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Movement, Habitat Use, and Dispersal of Juvenile
Oregon Spotted Frogs (Rana pretiosa)
on Joint Base Lewis McChord
by
John Richardson
A Thesis: Essay of Distinction
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
June 2011
©2011 by John Richardson. All rights reserved.
This Thesis for the Master of Environmental Study Degree
by
John Richardson
has been approved for
The Evergreen State College
by
________________________
Judith Bayard Cushing Ph.D.
Member of the Faculty
________________________
Date
ABSTRACT
Movement, Habitat Use, and Dispersal of Juvenile Oregon Spotted Frogs (Rana pretiosa) on
Joint Base Lewis McChord
John Richardson
The dispersal, habitat use and movements of juvenile R. pretiosa on Joint Base Lewis McChord
(JBLM) were monitored using radio telemetry (telemetry). Telemetry occurred in four sessions.
In the first fall 2008 session, six frogs were tracked for 11 to 25 days (x̄=16.66) from 22
September to 17 October. In the second session ten frogs were tracked for 14 to 25 days
(x̄=22.7) from 14 November to 9 December. In spring 2009 12 frogs were tracked from 4 April to
17 June for 9 to 70 days (x̄= 35.25). In fall 2009 12 frogs were tracked for 13 to 34 days
(x̄=23.33) from 29 October to 2 December. Movement of juvenile frogs was influenced by
habitat conditions. Aquatic connectivity during the spring allowed for frogs to make larger
moves. Average daily distance traveled was greater in the spring than the fall (F=16.38
p=.0001). In the fall, average daily distance was not significantly different between tracking
sessions despite frogs from 2009 weighing four times as much as those in 2008 and reaching
near adult sizes. Further, frogs on JBLM used terrestrial habitats at a higher rate (36.5% of the
time) than previously reported. Finally, terrestrial habitat use was higher during the fall (47% in
2008 and 42.45% in 2009) compared to the spring (10.9%). Increased terrestrial use is likely the
result of behavior differences between adult and juvenile R. pretiosa.
Secondary objectives of this study were to improve on telemetry transmitter attachment
techniques for ranid frogs and examine the impacts of frequent handling associated with
telemetry on frog movements. Results suggest that 7mm silk ribbon had the greatest reduction
in injury rates and allowed frogs to break free of transmitters if the frogs could not be
recovered and the transmitters removed by the investigator. Impacts of handling include the
observation that frogs moved further following capture (p=.0067); this increased movement
may have influenced data on habitat use and dispersal.
ii
Contents
List of Figures………………………………………………………………………………………………………………........................... vi
List of Tables………………………………………………………………………………………………………………………………………….vii
Acknowledgments……………………………………………………………………………………………………………………..………….viii
Introduction .................................................................................................................................................. 1
Background ................................................................................................................................................... 4
Global Amphibian Decline......................................................................................................................... 4
Decline of Oregon Spotted Frogs.............................................................................................................. 7
Conservation Status .................................................................................................................................. 9
Current Conservation Actions:................................................................................................................ 10
Geographical Distribution ....................................................................................................................... 12
Taxonomy and Genetics.......................................................................................................................... 14
Species Description ................................................................................................................................. 15
Natural History........................................................................................................................................ 19
Study Area:.............................................................................................................................................. 22
Telemetry ................................................................................................................................................ 23
Methods:..................................................................................................................................................... 24
Statistical analysis ................................................................................................................................... 25
Telemetry ................................................................................................................................................ 25
Movement............................................................................................................................................... 28
Habitat Use ............................................................................................................................................. 29
Transmitter attachment materials.......................................................................................................... 30
Affects of capture on frog movement .................................................................................................... 31
Results and Discussion ................................................................................................................................ 32
