Disease;
Recovery planning, Science acquisition information management and inventory/monitoring; and
Outreach/Stewardship.
6.1 Actions Already Completed or Underway
Recovery actions for the Oregon Spotted Frog in British Columbia have been underway for
several years. Below is a brief description of these action items listed by Conservation
Framework action groups. Additionally, specific action items completed at each occupied
location are listed separately at the end of this section.
Compile Status Report (complete)
• COSEWIC report completed (COSEWIC 2000). An update to the status report was
completed in 2010 and will be submitted to COSEWIC.
• Survey for Oregon Spotted Frog at historically occupied sites – 2000.
• Surveys for Oregon Spotted Frog in potential habitat in the Lower Fraser Valley – 1996,
1997, annual ongoing surveys since 2008.
Planning (in progress)
• B.C. Recovery Strategy completed (this document, 2011).
• Invasive Species Recovery Implementation Group (RIG) established and will assess and
implement as required Bullfrog and Green Frog control, reed canary grass management,
and disease monitoring and management (chytridiomycosis and iridovirus).
• Husbandry RIG established for captive rearing and head-starting of Oregon Spotted Frog
in captivity. Currently the RIG is assessing the feasibility and planning in conjunction
with the habitat RIG, population augmentation, reintroduction at historic sites, and
introduction at additional sites to ensure population persistence.
• Habitat RIG established and is currently assessing habitat and threats at extant and
potential reintroduction/introduction sites. This RIG is responsible for ongoing threat
mitigation at occupied, historical, and reintroduction sites; and habitat restoration at
potential re/introduction sites (see Table 4).
Species and Population Management (in progress)
• Habitat and ecological community assessments (including invasive species and disease
profiles) in potential reintroduction sites – ongoing since 2009.
• Captive assurance populations which help to retain genetic diversity initiated at the
Vancouver Aquarium and Toronto Zoo with ongoing maintenance.
• Captive rearing of wild collected eggs (mainly Maria Slough but also Mountain Slough)
to metamorphosis at the Greater Vancouver Zoo and Mountain View Conservation
Center.
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Recovery Strategy for Oregon Spotted Frog
January 2012
•
•
•
•
•
•
•
•
•
Monitor embryos for signs of predation, parasitic infection, fungal infection and other
maladies at occupied sites (ongoing).
Captive breeding of captively reared adults initiated at the Vancouver Aquarium and
Toronto Zoo – ongoing since 2010.
Release of metamorphic Oregon Spotted Frogs back into Maria Slough (year and
number): 2002 (354); 2003 (381); 2004 (836); 2007 (846); and 2008 (1012).
Release of metamorphic Oregon Spotted Frogs back into Maintenance Detachment
Aldergrove (year and number): 2005 (317) and 2006 (423).
Successful overwintering of metamorph Oregon Spotted Frog in mesocosms maintained
outdoors, which enabled a spring release of juveniles in 2009.
Second edition of captive husbandry manual in preparation (2009–2011). The first edition
updated with data from density, temperature, and feeding experiments conducted at the
captive rearing institutions (2005–2009).
Captive husbandry and reintroduction plan in development (2009–2011).
A review of other anuran population augmentation and reintroduction programs used
elsewhere (2010).
Survival habitat mapping has been draft at all occupied locations (2010) and modeling
complete for several potential recovery sites.
Habitat Protection, Habitat Restoration, and Private Land Stewardship (in progress)
Several specific activities have been completed, are underway, and/or ongoing at each occupied
location and are as follows:
Maintenance Detachment Aldergrove
• Egg mass enumeration – 1997, 2000, 2002 (ongoing).
• Management plan for the Oregon Spotted Frog – 2000.
• Habitat construction (1300-m2 pilot project) – 2001.
• Radiotelemetry – 2001 and 2002.
• Bullfrog gut analysis – 2002.
• Growth study – 2003 and 2004, Skeletochronology – 2003.
• Mark–capture–recapture study – 2001–2003.
• Habitat evaluation and identification of important habitat – 2002.
• Habitat design for habitat rehabilitation – 2002.
• Phase 1 site preparation for habitat rehabilitation – 2003 and habitat construction (18,000
m2) – 2004.
• Beaver management plan.
• Assessed the impacts of introduced Bullfrogs as predators and disease reservoirs – 2006
and removal of Bullfrogs – 2006–2008 (ongoing).
• Removal of reed canary grass (ongoing).
• Monitor water levels and ambient temperature (ongoing).
Maria Slough
• Egg mass enumeration – 1997, 2000, 2002–2011 (ongoing).
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Recovery Strategy for Oregon Spotted Frog
January 2012
•
•
•
•
Habitat construction (1500 m2) and habitat rehabilitation (1000 m2) – 2000. Habitat
construction (5000 m2) – 2009.
Post–egg-laying and summer season radiotelemetry –2003 and 2004. Post-release radio
telemetry of captive-reared frogs – 2009.
Translocation of 30,000 embryos to habitat construction site – 2002–2004.
Invasive reed canary grass species management – 2003.
Mountain Slough
• Egg mass enumeration – 1997, 2000–2002, 2004–2011 (ongoing).
• Radiotelemetry – 2005.
• Habitat construction (1800 m2) – 2005.
• Habitat rehabilitation – site rehabilitation including garbage removal, native riparian
vegetation restoration, and landowner stewardship contact program to encourage
stewardship activities – 2008–2011.
Morris Valley
• Egg mass enumeration – 2008–2011 (ongoing).
• Mark-recapture study (ongoing).
6.2 Knowledge Gaps
Further analysis and empirical investigation are required to clarify several threats and limiting
factors:
• Current species distribution: Although many wetlands within the range of the species
have been surveyed, others have not. Habitat suitability models and prioritized
inventories are required to protect important habitat, to develop specific recovery actions
(such as to promote connectivity between populations, to rehabilitate habitat, to identify
potential locations for population introductions), and to assess recovery progress.
• Minimum habitat size: What is the minimum habitat size required by Oregon Spotted
Frogs that is able to include all three seasonal microhabitats? Does the more northern
location of the Canadian populations influence the minimum habitat required?
• Habitat use: Refining our knowledge of the seasonal microhabitats used by Oregon
Spotted Frogs at the 4 known occupied locations in Canada? This knowledge will help to
assess future reintroduction and restoration initiatives, including restoration efforts for
multiple co-occurring wetland species-at-risk.
• Ability to move between habitat patches: The maximum distance that Oregon Spotted
Frogs move between habitats is 3 km (Pearl and Hayes 2004) along an aquatic corridor.
What are barriers to movement of Oregon Spotted Frogs? What are ways to mitigate
potential barriers? The Oregon Spotted Frog requires an aquatic corridor to move
between habitat patches. What is the habitat composition between known B.C.
populations of Oregon Spotted Frog?
• Captive breeding/introduction: Recently we have started a successful captive breeding
program which involves captive adults mating and fertilizing eggs in captivity. This
program will be developed and a protocol on captive breeding will be developed as more
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Recovery Strategy for Oregon Spotted Frog
January 2012
•
•
•
•
•
•
research is completed, gaps included but are not limited to issues of tracking provenance,
potential disease, age, treatments etc.
