Conservation Agreement for the Oregon Spotted Frog
(Raila pretiosa) in the Klamath Basin of Oregon
U.S. Fish and Wildlife Service
Fremont-Winema National Forests
Lakeview District of the Bureau of Land Management
Medford District of the Bureau of Land Management
Klamath Marsh National Wildlife Refuge
I. SPECIES ADDRESSED
Rana pretiosa (Oregon spotted frog)
II. INVOLVED PARTIES
U.S. Fish and Wildlife Service
Laurie Sada, Field Supervisor
Klamath Falls Fish and Wildlife Office
1936 California Avenue
Klamath Falls, OR 97601
(541) 885-8481
Attn: Trisha Roninger
USDA Forest Service
J. Richard (Rick) Newton, Acting Forest Supervisor
Fremont-Winema National Forests
1301 S. G Street
Lakeview, OR 97630
(541) 947-6256
Attn: Amy Markus
Bureau of Land Management
Carol Benkosky, District Manager
Lakeview District
2795 Anderson Avenue, Bldg. #25
Klamath Falls, OR 97603
(541) 883-6916
Attn: Rob Roninger
Bureau of Land Management
Tim Reuwsaat, District Manager
Medford District
3040 Biddle Road
Medford, OR 97504
(541) 618-2200
Attn: Steve Godwin
Klamath Marsh National Wildlife Refuge
Ron Cole, Project Leader
Klamath Basin National Wildlife Refuge Complex
4009 Hill Road
Tulelake, CA 96134
(541) 783-3380 Klamath Marsh Refuge Office
(530) 667-2231 Klamath Complex Office Tulelake
Attn: Faye Weekley
1
III. AUTHORITY, PURPOSE, OBJECTIVES, AND GOALS
A. Authority
The authority to enter into this voluntary Conservation Agreement derives from the
Endangered Species Act (Act) of 1973, as amended; the Fish and Wildlife Act of 1956, as
amended; and the Fish and Wildlife Coordination Act of 1934, as amended.
B. Purpose
The purpose of this Conservation Agreement is to fonnally document the intent of the parties
involved to protect and contribute to the conservation of the Oregon spotted frog by
implementing conservation actions for the species and its habitat on federal lands in the
Klamath Basin of Oregon. This Conservation Agreement is not a decision document or
fonnal direction for the federal agencies. Rather, it is intended to guide strategic planning,
project development, management, conservation actions, and research studies for Oregon
spotted frog in the Klamath Basin.
C. Goals and Objectives
The goal of this agreement is to provide a means for the protection and conservation of the
Oregon spotted frog in the Klamath Basin of Oregon. This agreement is not intended to
provide site specific infonnation, but rather to include broad-scale infonnation, goals, and
conservation actions for Oregon spotted frog conservation in the Klamath Basin.
The objectives of this agreement are to: I) manage occupied habitat in a manner that sustains
and/or restores its ability to support Oregon spotted frog populations; 2) stabilize or increase
populations within the Klamath Basin; 3) reduce threats; and 4) increase distribution among
available suitable habitats by restoring or creating habitat.
IV. INTRODUCTION
This agreement includes a brief summary and overview of the Oregon spotted frog, including
a species description, and a description ofthe Oregon spotted frog's habitat, life history,
distribution, status, as well as threats facing the species range-wide and in the Klamath Basin.
This includes both information based on available credible research and the professional
opinion of federal wildlife biologists. This information may need to be updated as new
science becomes available. For more detailed infonnation regarding Oregon spotted frog,
refer to the Conservation Assessment for the Oregon spotted frog (Rona pretiosa) (Cushman
and Pearl 2007), which is incorporated by reference.
For federal Oregon Bureau of Land Management (BLM) lands in Oregon, the Special Status
Species policy details the need to manage for species conservation. Conservation is defined
as the use of all methods and procedures which are necessary to improve the condition of
Special Status Species and their habitats to a point where their Special Status recognition is
no longer warranted. In addition, implementation of the policy is intended to ensure that
actions funded, authorized, or carried out by the BLM do not contribute to the need to list
species under the Endangered Species Act.
2
For the Pacific Northwest Region ofthe USDA Forest Service, the Sensitive Species policy
requires the Agency to maintain viable populations of all native and desired non-native
wildlife, fish, and plant species in habitats distributed throughout their geographic range on
national forest system lands. Management should also preclude a trend towards federal
listing, for any identified Sensitive Species.
For the U. S. Fish and Wildlife Service (USFWS), the Endangered Species Act (Section
4(b)(1)(A)) provides an avenue for the U. S. Fish and Wildlife Service to enter into voluntary
agreements that benefit species which are under evaluation for listing under the Act. These
agreements are intended to further the purposes of the Act by supporting actions that may
improve the status of an individual species and which may preclude the need to list the
species.
V. STATUS AND DISTRIBUTION OF SPECIES
A. Species Description
The Oregon spotted frog is the most aquatic ranid frog in western North America (Leonard et
al. 1993). The back usually has black spots or rings with uneven edges and light centers
(Leonard et al. 1993, Corkran and Thoms 1996). The belly and groin region display a
mottled wash of red to orange in adults, but coloration in juveniles can be absent or occur
over small portions of underside of thighs or groin (Hayes 1998). The eyes are upturned
relative to other Northwestern native frogs, and the feet can be fully webbed (Corkran and
Thoms 1996). Hind legs are relatively short compared to body length. Eggs are laid in fistsized spherical masses containing 300 to 1500 embryos. Tadpoles are brown or gray with
gold flecks, and the tail is about twice the body length (Leonard et al. 1993, Corkran and
Thoms 1996).
B. Habitat Description
Oviposition sites tend to be close to shore in shallow water, and are usually positioned above
vegetated, gently-sloped substrates (Pearl et al. 2009) Eggs are generally laid above sedges,
grasses, and rushes in early spring before plant growth has begun (Pearl et al. 2009). Postbreeding habitats used by Oregon spotted frogs are typically aquatic, and often have areas of
floating, emergent or submergent vegetation that is near refuge that can be used to escape
predators. One study in Oregon found that egg mass numbers were positively related to the
presence of other Oregon spotted frog breeding sites nearby and the amount of emergent and
subemergent vegetation coverage (Pearl et aI. 2009). Habitats used during winter include
flowing channels and springs (Shovlain 2005, Chelgren et al. 2008).