Habitat Use ............................................................................................................................................. 32
Fall 2008.............................................................................................................................................. 34
Spring 2009 ......................................................................................................................................... 36
Fall 2009.............................................................................................................................................. 36
Movement............................................................................................................................................... 40
iv
Dispersal.................................................................................................................................................. 43
Affects of capture on frog movement .................................................................................................... 45
Telemetry Attachment Material ............................................................................................................. 46
Conclusion and Future Research Needs ..................................................................................................... 49
Appendix A Definitions of Habitat Categories ............................................................................................ 53
Appendix B: Dispersal of Frogs during telemetry. ...................................................................................... 54
Literature Cited. .......................................................................................................................................... 58
Personal Communications .......................................................................................................................... 62
v
List of Figures
Figure 1: Major causes of global amphibian decline and the number of species affected by each
cause. Threatened species are represented by the red portion of the graph. Source
IUCN http://www.iucnredlist.org/initiatives/amphibians/analysis/major‐threats.......... 7
Figure 2: Historic and Current Distribution of R. pretiosa. Data are from Cushman and Pearl
2007, and McAllister and Leonard 1997............................................................................. 1
Figure 3: Dorsal view of R. pretiosa. Note the presence of a telemetry attachment belt around
the hips. .............................................................................................................................. 1
Figure 4: Ventral view of R. pretiosa: Photo by Gary Nafis. Source:
http://www.californiaherps.com/frogs/pages/r.pretiosa.html ......................................... 1
Figure 5: Comparison of groin patch for R. pretiosa and R. aurora. R. pretiosa is on the right:
Source Washington Herp Atlas Photo by D. Hagin ............................................................. 1
Figure 6: Radio telemetry study area on JBLM. Releases of R. pretiosa for telemetry occurred at
Dailman Lake....................................................................................................................... 1
Figure 7: 28 week BD‐2N radio telemetry transmitter attached to a juvenile Oregon spotted frog
(R. pretiosa)......................................................................................................................... 1
Figure 9: Locations of Frog 335 during fall 2009 telemetry. Note the clustering of points around
a mud puddle in the lower part of the map. ...................................................................... 1
Figure 10: Locations for frog 337 during the spring of 2009. Frog 337 moved the furthest
distance away from the release point of any frog tracked during this study. ................... 1
vi
List of Tables
Table 1: Number of observations and % use of 15 habitats recorded during radio telemetry. *
indicates those habitat categories not used during all three tracking
sessions…………………………………………………………………………………………………………..……………33
Table 2: Terrestrial habitat use recorded during radio telemetry. Habitats without measurable
standing water were considered to be terrestrial with the exception of
muck…………………………………………………………………………………………………………………..………..34
Table 3: Summary of daily distance traveled by frogs during radio telemetry. * Distances
traveled immediately following release were excluded from analysis of maximum
distance traveled. Numbers in red are statistically
significant………………………………………………………………………………………………..…………………..42
vii
Acknowledgments
I would like to thank the following people for their assistance. Without their help I would not
have been able to complete this thesis.
Jim Lynch
Nick Miller
Tiffany Hicks
Lisa Hallock
Marc Hayes
Carri LeRoy
Judy Cushing
viii
Introduction
Historically, the Oregon spotted frog (Rana pretiosa) inhabited shallow warm
water wetlands from northern California to southern British Columbia and was widely
distributed throughout much of the lowlands of the Puget Trough and Willamette
Valley. Over the last 150 years, declines in quantity and quality of habitat have led to
the loss of R. pretiosa from 78% to 90% of its historic range (McAllister and Leonard
1997). Populations of R. pretiosa at the edges of its range and those that inhabited the
lower elevations, such as the Puget Trough and Willamette Valley, have been most
heavily impacted (Pearl and Hayes 2004). R. pretiosa have been extirpated from the
Willamette Valley as well as Northern California and only one population remains in the
Puget Trough (Pearl and Hayes 2004; McAllister and Leonard 1997). Range‐wide
declines have led to legal protections for R. pretiosa under federal, state and provincial
law. R. pretiosa is listed as an endangered species in the state of Washington and is a
candidate for listing under the federal Endangered Species Act (ESA). Canada, Oregon
and California also provide legal protections to R. pretiosa under their respective
endangered species laws.