Captive rearing/husbandry: Captive rearing involves rearing of all life stages of Oregon
Spotted Frogs. The effectiveness of the captive rearing program in improving
survivorship and augmenting populations needs to be evaluated.
Predation and disease: The level of threat from Bullfrogs and Green Frogs and the
necessity for mitigation of these non-native predators is poorly understood. The potential
diseases that may affect wild and captive-reared populations in B.C. are poorly known.
Encroaching vegetation/natural succession: The level of threat to suitable habitat
presented by encroaching vegetation, including reed canary grass, is poorly understood.
Also, what is the most practical and economically feasible way of controlling unwanted
vegetation? Could grazing improve habitat for Oregon Spotted Frog in areas of reed
canary grass by breaking up vegetation mats and creating openings (as per Watson et al.
2000, 2003) or should reed canary grass be actively managed using mowing, shade,
and/or competition with native vegetation?
Hydrological alteration: The effects of hydrological alteration by beavers or
anthropogenic structures and the creation or elimination of Oregon Spotted Frog habitat
is poorly understood. The elevated water levels following beaver dam construction or
other man-made blockage may eliminate shallow breeding habitat but the retention of
water may increase summer foraging habitats and dam structures may provide
overwintering habitat. As all the extant Oregon Spotted Frog populations occur in
habitats with potentially increasing beaver activity, the interaction between beavers and
Oregon Spotted Frog habitat needs to be better understood.
Impacts of electromagnetic radiation on embryo development: An electrical transmission
line will be built in Morris Valley in the next few years, and the transmission line will run
directly over the traditional mass oviposition site of the Oregon Spotted Frogs. This
breeding site will need to be monitored to assess if electromagnetic radiation from the
transmission line affects growth or survival of the Oregon Spotted Frog embryos.
Baseline data on embryo survival are currently being collected.
Climate change: The long-term impact of climate change on the Oregon Spotted Frog is
not clear. Changes in rainfall and temperature associated with climate change will
potentially have hydrological impacts on this species that depends on permanent shallow
wetland habitat.
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Recovery Strategy for Oregon Spotted Frog
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6.3 Recovery Planning Table
Table 3. Recovery planning table for Oregon Spotted Frog in British Columbia.
Target
Objective
#
Approaches to meet objectives
Threata or
concern
addressed
Priorityb
Habitat Protection
1, 2, 3
4
1,2,5
1, 4, 5,
6
Habitat Protection and Management:
• Update and refine survival habitat mapping/polygons
(includes occupied locations) annually. Finalize
recovery habitat spatial definition/ mapping and provide
results to relevant agencies and land users and initiate
consultation.
• Protect, maintain, improve, expand and/or restore the
area, extent and quality of seasonally occupied habitats
(e.g. oviposition sites, overwintering sites, and active
summer habitat) at occupied and potential recovery sites
(see Table 4).
• Mitigate direct and indirect threats to Oregon Spotted
Frogs and eggs. Address direct and indirect threats to
survival and recovery habitat. Minimize or eliminate the
threat factors that limit habitat suitability or
connectivity.
Inventory and monitoring:
• Use surveys at extant locations and radio-telemetry data
to develop habitat suitability models to prioritize
surveys to find currently unknown populations.
• Conduct surveys to further determine range of Oregon
Spotted Frog and its presence at potentially suitable
habitats.
• Incorporate information on land use and landscape
features to identify potential threats to habitat.
• Monitor habitat quality and respond to signs of
degradation as appropriate.
• Describe, monitor (for threats and changes), and report
on the biophysical, chemical, and microclimate
characteristics of seasonal habitats at currently
occupied, historical, and newly established sites.
1, 2, 3, 4, 5, 6, 7;
Knowledge gaps
Essential
Knowledge gap
Essential
Knowledge gap
Essential
All threats
Essential
1, 2, 3, 4, 5, 6, 7
Knowledge gap
Essential
1, 3, 4, 5, 6, 7, 8
Essential
2, 9
Essential
1, 2, 3, 4, 5, 6, 7,
8, 9
Necessary
All threats
Essential
Land Stewardship
1, 2, 5
•
•
•
•
Work with all levels of government, land managers, and
private landowners to inform and encourage best
practices and ensure compliance in relation to water
quality, hydrology, and land use practices.
Coordinate with the Ministry of Agriculture to
implement supporting farming practices and
environmental farm plans options to decrease agrochemical and nutrient pollution into Oregon Spotted
Frog aquatic habitats.
Develop, promote and implement Best Management
Practices (BMPs) for Oregon Spotted Frogs and
watershed management and monitoring plans.
Develop and implement site management plans for
34
Recovery Strategy for Oregon Spotted Frog
January 2012
Target
Objective
#
1,3,4
Approaches to meet objectives
occupied locations addressing site-specific threats and
developing site-specific mitigation measures.
• Work one-to-one with willing landowners/managers to
mitigate threats (e.g., fencing of riparian areas to
prevent disturbance by people, pets, and livestock;
pollution reduction). Where there are willing
landowners implement formal conservation covenants
or stewardship agreements.
• Work with local governments and other agencies to
ensure in stream works and ditch maintenance impacts
are mitigated, e.g. ditch clearing, and maintenance of
culverts, utility pipelines etc..
Information management and outreach:
• Maintain a current database and a map delineating
survival and recovery habitat that is easily available as a
SHAPE file to all levels of government and other land
managers to prevent inadvertent impacts to Oregon
Spotted Frog habitat.
• Build public and stakeholder support for recovery
activities by increasing understanding and promoting
responsible behaviour toward wetland conservation, and
amphibians, among all levels of governments, natural
history groups, volunteers, general public, and private
landowners
Threata or
concern
addressed
Priorityb
Knowledge gaps
2, 7, 8, 9
Essential
6, 7
Essential
1, 2, 3, 4, 5, 6, 7
Essential
1, 2, 3, 4, 5, 6, 7
Essential
2, 9
Essential
All threats,
Knowledge gaps,
Limiting factor
Essential
Habitat Restoration
1, 2, 3
3
Restore habitat and connectivity:
• Identify and map priority areas for protection,
management, and rehabilitation to promote habitat
connectedness throughout range and to allow dispersal
of the species. Where possible protect connecting
habitat between occupied locations with the goal of
restoring natural migration dynamics. Coordinate with
regional districts, municipalities, and forest licensees to
promote connectedness among riparian habitat through
landscape-level planning.
• Improve water quality through restoration, monitoring,
and increased compliance to regulations. Monitor water
quality and quantity (levels) in partnership with
agencies to ensure a natural hydrologic state.
• Where necessary restore and enhance habitat at priority
sites for introductions/reintroductions. Where feasible,
initiate habitat restoration including creation of
appropriate breeding and other seasonal habitats,
restoring hydrological conditions, establishing habitat
connectivity among seasonal habitats. Coordinate with
stewardship groups and DFO to incorporate habitat for
Oregon Spotted Frog into rehabilitation projects.