Based on a telemetry study at one lowland site in western Washington, Watson et al. (2003)
summarized seasonal requirements for Oregon spotted frogs as: 1) stable, shallow water for
egg and tadpole survival in the breeding season; 2) deep, moderately vegetated pools for
adult and juvenile survival in the dry season; and 3) shallow water levels over emergent
vegetation for protecting all age classes dming the cold weather in the wet season.
3
C. Life History
Oregon spotted frogs typically oviposit communally and these aggregations can contain eggs
from 100 or more females in larger populations (Pearl et al. 2009). Communal oviposition
may be linked to the female's affinity for depositing egg masses on top of previously laid egg
masses (Licht 1969). Licht (1969) reported that initial breeding activity from one low
elevation site in British Columbia began when air temperatures were at least 5° Celsius
(4 I°Fahrenheit). However, the trigger for breeding is not well understood and is likely to
vary geographically and with elevation (c. Pearl, pers. comm).
High breeding site fidelity is suspected because oviposition often occurs within 0.5 m (20 in)
of previous years locations (Licht 1969). Use of traditional oviposition sites that may have
limited availability because of unique characteristics, and the possibility that adults may have
limited flexibility to switch sites, makes the Oregon spotted frog particularly vulnerable to
habitat changes at oviposition sites (Hayes 1994).
Several aspects of the Oregon spotted frog's life history have been proposed as contributing
to the species' vulnerability to habitat alterations (Hayes 1994, 1997, Watson et al. 2003,
Pearl et al. 2004, Cushman and Pearl 2007, Pearl et al. 2009): 1) communal egg laying at
sites used year after year restricts the number of reproductive sites; 2) the species' warm
water requirement results in habitat overlap with introduced warm water fish; 3) the active
season warm water requirement may limit suitable habitat in the cool climates of the Pacific
Northwest; 4) the species may be vulnerable to the potential loss or alteration of springs used
for overwintering; and 5) changes that increase deep, permanent water components are likely
to favor establishment of non-native bullfrogs and fish, both of which may be detrimental to
Oregon spotted frogs.
D. Distribution
The species is currently known from less than 50 population complexes in southwestern
British Columbia, western and south-central Washington, and western, central, and southcentral Oregon; no populations are known to persist in California (Cushman and Pearl 2007).
Revisits of historic localities led Hayes (1997) to conclude that the species may be lost from
70 to 90% of its historic range.
Most of the extant sites in the Klamath Basin are relatively higher in elevation and maintain
the least altered hydrology (Hayes 1997). These sites also have the fewest exotic aquatic
predators when compared to historic sites (Hayes 1997). In general, habitat modifications
and aquatic predators have been more substantial at lower elevations than higher elevations,
suggesting that either one or a combination may be responsible for the failure to record the
species at lowland historical sites (Hayes 1997).
E. Status
The Oregon spotted frog is considered a Candidate species by the U.S. Fish and Wildlife
Service. Candidate species are plants or animals for which the USFWS has sufficient
information on their biological status and threats to propose them as endangered or
threatened under the Endangered Species Act but for which. development of a proposed
listing regulation is precluded by other higher priority listing activities.
4
The Oregon spotted frog is ranked as Sensitive-Critical by Oregon Department of Fish and
Wildlife; a Special Status Species by Oregon BLM; and Sensitive by the Pacific Northwest
Regional Forester's Special Status Species List. The Oregon Natural Heritage Information
Center gives the Oregon spotted frog a Global rank ofG2 (globally imperiled because of
rarity); a National rank as N2 (taxa that are threatened with extirpation or presumed to be
extirpated in the United States); a State rank ofS2 (taxa that are threatened with extirpation
or presumed to be extirpated from the state of Oregon). The Oregon Natural Heritage
Information Center also classifies the Oregon spotted frog on List I which means the species
is threatened with extinction or presumed to be extinct throughout their entire range; these
are the taxa most at risk, and should be the highest priority for conservation action.
VI. THREATS FACING THE SPECIES: RANGE-WIDE AND KLAMATH BASIN
The information below provides an overview of threats to the species both range-wide and
within the Klamath Basin. Much of the literature cited below on Oregon spotted frogs
derives from British Columbia, Washington, and Deschutes Basin in Oregon. Genetic data
suggest that the Klamath Basin populations form a group that differs from population
segments in other portion of the species range (Blouin 2000). Absent information comparing
the Klamath genetic unit to other population segments, caution should be exercised when
extrapolating information from other areas to Klamath Basin populations.
In general, there is little information on the prevalence and magnitude of threats to Oregon
spotted frogs in the Klamath Basin. More importantly, the relative importance of each
stressor and the potential for interaction amount multiple stressors is not well understood.
One study recognized evidence that Oregon spotted frog populations in the Klamath Basin
may be at greater risk than those in the upper Deschutes basin: I) surveys in 2006 found
fewer egg masses in the Klamath breeding ponds; 2) there are greater distances and more
modified lands between known sites in the Klamath; and 3) among the sites that have more
than 5 years of monitoring data, the only one with a clear declining trend is in the Klamath
Basin (Jack Creek) (Pearl et aI. 2009).
A. Loss and Alteration of Wetland Habitat
Range-wide
Twenty-one of twenty-eight Oregon spotted frog sites (75%) assessed in the mid-1990's have
some human-related hydrological alterations (Hayes 1997, Pearl 1999). Noted modifications
ranged from minor (e.g. local ditching around springs) to substantial changes, including
major modifications of historic flow patterns (Hayes 1997, Pearl 1999) resulting in loss of
wetland habitat. Hydrologic changes have also resulted in a reduction in the natural
disturbance regimes that historically created habitat for Oregon spotted frog such as fluvial
cutting and meanders of streams and rivers and the creation of ponds and open water
conditions by beaver. Studies also suggest that wetland loss and modification may provide
conditions that favor non-native exotic fish and bullfrogs (Adams 1999, Maret et aI. 2006,
Adams and Pearl 2007).
5
Fluctuating water levels at critical periods in the Oregon spotted frog's life cycle, whether
natural or human-induced, may negatively affect the species. Due to the tendency for
communal oviposition, water level reduction during the 2-3 week window when eggs are
developing can result in the loss of significant portions of that year's reproductive effort.
Reduction in water levels may expose larval and post-metamorphic Oregon spotted frogs to
predation as a result of reducing cover and confining the frogs to smaller areas. Large
increases in current or water level can be detrimental for egg masses if they become
submerged or drift to unfavorable locations (Garwood et al. 2008).