Compliance with legal protections and the concern over the future viability of R.
pretiosa populations have led to an increase in research into the ecology and habitat use
of R. pretiosa over the last 15 years. Despite this increase in research, much is still
unknown about the ecology of R. pretiosa. Much of what is known about the ecology
and habitat use of R. pretiosa comes from studies conducted in British Columbia during
the seventies and eighties (Lict 1974; Lict 1986a; Lict 1986b). More recent studies have
1
been conducted on the habitat selection and movements of R. pretiosa in Oregon and
Washington, however these studies are focused on adult behavior and habitat needs
(Watson et al 2003; White 2002; McAllister et al 2004). The focus on adult R. pretiosa
has left a gap in the knowledge of juvenile behavior and habitat needs that limit
recovery. Increasing our understanding of the habitat requirements and behavior of
sub‐adult R. pretiosa is important for shaping future recovery of the species. By further
understanding the needs of juvenile R. pretiosa, management strategies can be shaped
to benefit all life stages and therefore have a more positive impact on recovery.
Recovery efforts in the state of Washington have primarily focused on the
protection of existing populations through restoration of oviposition sites. Restoration
projects have focused on removing invasive vegetation such as reed canary grass
(Phalaris arundinacea) and establishing consistent water levels during breeding to
prevent stranding of egg masses. More recent efforts have focused on the
establishment of new populations of R. pretiosa within its historic range. In 2007
Washington created an Oregon spotted frog recovery team consisting of state, federal,
and private organizations to help establish and reach recovery goals. In 2008, the
recovery team started a captive rearing and reintroduction program in order to
establish new populations of R. pretiosa. In October of 2008, the first of five planned
releases of captive reared R. pretiosa occurred at Dailman Lake on Joint Base Lewis
McChord (JBLM). Monitoring of released frogs was begun as part of the reintroduction
program. In 2008 and 2009, radio telemetry (telemetry) was used to monitor dispersal,
2
movements, and habitat use of juvenile R. pretiosa. Transmitter attachment methods
and the impact of frequent handling of frogs were also studied.
Telemetry was selected for monitoring frogs post‐release because it offered
numerous advantages to other monitoring techniques, such as visual encounter surveys
or the use of passive integrated transponders (PIT tags). Telemetry has two key
advantages over other methods of monitoring: the ability to individually identify study
animals without capture and the ability to reliably relocate study animals.
Prior telemetry studies have focused on adult R. pretiosa, because of the need to
maintain a transmitter to bodyweight ratio of less than 10%. Transmitters available in
the past were too heavy to attach to juveniles, but recent advances in technology have
produced transmitters that weigh approximately half a gram allowing them to be
attached to juvenile R. pretiosa. These smaller transmitters make it possible to gather
information on movements and habitat use of sub‐adult R. pretiosa. Information
gathered from telemetry will be used to help guide future management of R. pretiosa
on and off JBLM as well as aid in selecting future reintroduction sites.
While telemetry has many advantages over other monitoring techniques, the
impact of the transmitter attachment is a major weakness. The delicate skin of ranid
frogs can make safe telemetry particularly difficult. Improperly attached transmitters
can cause severe injury and even death. Currently, an insufficient body of literature
exists on transmitter attachment methods for ranid frogs making it difficult to select an
appropriate attachment method. Many studies involving telemetry either fail to
describe the attachment technique in detail or fail to report results on how successful
3
the selected attachment method was in preventing injuries or dropped transmitters. In
an effort to expand the knowledge on transmitter attachment methods for ranid frogs,
three attachment methods were used during telemetry on JBLM and injury rates were
recorded.