Develop guidelines for habitat rehabilitation and
distribute to funding bodies and agencies (e.g.,
Canadian Department of Fisheries and Oceans, Habitat
35
Recovery Strategy for Oregon Spotted Frog
January 2012
Target
Objective
#
5, 6
2, 3, 5,
6
1, 2, 3,
5, 6
2, 6
2, 6
Approaches to meet objectives
Conservation Trust Fund) for implementation to avoid
conflict with fisheries compensation activities and other
works.
• Monitor and evaluate newly created and enhanced
habitats.
• Investigate a multi-species approach when considering
enhancing existing habitats and creating new habitats.
Native habitat maintenance, invasive species and disease
management:
• Monitor natural succession and vegetation changes to
assess the impact of this natural process on the
availability of essential habitat for Oregon Spotted
Frogs
• Maintain habitat conditions for all life stages. Manage
the availability, size and number of oviposition sites
through control of encroaching vegetation. Monitor
ambient water temperature and habitat conditions.
• Control colonization and overgrowth of habitat by reed
canary grass where it has compromised oviposition
sites. Plant competing native species to mitigate
colonization of reed canary grass.
• Assess the relative risk of invasive predators and
evaluate predator control and mitigation strategies for
managing introduced predator risk.
• Monitor and map bullfrog populations and initiate
control measures where feasible. Reduce habitat
suitability for bullfrogs and where feasible reduce
population numbers. Outreach messaging to not move
bullfrogs and other non-native species.
• Assess and monitor parasite and disease threats.
Threata or
concern
addressed
Priorityb
All threats,
Knowledge gaps
Necessary
7, 8;
Knowledge gaps
Necessary
8
Necessary
8;
Knowledge gaps
Necessary
Limiting factors
Essential
Limiting factors
Essential
Limiting factors;
Knowledge gaps
Essential
Limiting factors;
Knowledge gaps
Essential
Limiting factors
Necessary
Species and Population Management
1, 2, 3
2
3
3
3
Protect all life stages and population augmentation:
• Maintain assurance populations from the extant
populations to archive genetic pool.
• Augment declining populations to stabilize egg mass
productivity and restore known/historic populations.
• Develop a reintroduction plan that incorporates capacity
of husbandry facilities to produce animals for
reintroduction, a prioritized list of potential
introduction/reintroduction sites, recommendations for
effective strategies for establishing self-sustaining
populations and cost/resource budget for implementing
the plan.
• Improve and refine captive head-starting and captive
breeding techniques, so that sufficient numbers of
animals of various life-stages are available for
reintroduction programs.
• Consolidate captive rearing and husbandry capacity by
establishing agreements with zoos, aquaria, and other
rearing institutions.
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Recovery Strategy for Oregon Spotted Frog
January 2012
Target
Objective
#
3, 6
Approaches to meet objectives
•
Threata or
concern
addressed
Priorityb
Conduct genetic analyses to estimate the effective
population size, rates of dispersal, and mixing among
populations, and levels of inbreeding. This knowledge is
essential to determine the genetic composition
necessary to establish the most viable Oregon Spotted
Frog populations at new and historic sites.
Introduction/ reintroduction:
• Ensure at least 6 additional viable populations are
secured through Oregon Spotted Frog range in B.C. by
(1) introducing Oregon Spotted Frogs to priority new
suitable sites within the Fraser River Lowlands; and (2)
reintroducing Oregon Spotted Frogs to priority
historically occupied habitats.
Population Monitoring:
• Establish population monitoring at all occupied
locations to estimate baseline population parameters
using capture-mark-recapture, radio-telemetry, and
other suitable techniques. Quantify population
demographics using sensitivity analyses, population
viability, and assessment models. Use the output from
these models and field based results to improve
sustainability of extant populations and increase
probability of establishment of introduced populations.
Research
• Evaluate the risk of electromagnetic fields under high
tension wires on development and survival of Oregon
Spotted Frog embryos.
• Monitor the impacts of climate change on Oregon
Spotted Frogs
Limiting factors;
Knowledge gaps
Necessary
Small
populations;
Limiting factors
Essential
Knowledge gap
Necessary
Knowledge gaps
Essential
5, 6
•
Knowledge gap
Essential
5, 6
•
Knowledge gaps
Necessary
3, 5,
1, 2, 5,
6
6
Necessary
Planning
•
Monitor and report on extant population health and
survivorship at all locations annually including
monitoring and evaluating all introduced and
reintroduced populations.
Continue to collaborate on habitat assessment and
recovery planning and implementation with
conservation biologists and recovery teams in
Washington and Oregon.
Resource acquisition, secure funding and other
resources needed to implement recovery actions.
a
Threat numbers according to the IUCN-CMP classification (see Table 2 for details).
Essential (urgent and important, needs to start immediately) and Necessary (important but not urgent, action can start in 2–5
years)
b
6.4 Description of the Recovery Planning Table
Recovery implementation should include considerations at the landscape level and incorporate
other species at risk values whenever possible. However, because of the unique habitat and
biological needs of the Oregon Spotted Frog, it is recommended that a single-species approach
37
Recovery Strategy for Oregon Spotted Frog
January 2012
be taken to implement recovery actions in most cases. Where possible, all recovery activities
should be conducted as experiments using an adaptive management model to determine their
effect and efficacy in reaching the desired recovery objectives and to improve subsequent
recovery actions.
6.4.1
List under Wildlife Act
It is recommended that this species be listed as Endangered under the British Columbia Wildlife
Act. This would assist in the conservation of the species by heightening the significance and
profile of this species.
6.4.2
Habitat Protection, Land Stewardship and Restoration
A number of protection and threat mitigation measures will be needed to protect the Oregon
Spotted Frog. This may include legislative protection (e.g., Protected Areas, Wildlife Habitat
Areas, landscape management plans) and non-legislative protective means (e.g., best
management practices, stewardship agreements). Existing legislative tools include the Wildlife
Act which offers this species protection from direct persecution and mortality and other tools that
indirectly offer some protection (e.g., Fisheries Act, provincial Water Act, Environmental
Protection Act and Riparian Areas Regulation). For additional information on protection refer to
http://www.env.gov.bc.ca/wld/faq.htm#17.
For successful implementation of protection for the Oregon Spotted Frog, there will be a strong
need to engage in stewardship on a variety of land tenures, and in particular on private land.
Stewardship involves the voluntary cooperation of landowners and managers to protect species at
risk and the ecosystems they rely on. This stewardship approach will cover many different kinds
of activities, including: following guidelines or best management practices to support species at
risk; voluntarily protecting important areas of habitat; conservation covenants on property titles;
eco-gifting of property (in whole or in part) to protect certain ecosystems or species at risk; or
sale of property for conservation.
Restoration of adjacent habitat next to occupied locations may provide opportunities for the local
population to expand and increase its size. Although opportunities may be limited due to
conflicting land use activities, this option should be investigated around the locations of all
known, newly discovered populations and introduced populations.