Klamath Basin
Extensive wetland draining, mainly for agricultural purposes, has occurred in the Klamath
Basin starting in the late 1800's and continuing through the 1970's. The hydrology of the
Upper Klamath and Agency Lakes, as well as other areas in the Klamath Basin, have been
significantly changed by extensive diking and draining of seasonal wetlands, by water
diversions from tributaries, by diverting water out of the lakes, and by the construction of a
dam at the lakes outlet in 1921 that allowed the lake to be operated as a storage reservoir
(DEQ 2002).
Akins (1970) did the first comprehensive analysis of the basin's wetlands. He estimated
there were originally 350,000 acres (1,400 km 2) of wetlands in the upper basin, that private
farming modified 50,000 acres (200 km 2), and that another 200,000 acres (800 km2) were
affected by drainage within the Klamath Project. The Klamath Project was developed by the
Bureau of Reclamation in the early part of the 20 th century (Foster 2002). Largely based on
the analysis by Atkins, other authors reported estimates of wetlands losses in the upper basin
of 65 to 90 percent (e.g., Bottorff 1989; Gearhart et al. 1995; NRCS 2006).
Hydrologic modifications at occupied Oregon spotted frog locations in the Klamath Basin
range from minor changes to major modification of historic flow patterns. In addition, the
diversion of water for agricultural purposes can result in an annual variation of water levels
that can negatively impact Oregon spotted frog, particularly during the larval and postmetamorphic life stages.
Wetlands losses in the basin have slowed and there are numerous restoration activities
occurring throughout the Klamath Basin. For example, the Natural Resources Conservation
Service reported that as of 2007, 8,900 acres of wetlands were restored for fish and wildlife
habitat and 21,000 acres enrolled into the Wetlands Reserve Program (NRCS 2007). In
addition, the proposed Klamath Basin Restoration Agreement may lead to additional
rehabilitation efforts and partnership opportunities to benefit watershed function and aquatic
ecosystems throughout the Klamath Basin.
B. Plant Succession and Other Vegetative Changes
Range-wide
Succession by native and non-native vegetation has the potential to modify conditions at
wetlands associated with Oregon spotted frog habitat (Cushman and Pearl 2007). Threats
6
.
exist from exotic plant invasions, such as reed canarygrass (Phalaris arundinacea).
Aggressive exotics can completely alter the structure of wetland environments and can create
dense areas of vegetation that may be unsuitable as Oregon spotted frog habitat (McAllister
and Leonard 1997).
Succession (changes in plant communities) may be a factor threatening many Oregon spotted
frog sites. Fire, beaver, and active floodplain meanders were natural disturbances that were
historically more common within Oregon spotted frog habitat, and acted to periodically
create open water habitat (Cushman and Pearl 2007).
Klamath Basin
At some locations occupied by Oregon spotted frog (e.g. Klamath Marsh), the lack of
disturbance to vegetation is resulting in a transition of open water habitat to solid stands of
bulrush, cattail, or sedge (C. Damberg pers. com 2008). Fire, grazing, and haying operations
that historically occurred in these areas on a more frequent basis are no longer causing the
necessary disturbance to set back plant succession (C. Damberg pers. com. 2008). In some
cases, grazing or haying for biological reasons may benefit Oregon spotted frog habitat by
opening the vegetation (C. Damberg pers. com 2008). Historically, it is expected that beaver
played an important role in managing vegetation and creating open water conditions and
ponds in the Klamath Basin.
Lodgepole pines and other tree and shrub species are encroaching on wetland habitats
occupied by spotted frogs at several sites in the Klamath Basin. It is suspected that lodgepole
encroachment adjacent to known breeding habitat could result in shading ofthe water (A.
Markus pers. obs. 2009). The effects of this are not well understood, and merit more
attention. Local vegetation changes, in particular the increase of woody vegetation such as
lodgepole pine or willow, have the potential to affect frog habitat by altering base flows,
isolation, evaporation and transpiration, or patterns of snow and ice accumulation or thaw.
C. Interactions with Non-native Fishes and American Bullfrogs
Range-wide
There are a number of documented and potential predators of Oregon spotted frogs. Several
introduced fish, as well as American bullfrogs (Rana catesbeiana [=Lithobates
catesbeianus]), have been transplanted into the Oregon spotted frogs' historic range and may
have contributed to the decline of this and other native frogs around the western USA (Hayes
and Jennings 1986, Kiesecker and Blaustein 1998, Pilliod and Peterson 2001, Pearl et al.
2004, Vredenberg 2004).
Bullfrogs have been introduced into the Pacific Northwest from eastern North America.
Bullfrogs are thought to possess several ecological advantages over northwestern ranid frogs:
1) post-metamorphic bullfrogs can attain much larger body sizes (and thus eat larger food
items) than Oregon spotted frogs in most habitats in the Pacific Northwest (Pearl et al. 2004);
2) bullfrogs do well and may even benefit from introduced fish that present a direct threat to
native northwestern ranids, in part because bullfrog tadpoles are not palatable to many ofthe
eastern fish that have been introduced in the west (Kruse and Francis 1977, Adams et al.
7
2003); 3) larval bullfrogs overwinter at least once and reach sizes exceeding spotted frogs
(and most other western native frogs); bullfrog tadpoles can physically displace native
tadpoles from shallows that are wanner and offer refuge from fish predators (Kiesecker and
Blaustein 1998); and 4) bullfrog tadpoles are more resistant to the effects of pesticides and
heavy metals than other ranid frogs (Hayes and Jennings 1986).
Data also exist to suggest facilitative interactions between habitat modifications that increase
permanence and exotic fish and bullfrogs (Adams 1999, Maret et al. 2006, Adams and Pearl
2007). Thus, these issues should not be treated independently. For example, non-native fish
can influence bullfrog tadpole survival by preying upon one of their primary predators,
dragonfly nymphs (Adams et al. 2003). This relationship implies that reducing the
distribution and abundance of non-native fish has the potential to reduce survival of bullfrog
tadpoles (Adams et al. 2003).
The widespread introduction of non-native fish has affected many amphibians native to lentic
habitats of western North America (Adams 1999, Pilliod and Peterson 200 I, Pearl et al.