Due to the delicate nature of the skin of ranid frogs, great care must be taken to
prevent injury from transmitter attachments. The need to prevent injury led to frequent
capture and handling of study animals. Little is known about the impact frequent
handling has on the behavior of transmittered individuals. Studies of amphibians have
found that habitat selection is influenced by many factors including the need for
protection from predators (Bloomquist and Hunter 2010). If frogs perceive researchers
as predators, it is possible that habitat selection will be different for those study
animals. If capture and handling influences the behavior of transmittered frogs, it is
possible that data gathered via telemetry are biased. During the fall of 2009, in an effort
to shed light on the impacts of frequent handling on movements of transmittered frogs,
data were gathered on the daily distance traveled following capture and compared to
the daily distance traveled without capture.
Background
Global Amphibian Decline
Researchers across the world have reported rapid, large‐ scale declines in
amphibian populations. The first reports of large scale amphibian declines surfaced
during the late 1980’s, although many declines began in the 1970’s (Blaustein and Wake
4
1990). Recent publications (IUCN; Kriger and Hero 2007; Lips et al. 2008) give ample
evidence of worldwide decline: 1) one third of the world’s 6,140 amphibian species are
classified as threatened, and 43% of all species are in decline; 2) there is little or no
evidence that populations have begun to rebound from recent losses; 3) currently less
than one percent of amphibian species are increasing. In many cases, declines have
been extremely rapid with populations collapsing in a matter of months (Lips et al.
2006). In the last 50 years, rates of amphibian extinctions are up to 97 times higher
compared to the previous 500 years (Kriger and Hero 2007B). The relatively compressed
time scale of global declines coupled with the rapid increase in extinction events is
unprecedented in current ecological history (Collins and Storfer 2003).
The loss of amphibians will have far reaching ecological impacts on the
ecosystems they inhabit. In some ecosystems, larval amphibians make up the majority
of herbivores and their loss could lead to increased algal growth. An increase in algal
growth could in turn lead to eutrophication and hypoxia. Loss of amphibians will also
alter higher trophic level food webs. Many adult amphibians are major predators of
insects, and amphibians provide an important food source for many other species in the
ecosystems they inhabit (Johnson 2006).
Amphibians also serve as indicator species for the overall health of ecosystems.
In general, amphibians are highly sensitive to changes to their environments making
them excellent indicators of increased environmental stresses including pollution and
habitat degradation (Blaustein and Wake 1994). The global collapse of amphibian
5
species has led many researchers to question the overall health of the biosphere and to
fear that amphibians are just the first of many genera to suffer declines.
In the United States, 21% of the 272 native species of amphibians are threatened
or extinct. Declines have been most severe in the western part of the USA. In the Sierra
Nevada of California, a 98% decrease in populations of yellow legged frogs (Rana
muscosa) has been reported between the mid 1970’s and late 1980’s. Other amphibian
species in the west have undergone similar declines. In Oregon, 80% of the thirty
populations of cascade frogs (Rana cascadae) that have been monitored since the mid
1970’s were extirpated by 1990 (Blaustein and Wake 1990).
Declines are driven by a multitude of factors that are species and context
dependent (Collins and Storfer 2003; Rollins‐Smith and Conlon 2005). Causes of
amphibian decline can be grouped into six major categories, including habitat
alterations and destruction, overexploitation, impact of exotic species, global
environmental changes, chemical exposure, and emerging infectious diseases (Collins
and Storfer 2003). A graph of the major causes of global amphibian decline can be found
in Figure 3. As can be seen from the graph, habitat loss has by far the largest impact on
amphibian species declines followed by pollution. Disease only accounts for a small
portion of the overall impact on amphibian species, although the majority of species
affected by disease are also threatened.
6
Major Causes of Global Amphibian Declines.