6.4.3
Species and Population Management
There are four extant populations of Oregon Spotted Frogs in B.C. Of the 4 populations,
Maintenance Detachment Aldergrove has the most protected habitat as it is on lands managed by
the Department of National Defence, and yet the numbers of Oregon Spotted Frogs at this
location have declined with no breeding activity observed since 2007. Given the fluctuating
numbers in the other three populations and the inability of habitat protection alone to recover this
species, additional recovery measures are required.
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Recovery Strategy for Oregon Spotted Frog
January 2012
The low numbers of individuals at the four extant locations mean that these populations are
vulnerable to even moderate increases in mortality rates from introduced predators, disease, and
parasites that larger populations may be robust enough to sustain. The collaboration with
academic researchers to gain a better understanding of population ecology, demography, genetics
of small populations, and impacts of introduced predators, parasites, and disease is
recommended.
The Canadian Oregon Spotted Frog Recovery Team recommends the government maintain
assurance populations in captivity, and support captive rearing/breeding and re/introduction
program to both increase the size of current populations (i.e., augmentation) and to establish
populations at new and historic sites within B.C. (i.e., re/introduction).
The locations of potential introductions (to establish new populations), reintroductions (to reestablish populations at historic sites), and population expansions (sites adjacent to existing
populations that will expand the extant of that population) have not been finalized; however, the
recovery team is currently considering the sites listed in Table 4 for re/introduction though others
may be added to the list. Re/introduction is not guaranteed at these sites and will proceed only
after appropriate consultation with stakeholders, and finalization of studies to determine their
suitability.
Table 4. Potential introduction, reintroduction or population expansion sites for Oregon Spotted Frog in
B.C. Sites that have an * were used in the threat scoring.
Site
Description
Potential introduction sites – new populations
Chaplin Road site * Chaplin Road site was modified in
2009 and 2010 to increase available
wetland habitat.
Grace Lake
North East of the Morris Valley site
Sasquatch
Wetlands areas around Deer Lake,
Provincial Park*
Moss lake and Hicks Lake.
Cheam Lake* and
Adjacent to the Cheam Wetland –
Chehalis wetland
human-made lake with wetland areas
West of Cheam Lake
Opsee
Chilliwack low elevation expansive
wetlands overlapping with Pacific
Water Shrew habitat.
Agriculture and
Wetlands at the Agriculture Canada
Agri-Food Canada
lands in Agassiz. The UBC Farm 2
Research Station /
lands occupy a south facing valley that
UBC Farm 2 *
drains into Maria Slough.
Potential reintroduction sites – historic populations
West Creek Marsh* Historic site and a protected wetland
area. There is a healthy bullfrog
population at this site
Land tenure
Provincial Crown land
Provincial Crown land
Sasquatch Provincial Park
FVRD Park
First Nations
Provincial Crown – lease to
Department of National
Defence
Agriculture Canada leased to
the University of British
Columbia (UBC) Agassiz
Research
FVRD Park
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Recovery Strategy for Oregon Spotted Frog
January 2012
Site
Nicomen Slough
Sumas Prairie –
Sumas River and
Lakemount Marsh
Campbell River
Description
Historic site
Potentially suitable habitat when
combined with Lakemount Marsh.
Possibly the Great Blue Heron Nature
Reserve Lagoon and adjacent wetland
areas on the Sumas River.
Historic site - may require
rehabilitation
Land tenure
Private
24% privately owned, 72%
provincial Crown land
(BCLAND)
72% privately owned, 28%
municipally owned (GVRD
Parks)
Potential population expansion sites
Corrections Services A potential wetland restoration site
Correctional Service of
Canada Mountain
adjacent to Mountain Institution on
Canada
Institution*
Mountain Slough. The Mountain
Institution is a medium-security
federal facility located in Agassiz
approximately 800 meters from known
existing Mountain Slough Oregon
Spotted Frog Population
Aldergrove –
Continue wetland habitat and
100% privately owned
adjacent sites to
restorable areas within the occupied
Maintenance
site as well as the site across the road
Detachment
by the mushroom farm that has a
Aldergrove (DND)
previous Oregon Spotted Frog
occurrence record – Libor 2002
6.4.4
Planning
We recommend that site-specific management plans be developed and implemented for all
currently occupied locations. Management plans should focus on protection of populations and
habitat from land use activities, and threats specific to each location. Appropriate protection
measures and management plans should be put in place for all introduced/reintroduced and
newly discovered populations.
A summary of the spring egg mass counts and trapping surveys is prepared each year for all 4
extant populations. Amphibian populations are naturally prone to large fluctuations in size and at
small population sizes are prone to local extirpations due to stochasticity. Annual monitoring of
populations is essential for determining conservation status of each population.
Oregon Spotted Frogs are declining throughout their global range. Close collaboration with
recovery efforts in Oregon and Washington increases technical and scientific capacity for
addressing knowledge-gaps and assessing cost-effectiveness of recovery efforts.
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Recovery Strategy for Oregon Spotted Frog
January 2012
7 INFORMATION ON HABITAT NEEDED TO MEET RECOVERY GOAL
Threats to Oregon Spotted Frog habitat have been identified and habitat is limiting for this
species. To meet the population and distribution goal for Oregon Spotted Frog in B.C., it is
necessary to know the specific habitat requirements of this species. In addition, it is necessary to
geospatially describe the locations of the habitat on the landscape to mitigate habitat threats and
to facilitate the actions for meeting the population and distribution goal.
7.1 Description of Survival/Recovery Habitat
In the following sections the habitat needed for survival and recovery of the species is defined
(Section 7.1.1), biophysical attributes described (Section 7.1.2) and the procedure to describe
both survival and recovery habitat is presented (see Section 7.1.3). Appendix 3 provides maps of
survival habitat at four locations where Oregon Spotted Frog is known to occur. However, as
these areas of survival habitat are expected to evolve as information on this species increases and
additional sites are confirmed and defined, the Canadian Oregon Spotted Frog Recovery Team
keeps a working document that is used to formulate/track advice on survival and recovery habitat
(Canadian Oregon Spotted Frog Recovery Team unpubl. report). Thus, the procedure to describe
survival habitat supersedes the geospatial delineation. Where additional Oregon Spotted Frog
populations are discovered or new populations established or re-established, additional areas of
survival habitat will be defined.
7.1.1
Habitat needed for survival and recovery
It is recommended that survival habitat be defined as the habitat that is necessary for the
persistence of the species at occupied sites including any newly discovered locations in the
future. Currently that includes the four known occupied locations: Maintenance Detachment
Aldergrove, Mountain Slough, Marie Slough and Morris Valley. It is recognized that these four
occupied locations alone are insufficient to meet the population and distribution goal for the
species “...to maintain and where feasible expand extant Oregon Spotted Frog populations, and
establish six or more additional self-sustaining populations in B.C.”. Recovery habitat is also
required and can be defined as habitat where the species is reintroduced or translocated
(introduced), in adjacent areas where the species has expanded its range. The habitat necessary
for recovery must also include the habitats found at historical and high-suitability sites needed to
expand the extant populations and to meet the population targets of six more occupied locations
(10 in total) within 10 years. Thus, survival habitat will apply at any occupied sites and
additional identification will be completed for recovery habitat following the same procedure
described below once candidate locations or historical sites are confirmed.