2005, Vredenberg 2004). Oregon spotted frogs, which are palatable to fish, did not evolve
with these introduced species and may not have the mechanisms to avoid fish that prey on the
tadpoles of native amphibians. In a study that assessed the broad status of the species and
potential influences of habitat and stressors on population size, the number of egg masses at a
pond was negatively associated with non-native fish access to potential overwintering habitat
(Pearl et aI., 2009). Brook trout are the most frequently recorded introduced predator at a
subset of Oregon spotted frog sites in Oregon (Hayes 1997). Oregon spotted frog can persist
at some sites with introduced fish, however the mechanisms that allow coexistence are not
understood.
Klamath Basin
Exotic aquatic predators are widespread in the Klamath Basin and occur at or in close
proximity to most of the sites occupied by Oregon spotted frogs. Some of the non-native
species in the Klamath Basin include brook trout, brown trout, brown bullhead, fathead
minnow, sunfish, largemouth bass, crappie, and bullfrogs. The Jack Creek and Parsnip Lakes
sites represent the only Oregon spotted frog populations in the Klamath Basin that currently
lack exotic aquatic predators.
D. Livestock Grazing
Range-wide
Despite a pronounced interest in the question, data on the impacts of grazing on Oregon
spotted frogs are sparse. Several factors are likely to contribute to whether grazing has
negative and/or positive local impacts on the species and its habitat. These factors include,
but are not limited to the intensity of grazing, the timing of grazing relative to vulnerable life
stages of Oregon spotted frog, and habitat type and extent.
Grazing effects are likely to be complex and vary among sites and seasons. However, the
tendency for multiple life stages of Oregon spotted frog to use shallow edge habitats among
emergent vegetation, and for livestock to use similar areas for grazing and watering, suggest
8
"
there is potential for negative impacts from grazing. Because of this potential to have Oregon
spotted frog life stages and livestock concentrated in the same areas and habitats, particularly
in low water conditions, there are likely to be risks to Oregon spotted frogs associated with
heavy livestock use: direct trampling of vulnerable life stages such as metamorphic and
young juvenile frogs; reduced water quality (e.g., increased nitrogenous waste, and possible
introduction of pathogens or hormones); and reduced or altered vegetation cover (important
to spotted frog life stages as refugia from predators). Cause and effect information is lacking
for all of these factors (Cushman and Pearl 2007), and further research is warranted to
determine the magnitude of these potential impacts.
Experimental work is warranted to better understand whether specific levels and timing of
grazing can be used to maintain or improve habitat conditions for Oregon spotted frog in
sites where vegetation succession is a concern (Watson et al. 2003, Cuslunan and Pearl
2007). Assessments of the potential negative grazing effects, and a closer examination of
management that will minimize those effects while helping to maintain open habitat, will
assist in the development of grazing prescriptions where Oregon spotted frog conservation is
a priority (Cushman and Pearl 2007). An adaptive management approach to grazing offers
the potential to maintain desired habitat conditions, by separating livestock grazing from
vulnerable life stages of Oregon spotted frog (Cushman and Pearl 2007).
Studies have been conducted on the relationships between livestock grazing and the Oregon
spotted frogs' close relative, the Columbia spotted frog (Rana luteiventris). It is important to
recognize that the responses of Colwnbia spotted frog to grazing should not be extrapolated
to Oregon spotted frog because the two species differ in demography, habitat use, and their
capacity to move terrestrially (Licht 1975). Bull and Hayes (2000) did not detect differences
in the number of egg masses or of recently metamorphosed Columbia spotted frogs in grazed
and ungrazed sites. In addition, a study by Adams et al. (2009) found that despite significant
effects of grazing on vegetation height, there was no evidence that full or partial grazing
exclosures affected Columbia spotted frog egg mass counts, larval survival, or metamorphic
size in the first two or three years after fence installation.
Klamath Basin
Grazing may pose a greater risk in the Klamath Basin than in other parts of the Oregon
spotted frog range because the negative impacts may be more severe in low water years.
Livestock grazing is occurring in most of the populations in the Klamath Basin, and the
timing and intensity of grazing is variable. The specific impacts from grazing in the Klamath
Basin are largely unknown and warrant further investigation into the potential impacts.
In 2005, a graduate student from Oregon State University completed her master's thesis on
the impacts oflivestock grazing on habitat use by adult Oregon spotted frogs by monitoring
frog locations in grazed and ungrazed treatments on Jack Creek (Shovlain 2005). Based on
the proportion oftime frogs spent inside exclosures, there was evidence that as grazing
pressure increased, frogs preferred ungrazed livestock exclosures. Although the frogs
responded to grazing, this study could not detennine if grazing has either a positive or
negative impact on the frogs (Shovlain 2005).
9
E. Water Quality Degradation
Range-wide
Water quality and the absorption of contaminants in water through the skin and gills in
immature forms may threaten this species (Marco et a1. 1999). Acidification of water, as
reflected by low pH can inhibit fertilization and embryonic development in amphibians,
reduce their growth and survival through physiological alterations, and produce
developmental anomalies (Hayes and Jennings 1986, Boyer and Grue 1995). Research
conducted by McKibbin et a1. (2008) suggests that water quality did correlate significantly
with the embryonic survivorship of Oregon spotted frog population at two study sites in
British Columbia, Canada.
A low pH may enhance the effects of other factors, such as mobilization of heavy metals
from sediments. Pesticides, herbicides, heavy metals, nitrates and nitrites, and other
contaminants introduced into the aquatic environment are known to negatively affect various
life stages of a wide range of amphibian species, including ranid frogs (Hayes and Jennings
1986, Boyer and Grue 1995). When nitrogen in the form of ammonia is introduced into
water, the ammonia may "consume" dissolved oxygen as nitrifying bacteria convert the
ammonia into nitrite and nitrate (DEQ 2002). Marco et al. (1999) found that Oregon spotted
frog are very susceptible to chronic doses of nitrate and nitrite.
Klamath Basin
Water quality data at occupied Oregon spotted frog sites in the Klamath Basin are limited.
Most of the available information discussed below applies to the entire Klamath Basin,
including the Upper Klamath Basin in Oregon and the Lower Klamath Basin in California,
and is not meant to imply that these conditions exist at known Oregon spotted frog locations.
Additional investigation and monitoring of water quality and its effects on Klamath Basin
Oregon spotted frog populations is warranted and important for conservation of this species.