Figure 1: Major causes of global amphibian decline and the number of species affected by
each cause. Threatened species are represented by the red portion of the graph. Source IUCN
http://www.iucnredlist.org/initiatives/amphibians/analysis/major‐threats
Decline of Oregon Spotted Frogs
R. pretiosa has been extirpated from between 78% and 90% of their original
range. Much of this decline is the result of habitat loss and fragmentation. Over the last
150 years, much of the habitat used by spotted frogs was converted to agriculture or
developed. This is especially true of lowland habitats such as those found in the Puget
Trough (Pearl and Hayes 2004). R. pretiosa rely on early successional wetlands. Many of
these wetlands have been altered through human activity and natural succession, both
7
of which reduce available habitat. European settlers diked and drained many emergent
wetlands that provided ideal habitat for R. pretiosa for use in agriculture and urban
development. Not all habitat loss can be attributed to human activity; natural
succession of wetlands from emergent to scrub shrub has led to a decrease in quality
and quantity of available habitat for R. pretiosa (McAlister and Leonard 1997). Invasive
species, both plant and animal, also play a role in the reduction of R. pretiosa through
increased predation, competition and changes in habitat structure. The extent of the
impacts of invasive species on populations of R. pretiosa is unclear.
In the late 1990’s and early 2000’s, populations of R. pretiosa in Washington
exhibited multi‐year declines in the number of egg masses laid. These declines led
biologists to become increasingly concerned about the continued viability of R. pretiosa
in Washington. At Conboy Lake, the largest known population of R. pretiosa in
Washington, the number of egg masses plummeted from just over 7,000in 1998 to
slightly under 1,500 in 2002 (USFWS 2010). Furthering the concern over declines of R.
pretiosa was the fact that specimens collected at Conboy Lake following an observed die
off of frogs tested positive for the amphibian chytrid fungus Batrachochytrium
dendrobatidis (Bd). Subsequent testing found Bd at the three known R. pretiosa sites in
Washington. The presence of Bd at all sites led to concerns that Bd was the proximate
cause of declines throughout the region and that Bd would drive R. pretiosa to
extinction. Concerns over Bd are now being reduced after preliminary research
indicated that R. pretiosa from Conboy Lake are very tolerant of Bd exposure and are
capable of shedding the infection (Padgett‐Flohr and Hayes 2011). Despite these test
8
results, it is possible that Bd caused the die offs of R. pretiosa observed at Conboy Lake
leaving only resistant animals to test. Even if Bd caused the die off at Conboy Lake, the
results of Padgett‐Flohr and Hayes (2011) provide hope that the remaining resistant
frogs will rebound.
While there are many contributing causes of recent declines, the specific cause
of recent decline is not yet known. It is likely that all listed impacts have played some
role in recent population declines of R. pretiosa in Washington.
Conservation Status
The Oregon spotted frog has suffered significant population declines throughout
its entire range resulting in legal protections for the species in all three states where it
occurs and in Canada. R. pretiosa is designated as Sensitive‐Vulnerable in Oregon, State
Endangered in Washington, Species of Special Concern in California, and Endangered in
Canada.
In 1993, prior to splitting the spotted frog complex into distinct species, the
United States Fish and Wildlife Service (USFWS) determined that four distinct
populations of spotted frogs within the larger spotted frog complex warranted listing
under the Endangered Species Act (ESA). Included in these sub‐populations was the
pacific coast sub‐population, later given full species status as R. pretiosa. Despite the
determination of a need for listing, R. pretiosa was precluded from listing due to higher
priority species and lack of funding (McAllister and Leonard 1997). In 1997, following the
elevation of R. pretiosa to full species status, a USFWS review of R. pretiosa concluded
that listing under the ESA was still warranted but once again was precluded due to lack
9
of funding and other higher priority species. Currently the Oregon spotted frog remains
a federal candidate species.