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Recovery Strategy for Oregon Spotted Frog
January 2012
7.1.2
Biophysical attributes of survival and recovery habitat
Oregon Spotted Frogs have three distinct life-seasons within a year: the breeding/oviposition
season, the active summer season, and the overwintering period. Habitat requirements during
each of these life stages differ as described in Section 3.3.1 “Habitat and Biological Needs”.
7.1.3
Procedure to describe survival and recovery habitat
It is recommended that the description of survival/recovery habitat follow a precautionary
approach designed to minimize the chance of loss of Oregon Spotted Frog populations, or
degradation or loss of habitat, based on the current understanding of the biology of the species,
and potential threats to populations and habitat.
The procedure to describe survival/recovery habitat at the four known Oregon Spotted Frog
populations is based on known occurrences for all life stages and the habitat needed to sustain
those life stages. Identification of survival/recovery habitat for Oregon Spotted Frog must be
based on a scientifically defensible mechanism to delineate and rate habitat suitability during
each of the three important life-seasons, and the required area to protect populations and habitat
from potential threats. The procedure outlined below has taken into consideration the habitat
features or attributes that must be maintained or managed for persistence of the species.
Recommended procedure to describe survival/recovery habitat around known Oregon Spotted
Frog populations:
1. Identify locations of all occurrences. Use all occurrence records (including future
records) for all life stages (egg, juveniles, adults, larvae/tadpoles) at (a) the 4 occupied
locations, (b) any new sites, and (c) all re/introduction sites once occupied 1.
2. Define the area of survival/recovery habitat to include occupied (based on the above
occurrence) and suitable aquatic and terrestrial habitat. This includes but is not limited to
contiguous riparian habitat and associated watercourses (e.g. water bodies, wetlands,
ponds, seasonally inundated areas, wetted areas, seeps, streams and ditches, etc) and
essential habitat as identified in section 3.3.1 as well as through the habitat
mapping/modelling for the breeding/oviposition season, the active summer season, and
the overwintering period within a 3000 meter radius of the above occurrence points.
Pearl and Hayes (2004) and Hayes (pers. comm.) found that Oregon Spotted Frogs can move 3
kilometres. Cushman and Pearl 2007 captured an adult female 2799 m (estimated stream
distance) from her original capture location which also suggests 3 km as a maximum distance of
travel. Taking a precautionary approach and protecting large areas of habitat is important to
increase the chance of preserving potential metapopulations (Semlitsch 2002) and to increase the
1
Occupied means any current or historical occurrence, of any life stage (egg, juveniles, adults, larvae/tadpoles) of
Oregon Spotted Frog whether introduced or naturally occurring.
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Recovery Strategy for Oregon Spotted Frog
January 2012
likelihood of including the variety of habitats required by the Oregon Spotted Frog. This
selection should exclude the Fraser River Main stream.
3. Capture suitable connected habitat, by including the entire watercourse that Oregon
Spotted Frogs are known to use as part of the area of survival/recovery habitat. Suitable
habitats and connecting watercourses/water bodies should be included if they are < 260 m
in elevation, and within a 3 km radius of the occurrence records to the extent of the
included watersheds. In addition, isolated patches of suitable habitat within 400 m of the
habitat described above should also be included.
To increase the likelihood of maintaining suitable hydrological characteristics associated with
Oregon Spotted Frog habitat, the entire wetland and associated watercourses should be included
in the area. Watercourses, including streams and ditches, are included because they are important
travel corridors for Oregon Spotted Frogs (Watson et al. 2003, Pearl and Hayes 2004). Oregon
Spotted Frogs also have been reported to use ditches for breeding and over-wintering (Watson et
al. 2003, Pearl and Hayes 2004). Including the entire wetland and associated watercourses will
increase the probability of including habitat important to the species during all its life-seasons
(including winter; there are little data on winter habitat use in B.C.) and across a variety of
environmental conditions (e.g. extremely wet or dry years, or long-term changes potentially
associated with climate change). Additionally, it will avoid inadvertent impacts to sites that may
be occupied or colonized in the future but presently lack sufficient inventory.
The maximum elevation at which habitat was considered suitable for Oregon Spotted Frog was
established as 260 m. Pearl and Hayes (2004) examined the relationship between elevation and
latitude from known sites in B.C., Washington, Oregon and California (N=73), and suggested
that at the northern limit of its range, as in B.C., the Oregon Spotted Frog is unlikely to be
discovered above 200 m elevation. However, to increase the probability of including suitable
habitat, the 200 m limit was increased by 30%.
The maximum distance that Oregon Spotted Frogs were considered able to move across
unsuitable habitat (e.g., without an aquatic connection) to colonize isolated patches of suitable
habitat was established as 400 m. Although most Oregon Spotted Frog movements occur along
aquatic habitat, individuals occasionally move across nonaquatic habitat (e.g., Watson et al.
2003, M. Hayes, pers. comm., 2011). Hayes suggested that 400 m was likely the maximum
distance that Oregon Spotted Frog could move across non-aquatic habitat (M. Hayes, pers.
comm. 2011).
4. Include supporting habitat that is essential to ensure water quantity and quality. This may
include groundwater flow and discharge areas that flow into the above identified sites,
such as intermittent stream channels, springs or water seeps, and contiguous riparian
habitat and connecting watercourses that may be > 250 meters and within 3 km of the
occurrence records to the extent of the included watersheds.
Oviposition and breeding microhabitats are frequently associated with groundwater up-wellings,
which provide relatively stable thermal and water quality conditions. Supporting habitat is an
essential component of survival/recovery habitat for Oregon Spotted Frogs. This step requires a
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Recovery Strategy for Oregon Spotted Frog
January 2012
closer assessment of the local hydrological conditions and an understanding of the essential
hydrological conditions upslope or upstream that must be maintained in order for the occupied
sites to persist.
5. For each of the above selected areas (occupied, connecting, supporting habitats),
delineate a 45 m buffer area on either side of the bank above the high water mark 1 of the
watercourse (or the top of bank for ditches). This is to be applied around all occupied
habitats (procedure 1 and 2), all other suitable habitats in the watershed where it is
feasible for the Oregon Spotted Frog to colonize (procedure 3), all types of groundwater
flow that may influence the water quantity or quality of the above, where the
groundwater flow is identified to its headwaters (procedure 4). For supporting habitat
within intact forested areas (procedure 4), a smaller area of 30 meters either side of the
bank can be implemented instead of 45 meter if the adjacent landscape remains forested.
If the land is converted from forest to any other landuse the original 45 m buffer applies.