Historical changes in land and water usage have impacted nutrient cycling dynamics in much
of the Klamath Basin (DEQ 2002). In the Upper Klamath Lake and Agency Lakes, total
phosphorus is identified as a pollutant that causes elevated pH, reductions in dissolved
oxygen, and increases in chlorophyll-a, often pushing the lakes into an exaggerated state of
eutrophication (DEQ 2002). Although historical accounts indicate that Upper Klamath Lake
and Agency Lakes would have been considered eutrophic even 100 years ago, many
locations have observed total phosphorous concentrations elevated significantly above these
background levels contributed from agricultural and other nonpoint sources (DEQ 2002).
Waters at the Klamath Basin National Wildlife Refuges have high temperatures, elevated pH,
.
and low dissolved oxygen (Sorenson and Schwarzbach 1991), which singly or in
combinations could have detrimental effect on the developing embryos offrogs (Boyer and
Grue 1995). Water at the Klamath Basin National Wildlife Refuges contained ammonia
(NH3) levels above those levels reported to have no-observed-effect concentration for
leopard frog tadpoles (Boyer and Grue 2008). In addition, a study conducted in 1988-1989
detected five different organochlorine pesticides in bottom sediment (Sorenson and
Schwarzbach 1991).
10
F. Isolation and Ownership
Range-wide
For a highly aquatic species such as the Oregon spotted frog, which breeds in specific
wetland types and exists in a landscape often substantially altered from historic conditions,
factors relating to isolation include: 1) distance between sites; 2) permeability of habitat
between source site and nearest breeding site; 3) frequency of dispersal movements; and 4)
risks to Oregon spotted frogs moving between potential breeding sites (e.g., exotic predators,
culverts, etc.) (Cushman and Pearl 2007). With the exception ofthe upper Deschutes Basin
sites, distances separating most of the known Oregon spotted frog populations are generally
at least 2 kilometers (km) (1.2 miles (mi)) from one another (Cushman and Pearl 2007).
Long distance movements by Oregon spotted frog appear to be infrequent and strongly
linked to aquatic corridors (Watson et al. 2003).
A recent genetic analysis by Funk et al. (2008) found low levels of within population genetic
variation in Oregon spotted frogs. Low genetic variation may be attributed to small effective
population sizes, historic or current genetic bottlenecks, and/or low levels of within
population genetic variation (Funk et al. 2008).
Klamath Basin
The straight line distance between Oregon spotted frog populations range from 2.41 to 24.1
km (1.5 to IS miles) in the Klamath Basin. In the case ofJack Creek, the distance is very
long (approximately IS miles) to its nearest known adjacent population (Williamson River,
Klamath Marsh National Wildlife Refuge), and in many years it is connected with surface
water for only very brief periods during snow melt.
More than 34% of the Klamath Basin is in private ownership (DEQ 2002), and it is suspected
there are undiscovered Oregon spotted frog populations on private lands. Most of the known
populations of Oregon spotted frog in the Klamath Basin are found in mixed ownerships
including both federal and private lands. In some cases, this mixed ownership may provide
challenges for conservation and restoration.
G. Climate Change
Range-wide
Climate change is generally predicted to result in increased air and water temperatures,
decreased water quality, increased evaporation rates, increased proportion of precipitation as
rain instead of snow, earlier and shorter runoff seasons, and increased variability in
precipitation patterns (Adams and Peck 2002). Winter snow pack accumulations are
expected to be reduced due to wanner winter and spring temperatures, winter snowline will
shift to higher elevations, and snow will melt earlier in the spring (Mote et al. 2003). Snow
pack in the Washington Cascades is predicted to decrease by 44% by 2020 and by 58% by
2040 as compared to current conditions (Lawler and Mathias 2007). Less snow pack,
especially at lower elevations, will likely result in lower summer water flow and increased
summer water temperatures.
II
Localized drought can negatively impact Oregon spotted frogs in all life cycles, particularly
in isolated populations occupying fragmented habitat. Seasonal drought affects populations
by increasing the likelihood of egg mass desiccation and exposure to freezing; concentrating
post-metamorphs, thus elevating predation risk; and increasing the impacts oflocalized
events (Licht 1974, 1975; Kiesecker and Blaustein 1997). Multiple year droughts carry
impacts similar to seasonal droughts, but may expose populations to negative long term
impacts including decreased population numbers, potential losses in population
heterozygosity, exacerbation of impacts from catastrophic events, and potential extirpation
(which is more serious in isolated populations and metapopulations with remote chances of
being recolonized).
Changes in water levels due to climate change or localized drought can cause seasonal loss of
habitat and degradation of essential shoreline vegetation. Hayes (1997) assessed 38 percent
of Oregon spotted frog sites as having a moderate to high risk from drought (i.e. the potential
for a drop in water level that could reduce or eliminate the species' habitat). Locations
expected to have the greatest risk from drought are those dependent upon on surface flow
rather than flows from springs. Sites with the greatest risk from drought are in Oregon in the
Klamath and Deschutes Basins (Hayes 1997).
Klamath Basin
Recent reports have examined climatologic and hydrologic information for Klamath Marsh
and the Upper Klamath Basin. Mayer et a1. (2007) found that, similar to Klamath Marsh,
inflows and tributary flows at Upper Klamath Lake show a long-term declining trend. The
declines are particularly notable when examining the late summer/fall base flow period of the
year. The results indicate that there has been a statistically significant decline in late season
net inflows to the lake over the 1961 to 2007 period (Mayer 2008). Climate change is likely
to affect sites differently in the Klamath Basin based on the water source. The effects of
climate change are expected to be more evident in systems that are dependent on snow melt
such as Jack Creek and less evident in systems that are dependent on ground water such as
Crane Creek and Wood River.
In general, the water supply in the Klamath Basin is expected to become more variable. Dry
years or periods with wide variation in the water supply have become more common. As a
result, is it expected that the magnitude of stressors to Oregon spotted frog will increase as
they interact with water supply. For example, stressors such as grazing, bullfrog and fish
predation, and habitat loss to succession and plant invasions may become more acute risks in
dry years. In recent years, low water conditions have resulted in the desiccation of egg
masses and stranding of tadpoles at Jack Creek.
H. Diseases
Range-wide
Disease can strongly impact small populations that are already stressed by other factors (e.g.
drought or low food availability). Amphibians are known to be affected by a variety of
diseases (Berger et a1. 1998). There is little information on the specific effects of disease and
parasitism on Oregon spotted frogs. Oomycete fungi (including Saprolegnia sp; Petrisko et
12
al. 2008) and the chytrid fungus (Batrachochytrium dendrobatatidis; Pearl et al. 2009) have
been found on Oregon spotted frog life stages, but their effects at the population scale are
poorly known. BatrachochytriunI dendrobatatidis in particular, merits further attention,
since it has impacted amphibian populations in other regions ofthe world.