Current Conservation Actions:
Conservation actions are underway throughout R. pretiosa’s entire range. Much
of the conservation efforts for R. pretiosa have been focused on habitat restoration and
captive rearing. Captive rearing projects to augment existing populations as well as
establish new populations are part of the R. pretiosa recovery plans for Washington and
British Columbia. Captive rearing projects collect eggs from the wild and rear them
through metamorphosis after which they are released. Rearing protocols differ between
the two countries. The differences are focused on how to deal with predation on
released frogs. In Washington, size is favored over numbers while the opposite is true in
Canada. In Washington frogs are exposed to elevated temperatures in an effort to
head‐start their growth before release. This head‐starting, which often produces adult‐
sized frogs by the time of release, is designed to help reduce predation on newly
released individuals by reducing the number of predators capable of consuming
released frogs. In Canada, frogs are reared without artificial heat and therefore are
much smaller at release. The lack of heat reduces husbandry costs and allows for
greater numbers of frogs to be reared which compensates for increased predation rates
(Andrea Gielens personal communication 2010). In addition to this difference in rearing
protocols, the two programs differ with respect to where captive reared frogs are
released. In Canada, captive reared frogs are used to augment existing populations,
while in Washington efforts are directed towards establishing new populations (Andrea
10
Gielens personal communication 2010). Biologists in Washington believe that expanding
the number of localities with R. pretiosa reduces chances of regional extirpation. The
captive rearing program in Washington is entering its fourth year with a total of 2,363
frogs released into Dailman Lake and Muck Creek on JBLM. Releases on JBLM are
expected to continue through 2012, at which time the project will be assessed and the
need for additional releases will be determined. If additional releases are not needed,
then a second release site will be selected. In the spring of 2011, biologists located 11 R.
pretiosa egg masses at JBLM which represented the first signs of breeding as a result of
the project. The fact that breeding has occurred at the first reintroduction site is a
positive sign. Conservation partners are thus cautiously optimistic that reintroduction
efforts have been successful.
Substantial effort has been put into R. pretiosa recovery throughout its range. In
recent years, populations of spotted frogs in Washington have shown signs of recovery
with egg masses trending upward for all three populations where long term monitoring
has occurred; however, none of the populations have reached the peak pre‐crash levels.
11
Geographical Distribution
Figure 2: Historic and Current Distribution of R. pretiosa. Data are from
Cushman and Pearl 2007, and McAllister and Leonard 1997.
12
Historically R. pretiosa ranged from Southwestern British Columbia to
Northeastern California and was widely distributed throughout the Puget Trough and
Willamette Valley (Figure 2).
Habitat loss and fragmentation has resulted in R. pretiosa being lost from
between 78% and 90% of their historic range (McAllister and Leonard 1997). The
literature on R. pretiosa gives varying numbers of current locations ranging from 33 to
43. The range in the number of locations of R. pretiosa is caused by how breeding sites
are counted. Some publications combine sites based on what are believed to be
populations while others include all known breeding sites (Pearl et al 2009, White 2002,
USFWS 2010). While the exact number of extant populations of R. pretiosa is unclear it
is known that the majority occur along the Cascades in Central Oregon. As much as two
thirds of known populations of R. pretiosa are located along the cascades in Central
Oregon (Pearl et al 2009). The number of locations for R. pretiosa is difficult to
determine because increased survey efforts have found several new populations in
recent years that are not reflected in this total.
Currently, five populations of R. pretiosa are known to exist in Washington, two
of which were discovered in 2011. Populations of R. pretiosa are known to occur along
the Black River in Thurston County, at Trout Lake and Conboy Lake in Klickitat County
and within the Nooksack and Samish watersheds in Whatcom County. The discovery of
R. pretiosa in Whatcom County is the result of increases in survey efforts that led to the
discovery of four oviposition sites. These four sites represent two additional
populations, but the exact size of these populations has yet to be determined (Jennifer
13
Bohannon personal communication 2011). Early signs indicate that a sixth population
may have established on JBLM as a result of re‐introduction efforts. Despite these
recent positive trends, populations of R. pretiosa in Washington remain in a perilous
position. The majority of R. pretiosa occur at three sites which makes them vulnerable
to stochastic events and extirpation.