This area is essential to buffer the habitat from surrounding landuses. Impermeable surfaces such
as roads do not contribute to the size of the area. Where roads or other impermeable features are
present within the survival/recovery habitat area, the area is increased by the width of the feature.
If currently forested areas are converted to more intensive land uses (e.g. agriculture, urban
development, commercial uses such as gravel removal or others), the survival/recovery habitat
area should be increased to provide a 45 m area around the wetland and associated stream,
ditches, and seeps. To finalize the area of survival/recovery habitat, the wetlands should be
surveyed on the ground to establish the high water mark. The area boundary would then be
measured outward from the high water mark.
The aquatic nature of Oregon spotted frogs makes them vulnerable to chemicals entering wetland
habitat (see threats section). Various research projects have reported that buffer retention can
reduce the input of chemicals into waterways. Lowrance and Sheridan (2005) reported that on a
2.5% slope, a 75 m three-zone buffer (grass, managed forest and unmanaged forest) between an
agricultural field and a stream reduced nitrate-N by 59%, ammonium-N by 48%, and Total N by
37%. Lowrance et al. (1997) reported that a 50 m managed 3-zone buffer (grass, managed pine
forest, and hardwood forest) was effective in removing herbicide residue (atrazine and alachlor)
by the time it reached a stream. Thompson et al. (2004) reported that 30-60 m buffers were
effective in limiting glyphosate concentrations to low levels compared to levels in wetlands with
no buffers.
A meta-analysis of peer-reviewed studies of the effectiveness of riparian buffers in removing
nitrogen by Mayer et al. (2007) suggested that buffers >50 m wide were more effective at
removal of nitrogen than buffers 0-25 m wide. Based on their analysis they reported that to
remove 75% of nitrogen would require a 49 m buffer and to remove 90% would require a 149 m
1
“high water mark” means the visible high water mark of a stream where the presence and action of the water are
so common and usual, and so long continued in all ordinary years, as to mark on the soil of the bed of the stream a
character distinct from that of its banks, in vegetation, as well as in the nature of the soil itself, and includes the
active floodplain. http://www.env.gov.bc.ca/habitat/fish_protection_act/riparian/documents/regulation.pdf assessed
October 2011.
44
Recovery Strategy for Oregon Spotted Frog
January 2012
buffer (categories had large SE). Removal of nitrogen was influenced by buffer width, water
flow (removal from subsurface flow is more efficient than surface flow), and type of vegetation
present. To adopt a precautionary approach, and to increase the probability that the habitat
critical to the survival of the Oregon spotted frog is maintained and buffered from surrounding
land practices, the recommend area of critical habitat in agricultural and urban landscapes is 45
m around wetlands and either side of watercourses adjacent to agricultural/residential habitat,
and 30 m either side of supporting watercourses in forested habitat.
7.2
Specific Human Activities Likely to Damage
Survival/Recovery Habitat
Activities described in Table 5 include those likely to damage survival habitat for Oregon
Spotted Frog. But destructive activities are not limited to those listed. Damage would result if
part of the survival habitat were degraded, either permanently or temporarily, such that it would
not serve its function when used by the species. Damage may result from single or multiple
activities at one point in time or from the cumulative effects of one or more activities over time.
Most of the identified threats to Oregon Spotted Frog populations in Canada are habitat-related,
thus specific threats discussed in Section 4.2 should be assessed at each site and used to
determine if an activity is permitted. Where a situation does not clearly fit in with the activities
identified in Table 5, but has a potential impact on Oregon Spotted Frog habitat, the proponent is
advised to contact the responsible jurisdiction for guidance on the activity.
Table 5. Examples of human activities likely to damage survival/recovery habitat for Oregon Spotted
Frog.
Activity
Description
Hydrological modifications
Spray/application of fertilizers or
chemicals (including manure or
pesticides) to Oregon Spotted
Frog habitat, or the area
immediately adjacent to it
Input of sediment to Oregon
Spotted Frog habitat
Any alteration of watercourses that leads to changes in water quantity
and/or in the flow rate and pattern. This includes but is not limited to
changes in: water levels (excessive drawdown or sudden increases),
ground water (diversion or loss), flow, water quantity (removal or
increases), disturbance (e.g. ditch cleaning), or diversion of water
(ditching or culverting or relocation). Retaining natural water levels is
important for populations of Oregon Spotted Frog, particularly during:
the period between oviposition and hatching of tadpoles; over-winter
during the coldest period; and in areas that are required to support
oviposition, over-wintering, foraging or dispersal. Change in hydrology
may result in direct or indirect mortality, loss of recruitment and
reduced survivorship.
Oregon Spotted Frogs are sensitive to pollutants and are highly aquatic;
thus, activities that cause contaminants to enter the wetland or
watercourse could be damaging. Examples include runoff or spray of
pesticides or fertilizers into or adjacent to Oregon Spotted Frog habitat,
runoff of manure stored adjacent to habitat, or direct input of
manure/urine by cattle or livestock.
Sedimentation can directly affect water quality and modify channel
structure. The build-up of sediment in the watercourse/wetland or the
watercourses that input water/materials to the watercourse/wetland can
lead to large runoff events with a resulting sudden influx of pollutants
from the surrounding area. Forestry activities, where they include
harvesting close to watercourses draining into wetlands, can increase
45
Recovery Strategy for Oregon Spotted Frog
January 2012
Removal or alteration of natural
riparian vegetation around
watercourses or wetlands
Introduction of exotic predators
Mining
sedimentation. In addition, cattle access to watercourses or wetlands
can affect bank stability and result in increased sedimentation. Lack of
rooted vegetation along the banks of watercourses affects bank
stability; this may result from activities such as cattle access,
machinery, or herbicide application.
Removal or alteration of natural riparian vegetation around
watercourses or wetlands can alter the functioning of the ecosystem.
Examples of activities that can disturb natural vegetation include
encroachment during or as a result of development or adjacent land use,
and forestry activities. Alteration of the natural environment can also
be caused by the introduction of exotic species, such as reed
canarygrass, which can build up and modify the structure of the
environment.
Introduction of exotic predators and competitors, such as the Bullfrog
or Green Frog, can also have a negative impact on the quality of habitat
for Oregon Spotted Frog habitat and increased potential for disease
introduction.
Mining exposes rock mineral leachate at a higher rate than normal, and
the resulting run-off can pollute adjacent habitat. Mining may also
alter subsurface water flow, and lead to landslides.