Klamath Basin
A study conducted by Pearl et al. (2009), detected BatrachochytriunI dendrobatatidis (Bd) in
all of the 36 Oregon spotted frog sites sampled, including five sites located in the Klamath
Basin. This study detected one of the highest rates of Bd prevalence (68.1 % of juveniles and
adults) and occupancy (100% of surveyed sites), but found low prevalence of Bd in larvae
(2.8%) (Pearl et al. 2009). The paucity of data on ccological effects of chytrid fungus makes
it impossible to assess the threat it may present to Klamath populations.
VIII. CONSERVATION ACTIONS TO BE UNDERTAKEN
The Fremont-Winema National Forests, Lakeview District ofthe Bureau of Land
Management, Medford District of the Bureau of Land Management, and Klamath Marsh
National Wildlife Refuge agree to work locally and cooperatively to:
I) Develop Oregon Spotted Frog Site Management Plans for each spotted frog population on
federal lands within the Klamath Basin. The Plans may include recommendations of site
specific management actions, and the desired timeline for each conservation action. By
2012, each site will have a plan completed.
2) By 2011, identify and prioritize research needs for the conservation of the species in the
Klamath Basin. This includes estimating the funding and personnel needs to carry out such
research needs.
3) By 2011, evaluate connectivity concerns between sites in the Klamath Basin. Identify
feasible improvements for connectivity between sites, determine appropriate management
actions through restoration, and include these actions along with funding requests in Site
Management Plans.
4) Where feasible, work to restore or enhance ephemeral and permanent wetlands within and
adjacent to occupied Oregon spotted frog sites. Identify these ephemeral and permanent
wetlands, determine the appropriate management needed for restoration, and include these
actions along with funding requests in Site Management Plans.
5) Work to restore and maintain open water in occupied Oregon spotted frog habitat and
provide early seral vegetation communities in close proximity to occupied Oregon spotted
frog habitat sites. Identify areas that lack open water conditions, determine appropriate
management actions, and include these actions along with funding requests in Site
Management Plans.
6) Where grazing on Federal lands occurs in occupied Oregon spotted frog habitat, then develop
a comprehensive grazing strategy using adaptive management principles through a
collaborative process. This process should include interdisciplinary discussion and reviews
from federal wildlife biologists, range conservationists, and other specialists as needed, as
well as the perspectives of the permittee and/or private landowner, and the USFWS. The
final decision as to which strategy to adopt remains with the appropriate federal line officer.
13
7) Evaluate whether local fish stocking practices may be adversely affecting Oregon spotted
frog populations and propose adjustments if needed. Site Management Plans will assess
whether non-native fish are present at the Oregon spotted frog sites, what the potential
negative effect of their presence may be, and propose adjustments if needed.
8) Develop cooperative Oregon spotted frog restoration projects with our partners and pursue
outside funding for project implementation. Cooperatively work with our partners on
developing grant proposals to leverage funding.
9) Coordinate and prioritize surveys an on annual basis to monitor Oregon spotted frog
populations and describe habitat conditions. Participate in range-wide monitoring strategies.
Pursue funding for monitoring of Oregon spotted frog restoration projects.
10) On an annual basis, provide all existing Oregon spotted frog survey and habitat data to the
USFWS to enter into a universal data base.
II) Continue to participate in the Regional Interagency Special Status Species (ISSSP) Oregon
Spotted Frog Working Group to identify priorities and information needs.
12) On an annual basis, enter all data into NRlS Wildlife, GeoBOB, or ORNHIC.
13) In cooperation with the USFWS, work collaboratively with private landowners to manage,
restore, and monitor populations on private lands located near or adjacent to federal lands
and that have known or suspected Oregon spotted frog habitat.
14) Increase awareness of Oregon Spotted frog management and conservation needs through
public outreach and education.
IS) In support of adaptive management, a review of this conservation agreement and each
individual Site Management Plan will be conducted every five years to update with new
scientific findings or habitat infonnation.
The Klamath Falls Fish and Wildlife Office of the U.S. Fish and Wildlife Service agrees to
work locally and cooperatively to:
I. Assist the Forest, Districts, and Refuge in managing Oregon spotted frog populations and
habitats within the Klamath Basin, and to protect their significant biological and ecological
values consistent with current law, regulations, policies, and existing management plans.
2. Review monitoring data and conservation activities in cooperation with the Forest, Districts,
and Refuge and recommend changes in the status of the Oregon spotted frog as appropriate.
3. Meet annually or as needed with Forest, Districts, and Refuge to discuss Oregon spotted frog
status and management needs.
4. Share all new information on the Oregon spotted frog with the Forest, Districts, and Refuge.
5. Assist with the development and review of Site Management Plans.
6. Continue to participate in the Regional Interagency Special Status Species (ISSSP) Oregon
Spotted Frog Working Group to identify priorities and information needs.
7. Support implementation and monitoring of actions that conserve and protect the species by
providing funding if possible, helping to search out potential funding sources, and assisting
with grant writing as appropriate.
8. By 2012, develop an Interagency Klamath Basin Oregon Spotted Frog Action Plan and
prioritize potential restoration projects across the various spotted frog populations in the
basin. This plan will be updated annually as new Site Management Plans are created, new
information is gathered, and new restoration actions are proposed.
14
9. Work collaboratively with private landowners to manage, restore, and monitor populations
on adjacent private lands which have known or suspected Oregon spotted frog habitat.
10. Provide financial and technical support for monitoring, research, and education efforts where
feasible.
11. Compile all existing Oregon spotted frog survey and habitat data into a universal database.
12. Increase awareness of Oregon Spotted frog management and conservation needs through
public outreach and education.
13. In support of adaptive management, a review ofthis conservation agreement and each
individual site management plan will be conducted every five years to update with new
scientific findings or habitat infonnation.
IX. FUNDING AND IMPLEMENTATION OF CONSERVATION MEASURES
This Conservation Agreement is subject to available funding and staffing. This does not impose
financial obligations on any of the federal agencies signing this agreement. The parties to this
agreement are committed to seeking funding to implement this conservation agreement each
year.