Taxonomy and Genetics
R. pretiosa is a member of the order anura, the family ranidae and the genus
Rana, or true frogs. The genus Rana incorporates the majority of North America’s larger
frogs (McAllister and Leonard 1997).
R. pretiosa was first described in 1853 by Baird and Girarad from specimens
collected near the site of Fort Nisqually (McAllister and Leonard 1997). When first
classified taxonomically, the species Rana pretiosa included what are now three distinct
species, Oregon spotted frog (R. pretiosa), Columbia spotted frog ( R.luteiventris) and
Cascades frog (R. cascadae). The first of these species was separated from R. pretiosa in
1939 by Slater when he described the cascade frog (R. cascadae). The Columbia and
Oregon spotted frogs remained as subspecies of R. pretiosa until 1995 when genetic
analysis was used to elevate these two subspecies to species status (Green et al 1996).
Historic references and museum samples of R. pretiosa can be misleading due to
the above noted taxonomic changes. Further complicating the historic record is the fact
that R. pretiosa and R. luteiventris are not simply subspecies that have been elevated to
full species status. The work conducted by Green et al. (1996) divides the two species
differently than the subspecies were divided. This confusion can make it difficult to
14
determine historic ranges and localities for these three species which makes it difficult
to determine the exact level of declines for R. pretiosa.
When compared to other species of ranids, R. pretiosa exhibit low genetic
diversity throughout their range. R. pretiosa likely exhibit high levels of genetic isolation
because of their highly aquatic life history which limits dispersal between watersheds
(Blouin et al 2010). Recent genetic analysis revealed three major groupings of R.
pretiosa: the Northern group, which includes populations from British Columbia to
Camas prairie in northern Oregon, the Central Cascades group in Central Oregon, and
the Klamath Basin group in southern Oregon (Blouin et al 2010). The Northern group
can be further broken down into four unique subgroups: British Columbia, Chehalis
River, Columbia River and Camas prairie, making for a total of six genetically distinct
populations of R. pretiosa throughout its range. Isolation of these six groups occurred
prior to European influence and the lack of genetic diversity is not the result of habitat
fragmentation caused by European settlement (Blouin et al 2010). More recently,
habitat fragmentation has further isolated the majority of remaining R. pretiosa
populations and further reduced genetic exchange. Meta‐population dynamics only
exist in three locations: the Chehalis drainage, Central Cascades and the Klamath River
basin (Blouin et al 2010). The lack of meta‐populations leads to an increased risk of local
extinctions.
Species Description
Adult R. pretiosa range in size from 44 to 100mm snout to vent length, with
females attaining larger sizes than males (Lict 1974; McAllister and Leonard 1997).
15
Individuals over 100mm are rare, but do occur. The largest R. pretiosa on record, a
female from Conboy Lake measured 107.5mm and weighed 100.5 g (Rombough et al
2006). A study of three populations of R. pretiosa in Washington found that females
were an average of 14mm larger than males (McAllister and Leonard 1997).
Coloration of R. pretiosa varies with age and location. Dorsal coloration of juvenile R.
pretiosa ranges from olive green to reddish brown. As individuals age they tend to
develop more reddish coloration on their dorsal side. Older individuals are often brick
red on their backs with ragged black spots (Figure 3).
Figure 3: Dorsal view of R. pretiosa. Note the presence of a
telemetry attachment belt around the hips.
Black spots with light centers are present on the head and back and become darker and
more ragged edged in appearance with age. Dorsal lateral folds are present and extend
from the eye approximately half way down the back. R. pretiosa have a white to tanish
16
throat and chest which transitions to red on the belly and legs (Figure 4). Older
individuals tend to have more extensive red colorations on their under parts (McAllister
and Leonard 1997).