8 PERFORMANCE MEASURES
Evaluation criteria will be developed as the recovery team refines the recovery objectives for the
Oregon Spotted Frog. Based on current information, criteria used to evaluate progress towards
meeting the recovery goal include:
Objective 1
• Occupied locations monitored yearly using spring egg mass counts and capture-markrecapture of adults and juveniles (ongoing monitoring continuing to at least 2020)
• Stable or increase numbers at each extant population (based on egg mass counts ongoing monitoring continuing to at least 2020)
• Number of occupied sites increased by 6 by 2021
• Threats mitigated and impacted areas restored at the four occupied locations by 2020
• Refined survival and recovery habitat polygons (ongoing) and no further habitat
loss/degradation within those areas, evaluated in 2020
• Improved water quality at impacted sites through site repair and restoration and stable or
improving water quality at all sites, evaluated annually continuing to at least 2020
• At least 5 landowners engaged in stewardship actions by 2015 with numbers of engaged
citizens increasing through time continuing to at least 2020)
Objective 2
• Habitat assessment at each occupied location to assess major threats and barriers to
population growth at that location by 2014
• Intervention protocol (to ensure no reproductive loss caused by controllable desiccation
or through acute threats) developed and implemented by 2012 with no reproductive loss
46
Recovery Strategy for Oregon Spotted Frog
January 2012
•
•
(for example, the protocol will outline when, where and how stranded eggs will be
relocated or brought in; continuing to 2020)
At a least two priority sites, restoration techniques implemented (e.g., such as reed canary
grass control to improve the quality of oviposition sites or habitat expansion) by 2013
(adaptive management will be ongoing to 2020)
An assessment of captive rearing/population augmentation efforts to date completed by
2014 and draft protocol for a cost-effective captive rearing program completed by 2014
Objective 3
• The number of occupied locations increased from 4 to at minimum 10 locations
(including the 4 extant) with a minimum number of breeding adults 1 at each location to
sustain a viable population by 2020
• Total population size increased to approximately 2000 or more breeding individuals 2 by
2020
• Husbandry facilities capable of rearing up to 3000 animals at 2 or more institutions by
2020
• Assurance populations at 2 or more institutions by 2015
Objective 4
• All suitable wetlands within the range of the Oregon Spotted Frog surveyed (initial
surveys to be completed by 2014)
Objective 5
• Monitoring of captive-reared and released frogs post-release to estimate survival
(ongoing spring and fall surveys continuing to 2020)
• Monitoring of newly introduced frog populations for breeding (ongoing spring surveys
continuing to 2020)
• Monitoring of augmented populations for signs of increased breeding activity (increasing
trend in number of egg masses) (ongoing spring surveys continuing to 2020)
• Radio-telemetry and habitat assessment conducted at restored sites to assess if Oregon
Spotted Frog microhabitat needs have been met by restoration efforts by 2014. An
adaptive recovery implementation plan has been prepared using the information above by
2015.
• Oregon Spotted Frog populations monitored using spring egg surveys and capture-markrecapture studies to assess effectiveness of whether threat mitigation measures (e.g.,
removal of introduced species and improvement in water quality) ongoing and continuing
to at least 2020
1
Targets for the numbers of breeding adults will vary by site. The recovery team anticipates establishing a minimum
population size of 200 breeding adults at each site though carrying capacity may limit achievable number.
2
Total population size is enumerated using an estimate of breeding individuals. Minimum population sizes will be
re-evaluated once a demographic sensitivity analysis is complete, and sizes may vary according to the estimated
carrying capacity of each site.
47
Recovery Strategy for Oregon Spotted Frog
January 2012
Objective 6
• Radio-telemetry studies conducted at occupied locations to better understand Oregon
Spotted Frog microhabitat use and threats/risks at seasonal habitats initiated/completed
by 2014 and continuing to 2015
• Capture-mark-recapture data gathered at currently extant and future reintroduced
populations to construct population matrix models (potential graduate student projects
continuing up to 2020)
• Focused research on threat/risk factors that might be constraining recovery of populations
(e.g., such as genetic bottlenecking, disease epidemiology, invasive predation pressure,
and habitat modification due to invasive species) initiated and ongoing projects as needed
• Research on threat mitigation and restoration techniques completed by 2016. This
information used to update best management protocols or guidance documents for habitat
measures (e.g., ditch cleaning, the establishment of riparian buffers, or habitat
enhancement for co-occurring endangered species such as the Salish Sucker) by 2020 and
ongoing as needed
• A well-designed monitoring program in place so that potential effects of climate change
can be detected early enough to make mitigation and intervention possible (ongoing
continuing to 2020)
9 EFFECTS ON OTHER SPECIES
It is unlikely that recovery activities will have any adverse effects on other species at risk.
Habitat enhancement and restoration projects that benefit the Oregon Spotted Frog will likely
positively benefit other threatened species and species of special concern, such as the Red-legged
Frog, American Bittern, Great Blue Heron, Green Heron, the Salish Sucker (Catostomus
catostomus), and the Pacific Water Shrew (Sorex bendirii).
In addition, efforts to enhance and restore wetland function and the habitats occupied by the
Oregon Spotted Frog will likely have a positive effect on aquatic plant, invertebrate, and
vertebrate populations that occupy or visit the affected wetlands.
48
Recovery Strategy for Oregon Spotted Frog
January 2012
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reintroduction sites at Campbell Valley Regional Park, Langley, BC. Greater Vancouver
Regional District, Parks Department.
Haycock, R.D. 2000. Status update and management plan for the Oregon Spotted Frog (Rana
pretiosa) at Maintenance Detachment Aldergrove. Director General Environment,
National Defence Headquarters, Ottawa, ON.
Hayes, M.P. 1994a. Current status of the Spotted Frog (Rana pretiosa) in western Oregon.
Unpubl. rep. for Oregon Department of Fish Wildlife, Portland, OR.
Hayes, M.P. 1994b. The Spotted Frog (Rana pretiosa) in western Oregon. Final report to the
Oregon Department of Fish and Wildlife, Portland, OR.
Hayes, M.P. 1997. Status of the Oregon Spotted Frog (Rana pretiosa sensu stricto) in the
Deschutes Basin and selected other systems in Oregon and northeastern California with a
rangewide synopsis of the species’ status. Final report prepared for The Nature
Conservancy under contract to the U.S. Fish and Wildlife Service, Portland, OR.
Hayes, T.B., A. Collins, M. Lee, M. Mendoza, N. Noriega, A.A. Stuart, and A. Vonk. 2002.
Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low
ecologically relevant doses. Proc. Natl. Acad. Sci. 99:5476–5480.
Hayes, M.P., J.D. Engler, R.D. Haycock, D.H. Knopp, W.P. Leonard, K.R. McAllister, and L.L.
Todd. 1997. Status of the Oregon Spotted Frog (Rana pretiosa) across its geographic
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Oregon Chapter of The Wildlife Society, Aug. 15, 1997, Corvallis, OR.
Hayes, M.P., J.D. Engler, S. Van Leuven, D.C. Friesz, T. Quinn, and D.J. Pierce. 2001.
Overwintering of the Oregon Spotted Frog (Rana pretiosa) at Conboy National Wildlife
Refuge, Klickitat County, Washington 2000–2001. Final report to the Washington
Department of Transportation. Washington Department of Fish and Wildlife, Olympia,
WA. 86 pp. Cited in Pearl and Hayes (2004).
Hayes, M.P., C.J. Rombough, C.B. Hayes, and J.D. Engler. 2005. Rana pretiosa (Oregon
Spotted Frog) predation. Herpetol. Rev. 36:307.