X. DURATION OF AGREEMENT
The duration of this Conservation Agreement is for 10 years following the date of the last
signature. The parties involved will review the Conservation Agreement and its effectiveness
every 5 years to detennine whether it should be revised. During the last month in which it is
valid, the Conservation Agreement must be reviewed and either modified, renewed, or
tenninated. If some portion of this Agreement cannot be carried out or if cancellation is desired,
the party requesting such action will noti fy the other parties within one month of the changed
circumstances.
15
XI. SIGNATURES
;20/0
2-(17/1
0
J. Rich
I' (Rick) Newton, Acting Forest Supervisor
Fremont-Winema National Forests
US. Forest Service
Dute
Carol BelJkosky, District Mana er
Lakeview District
Bureau ofLand Management
Date
Tim Reuwsaat, District Manager
Medford District
Bureau ofLand Management
Ron Cole, Project Leader
Klamath Basin National Wildlife Refuges
US. Fish and Wildlife Service
Date
16
VI. BIBLIOGRAPHY AND PERSONAL COMMUNICATION
Adams, M. J. 1999. Correlated Factors in Amphibian Decline: Exotic Species and Habitat
Change in Western Washington. Journal of Wildlife Management 63:1162-1171.
Adams, MJ., C.A. Pearl, B. McCreary, S.K. Galvan, SJ. Wessell, W.H. Wente, C.W. Anderson,
and A.B. Kuehl. 2009. Short-term effect of cattle exclosures on Columbia spotted frog (Rana
luteiventris) populations and habitat in northeastern Oregon. Journal of Herpetology. 43: 132138.
Adams, MJ., C.A. Pearl, and R.B. Bury. 2003. Indirect facilitation of an anuran invasion by nonnative fishes. Ecology Letters 6:343-351.
Adams, MJ. and C.A. Pearl. 2007. Problems and opportunities managing invasive bullfrogs- Is
there any hope? Chapter 38 In Gherardi, F., ed., Biological Invaders in Inland Waters: Profiles,
Distribution, and Threats: The Netherlands, Springer, p. 679-693.
Adams, R.E. and D.E.Peck. 2002. Climate change and drought: Implications for the West.
Western Economic Forum. 1:14-19.
Akins, G. J. 1970. The effects ofland use and land management on the wetlands of the Upper
Klamath Basin. M.S. Thesis. Western Washington College, Bellingham, WA, USA.
Berger, 1., R. Speare, P. Daszak, D.E. Green, A.A. Cunningham, C.L. Goggin, R. Slocombe,
M.A. Ragan, A.D. Hyatt, K.R. McDonald, H.B. Hines, K.R. Lips, G. Marantelli, and H. Parkes.
1998. Chytridiomycosis causes amphibian mortality associated with population declines in the
rainforests of Australia and Central America. Proc. Natl. Acad. Sci., USA 95:9031-9036.
Blouin, M. 2000. Final report for Challenge Cost Share Agreement No. 06-20-99-021, Analysis
of population genetic structure in the Oregon spotted frog, Rana pretiosa. Oregon State
University, Corvallis, Oregon.
Bottorff, J. 1989. Concept plan for waterfowl habitat protection. Klamath Basin, Oregon and
California. U.S Fish and Wildlife Service Region I.
Boyer, R. and C.E. Grue. 1995. The need for water quality criteria for frogs. Environmental
Health Perspectives 103:352-357.
Bull, E.L. and M.P. Hayes. 2000. Livestock effects on reproduction of the Columbia spotted
frog. Journal of Range Management 53:291-294.
Chelgren, N.D., C.A. Pearl, M.J. Adams, and J. Bowerman. 2008. Demography and movement
in a relocated population of Oregon spotted frogs (Rana pretiosa): Influence of season and
gender. Copeia2008:742-751.
17
Corkran, C.C. and C. Thoms. 1996. Amphibians of Oregon, Washington and British Columbia:
A field identification guide. Lone Pine Publishing Co, Inc. Redmond, Washington. 176 pp.
Cushman, K.A. and C.A. Pearl. 2007. A Conservation Assessment for the Oregon Spotted Frog
(Rana pretiosa). USDA Forest Service Region 6 and USDl Bureau of Land Management,
Oregon and Washington.
Damberg, Carol. 2008. Personal communication.
DEQ. 2002. Upper Klamath Lake Drainage Total Maximum Daily Load (TMDL) and Water
Quality Management Plan (WQMP). State of Oregon Department of Environmental Quality.
http://www.deg.state.or.us/wg/tmd lsi docs/kIamathbasin/ukldrainage/tmdlwgmp.pdf
Foster, D. 2002. Refuges and reclamation. Conflicts in the Klamath Basin, 1904-1964. Oregon
Historical Quarterly 103(2): 150-187.
Funk, W.C., C.A. Pearl, H.M. Draheim, MJ. Adams, T.D. Mullins, and S.H Haig. 2008.
Range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana
pretiosa) in Northwestern North America. Molecular Phylogenetics and Evolution 49:198-210.
Garwood J. M., C. A. Wheeler, R. M. Bourque, M. D. Larson, and H. H. Welsh, Jr. 2007. Egg
mass drift increases vulnerability during early development of Cascades frog (Rana cascadae).
Northwestern Naturalist, 88:95-97.
Gearhart, R.A., J.F. Anderson, M.G. Forbes, M. Osburn, D. Oros. 1995. Watershed strategies
for improving water quality in Upper Klamath Lake, OR. Humbolt State University.
Hayes, M. P. 1994. The spotted frog (Rana pretiosa) in western Oregon. Final report to the
Oregon Department of Fish and Wildlife. 31 pp. + Appendices.
Hayes, M.P. 1997. Status ofthe 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 repOit prepared for The Nature Conservancy
under contract to US Fish and Wildlife Service, Portland, Oregon. 57 pp + Appendices.
Hayes, M.P. 1998. The Jack Creek population of the Oregon spotted frog (Rana pretiosa)
Chemult Ranger District, Winema National Forest (Klamath County, Oregon). Final report
prepared for The Nature Conservancy under contract to the Winema National Forest.
Unpublished Report 14 pp.
Hayes, M.P. and M.R. Jennings. 1986. Decline ofranid frog species in Western North America:
are bullfrogs (Rana catesbeiana) responsible? Journal of Herpetology 20:490-509.
Kiesecker, J. M. and A. R. Blaustein. 1997. Population differences in responses of red-legged
frogs (Rana aurora) to introduced bullfi·ogs. Ecology 78:1752-1760.
18
Kiesecker, J. M. and A. R. Blaustein. 1998. Effects of introduced bullfrogs and smallmouth bass
on microhabitat use, growth, and survival of native red-legged frogs (Rana aurora).