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Hecnar, S.J. 1995. Acute and chronic toxicity of ammonium nitrate fertilizer to amphibians from
southern Ontario. Environ. Toxicol. Chem. 14:2131–2137.
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selection of Oregon Spotted Frogs (Rana pretiosa). J. Herpetol. 37:292–300.
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Personal Communications
Dr. Christine Bishop, Conservation Scientist, Environment Canada, Science and Technology
Branch, Delta, BC.
Purnima Govindarajulu, Small mammal and Herpetofauna Specialist, B.C. Ministry of
Envirnoment, Victoria, BC.
Russ Haycock, Hyla Environmental Services Ltd., Vancouver, BC.
Marc P. Hayes, Portland State University, Portland, OR.
Denis Knopp, B.C.’s Wild Heritage, Chilliwack, BC.
Sylvia Letay, Ecosystems Officer, B.C. Ministry of Envirnoment, Surrey, BC.
Monica M. Pearson, Consultant, Balance Ecological Environmental Consulting, Vancouver, BC.
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Kym Welstead, Senior Ecosystems Biologist, B.C. Ministry of Environment, Surrey, BC.
Bob Woods, National Defence Headquarters, Ottawa, ON.
52
Recovery Strategy for Oregon Spotted Frog
January 2012
Appendix 1. Population estimates at occupied sites in British
Columbia
Table A1. Population estimates at four currently occupied locations in British Columbia, based on egg
mass counts. Note that sampling intensity does vary across years.
Number of
Population
Total number of
Estimated number
communal
Year
egg masses
of breeding adults
oviposition sites
Maintenance Detachment Aldergrove a
1997
90
2000
29
2001
31
2002
34
2003b
2004
2005
2006
2007
2008
2009
2010
Mountain Slough
1997
2000
2001c
2002c
2003
2004
2005
2006
2007
2008
2009
2010
Maria Slough e
1997
2000
2001
2002
2003f
2004
2005
2006
2007
2008
2009
2010
Morris Valley
2008
4
6
6
7
180
58
62
68
12
10
7
8
0
0
0
0
5
4
4
6
0
0
0
0
24
20
14
16
0
0
1 adult male observed
0
16
43
70
96
54
62
49
NAd
37
50
45
52
2
4
12
7
5
6
8
NAd
NAd
5
8
13
32
86
140
192
108
124
98
NAd
74
100
90
104
38
75
71
144
127
117
125
99
21
67
45
67
3
3
10
7
6
5
4
NAd
NAd
10
10
NAd
76
150
142
288
254
234
250
198
42
134
90
134
77
15
154
53
Recovery Strategy for Oregon Spotted Frog
January 2012
Population
Year
2009
2010
All Four Sites
1997
2000
2001
2002
2003
2004
2005
2006g
2007 g
2008h
2009 hi
2010h
Average
Number of
Total number of
Estimated number
communal
egg masses
of breeding adults
oviposition sites
63
39
5
7
126
78
144
147
172
274
193
189
181
107
58
194
153
158
164
9
13
28
21
15
15
15
6
NAd
30
23
20g
17
288
294
344
548
386
378
362
214
116
388
306
316
328
a
Release of metamorphic Oregon Spotted Frogs back into Maintenance Detachment
Aldergrove (year and number): 2005 (317) and 2006 (423).
b
Includes a count of one pair observed in amplexus. Egg mass not located.
c
Incomplete survey due to lack of permission to access private properties.
d
Data not available.
e
Release of metamorphic Oregon Spotted Frogs back into Maria Slough (year and number):
2002 (354); 2003 (381); 2004 (836); 2007 (846); and 2008 (1012).
f
Assume female frogs lay one annual clutch of eggs, and a 1:1 sex ratio.
g
Data not available from at least 1 site, so numbers are minimums.
h
Totals include data from the new (fourth) population (Morris Valley) discovered in 2008.
i
One site with multiple single egg masses that had moved due to water fluctuations.
54
Recovery Strategy for Oregon Spotted Frog
January 2012
Appendix 2. Site-specific threat assessment
Table A2. Threats to Oregon Spotted Frog populations in B.C. by occupied site (expanded from Hayes
1997).
Threats/Limiting factor
1. Habitat losses caused by
human activities
2. Hydrological alteration
3. Habitat losses caused by
natural succession
4. Insufficient habitat size
5. Exotic predatorse
6. Exotic, invasive vegetationf
7. Genetic isolation due to habitat
fragmentation (distance in km to
nearest occupied site)
8. Risk of drought and climate
change
9. Water quality
10. Disease
11. Low population
numbers/small populations
Site a
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
MDA
MTS
MS
MO
Relative
impacts b
C
C
C
P
C
P
P
C
P
C
C
C
N (18 ha)
N (20 ha)
N (16 ha)
N
P (Bf)
C (Gf)
C (Bf, Gf)
U
P
P
P
N
C
C
C
C
C
C
C
C
U
C
C
U
U
U
U
U
P
C
C
P
Spatial/temporal
nature c
W-C
W-H
L-H
W-C
W-C
W-H
W-H
W-H
W-C
W-C
W-C
W-C
W-E
W-E
W-E
W-E
W-C
W-C
W-C
L
W-C
W-C
W-C
L
W (50)
W (7)
W (8)
W (7)
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-C
W-H
L-H
W-C
Certainty d
C
C
C
C
P
C
C
C
C
C
C
P
P
P
P
P
C
P
P
C
C
C
C
C
P
P
P
P
C
P
P
P
S
C
C
S
C
S
S
S
C
C
C
C
a
Site: MDA = Maintenance Detachment Aldergrove; MTS = Mountain Slough; MS = Maria Slough; MO = Morris.
Relative Impact: P = Predominant; C = Contributing; U = Unknown; N = None.
Spatial/Temporal Nature: W = Widespread; L = Localized; C = Chronic; E = Episodic; H = Historical.
d
Certainty: C = confirmed based on empirical data; P = Probable; S = Speculative.
e
Exotic Predators: Bf = Bullfrog; Gf = Green Frog.
f
Exotic, Invasive Vegetation: reed canary grass.
b
c
55
Recovery Strategy for the Oregon Spotted Frog
January 2012
Appendix 3. Maps of survival habitat for Oregon Spotted Frog in B.C.
Figure A 1. Area of survival habitat (yellow shadow) for Oregon Spotted Frog around Morris Valley, B.C.
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Recovery Strategy for the Oregon Spotted Frog
January 2012
Figure A 2. Area of survival habitat (yellow shadow) for Oregon Spotted Frog around the wetland at Maria Slough, B.C.
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Recovery Strategy for the Oregon Spotted Frog
January 2012
Figure A 3. Area of survival habitat (yellow shadow) for Oregon Spotted Frog around Mountain Slough, B.C.
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Recovery Strategy for the Oregon Spotted Frog
January 2012
Figure A 4. Area of survival habitat (yellow shadow) for Oregon Spotted Frog around the wetland at Maintenance Detachment
Aldergrove, B.C.
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