Conservation Biology 12:776-787.
Kruse, K.C. and M.G. Francis. 1977. A predation deterrent in the larvae of the bullfrog, Rana
catesbeiana. Transactions ofthe American Fisheries Society. 106:248-252.
Lawler, J.J. and M. Mathias. 2007. Climate Change and the Future of Biodiversity in
Washington. Report prepared for the Washington Biodiversity Council.
http://www.biodiversity.wa. govI documents/WA-CC-report-final.pdf
Leonard, W.P., H.A. Brown, L.L.c. Jones, K.R. McAllister, and R.M. Storm. 1993. Amphibians
of Washington and Oregon. Seattle Audubon Society, The Trailside Series. Seattle, Washington.
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. 1974. Survival of embryos, tadpoles, and adults of the frogs Rana aurora aurora and
Rana pretiosa pretiosa sympatric in southwestern British Columbia. Canadian Journal of
Zoology 52:613-627.
Licht, L.E. 1975. Comparative life history features of the western spotted frog, Rana pretiosa,
from low-and high-elevation populations. Canadian Journal of Zoology 53:1254-1257.
Marco, A., C. Quilchano, and A.R. Blaustein. 1999. Sensitivity to nitrate and nitrite in pond
breeding amphibians from the Pacific Northwest, USA. Environmental Toxicology and
Chemistry 18:2836-2839.
Maret, T.J., J.D. Snyder, and J.P. Collins. 2006. Altered drying regime controls distribution of
endangered salamanders and introduces predators. Biological Conservation 127: 129-138.
Markus, A.L. 2009. Personal observation.
Mayer, T., F.Wurster, and D. Craver. 2007. Klamath Marsh Hydrology and Water Rights.
Unpublished Report, U.S. Fish and Wildlife Service, Dept of Interior. Portland, OR.
Mayer, T.D. 2008. Analysis of trends and changes in Upper Klamath Lake hydroclimatology.
Unpublished report. U.S. Fish and Wildlife Service. Portland, OR.
McAllister, K.R. and W.P. Leonard. 1997. Washington State status report for the Oregon Spotted
Frog. Washington Department ofFish and Wildlife, Olympia, 38 pp.
McKibbin, R., Dushenko, W. T., vanAggelen, G. & Bishop, C. A. 2008. The influence of water
quality on the embryonic survivorship of the Oregon spotted frog (Rana pretiosa) in British
Columbia, Canada. Science ofthe Total Environment: 395; 28-40.
19
Mote, P. W., E. Parson, A. F. Hamlet, W. S. Keeton, D. Lettenmaier, N. Mantua, E. L. Miles, D.
Peterson, D. L. Peterson, R. Slaughter, and A. K. Snover. 2003. Preparing for climatic change:
The water, salmon, and forests ofthe Pacific Northwest. Climatic Change 61(1-2):45-88.
http://www.springerlink.com!contentlt20l899l71134th3/fulltext.pdf
NRCS. 2006. Conservation resource brief Klamath River Basin. Natural Resources
Conservation Service. http://www.nrcs.usda.gov/feature/outlooklKlamath2.pdf
NRCS. 2007. Klamath Basin conservation partnership accomplishments. Natural Resources
Conservation Service.
http://www.nrcs.usda.gov/featurelklamathlimages/BrochureProgressReport2008.pdf
Pearl, c.A. 2010. Personal communication.
Pearl, C.A. 1999. The Oregon spotted frog (Rana pretiosa) in the Three Sisters Wilderness
ArealWillamette National Forest: 1998 Summary of Findings. Unpubl. Report to US Fish and
Wildlife Service, Portland, Oregon. 23 pp.
Pearl, C.A., MJ. Adams, and N. Leuthold. 2009. Breeding habitat and local population size of
the Oregon spotted frog (Rana pretiosa) in Oregon, USA. Northwestern Naturalist 90: 136-147.
Pearl, C.A., MJ. Adams, R. B. Bury, and B. McCreary. 2004. Asymmetrical effects of
introduced bullfrogs (Rana catesbeiana) on native ranid frogs in Oregon. Copeia 2004:11-20.
Pearl, C.A., J. Bowerman, and D. Knight. 2005. Feeding behavior and aquatic habitat use by
Oregon spotted frogs (Rana pretiosa) in central Oregon. Northwestern Naturalist 86:36-38.
Pearl, C. A., J. Bowernlan, M.J. Adams, and .D. Chelgren. 2009. Widespread Occurrence of
the Chytrid Fungus Batrachochytrium dendrobatidis on Oregon spotted frogs (Rana pretiosa).
EcoHealth. DOl: 10. 1007/s1 0393-009-0237-x.
Petrisko, J.E., C.A. Pearl, D.S. Pilliod, P.P. Sheridan, C.F. Williams, C.R. Peterson, and R.B.
Bury. 2008. Saprolegniaceae identified on amphibian eggs throughout the Pacific Northwest,
USA, by internal transcribed spacer sequences and phylogenetic analysis. Mycologia 100: 17 1180.
Pilliod, D. S. and C. R. Peterson. 2001. Local and landscape effects of introduced trout on
amphibians in historically fishless watersheds. Ecosystems 4:322-333.
Reaser, J. K. 2000. Demographic analysis ofthe Columbia spotted frog (Rana luteiventris): case
study in spatiotemporal variation. Can. J. Zoology 78:1158-1167.
Shovlain, A. 2005. Oregon Spotted Frog habitat use and Herbage (or Biomass) Removal from
Grazing at Jack Creek, Klamath County, Oregon. Master's Thesis, Oregon State University,
Corvallis, Oregon.
20
"
Sorenson, S.K. and S.E. Schwarzbach SE. ] 991. Reconnaissance investigation of water quality,
bottom sediment, and biota associated with irrigation drainage in the Klamath Basin, California
and Oregon, 1988-89. Water-resources investigations report 90-4203. Sacramento, California:
U.S. Geological Survey.
Vredenburg, V. T. 2004. Reversing introduced species effects: Experimental removal of
introduced fish leads to rapid recovery of a declining frog. Proc. Nat. Acad. Sci. 101 :7646-7650.
Watson, J. W., K.R. McAllister, and OJ. Pierce. 2003. Home ranges, movements, and habitat
selection of Oregon spotted frog (Rana pretiosa). Journal of Herpetology 37 (2):292-300.
21