Figure 4: Ventral view of R. pretiosa: Photo by Gary Nafis Source:
http://www.californiaherps.com/frogs/pages/r.pretiosa.html
Male and female R. pretiosa are similar in coloration and can be difficult to
distinguish, especially as juveniles. Distinguishing the sexes of R. pretiosa becomes
easier as they reach adulthood. Sexually mature males can be distinguished from
females by the presence of nuptial pads on their thumbs and stouter forelimbs.
Several species of ranid frogs are very similar in appearance and have ranges
which are adjacent to, or overlap with, R. pretiosa making field identification of
individuals difficult. R. pretiosa are similar in appearance to the cascades frog, Columbia
17
spotted frog and the northern red‐legged frog (R. aurora). R. pretiosa in western
Washington are most likely to be confused with the northern red‐legged frog due to
their sympatric existence. R. pretiosa can be distinguished from northern red‐legged
frogs by the presence of full webbing on their hind feet, up turned eyes, and lack of
mottling on the groin patch (Figure 5). For an extensive explanation of how to
differentiate all life stages of similar species to R. pretiosa see McAllister and Leonard
1997.
Figure 5: Comparison of groin patch for R. pretiosa and R. aurora. R.
pretiosa is on the right: Source Washington Herp Atlas Photo by D.
Hagin
18
Natural History
R. pretiosa are a highly aquatic amphibian spending little time outside of
wetlands. In one study using radio telemetry, frogs were found in areas without
measurable water 1.4% of the time (n=295), and over land movement was only
observed once (n=645) (Watson et al 2003). Populations of R. pretiosa are associated
with wetlands greater than four hectares in size where some form of permanent water
is present (Pearl and Hayes 2004). Habitat use by adult R. pretiosa varies with season
and directed seasonal movements occur between habitat use areas (Pearl and Hayes
2004). During breeding season, R. pretiosa use shallow seasonally inundated areas while
during the summer they retreat to areas of permanent water (Watson et al 2003).
Overwintering generally occurs in lotic habitats or areas of ground water up‐welling
(Pearl and Hayes 2004). The need for permanent water greatly limits the amount of
suitable wetlands within the range of R. pretiosa (Pearl and Hayes 2004). When in
deeper water, R. pretiosa prefer areas with floating aquatic vegetation which provide
refuge from predators as well as concealment from potential prey (Lict 1986, Pearl et al
2005).
R. pretiosa reach sexual maturity two to three years after metamorphosis with
females maturing later than males (Lict 1974; McAllister and Leonard 1997). In Canada,
females reach maturity at 63mm while males are mature at 46 mm (Lict 1974). R.
pretiosa breed explosively during the late winter to early spring. The timing of breeding
is closely correlated to water temperature so the exact timing is variable throughout
their range (Chelgren et al 2008; White 2002; McAllister and Leonard 1997). Water
19
temperatures at time of first oviposition for populations along the Black River in
Thurston country ranged from 47 to 52 degrees Fahrenheit (McAllister and Leonard
1997).
Eggs are laid in communal oviposition sites where as many as 75 egg masses are
laid in a single cluster (McAllister and Leonard 1997). The average fecundity of R.
pretiosa is around 600 eggs per egg mass (McAllister and Leonard 1997; Lict 1974).
Males arrive at communal breeding sites first and begin calling to attract females
(McAllister and Leonard 1997). The call of R. pretiosa is a soft clucking sound and has
been described as similar to a woodpecker tapping on a distant tree. R. pretiosa
oviposition sites are generally located along the shallow margins of seasonal ponds and
stream edges. Eggs are typically deposited in water between 5.9 and 25.6 cm in depth
(Pearl and Hayes 2004), but breeding has been observed on top of reed canary grass
mats in areas of deep water (pers. obs). Deeper water will be used for oviposition if
mats of vegetation are present that allow the frogs to place eggs in the top of the water
column (personal observation). R. pretiosa use of shallow seasonal pools leaves eggs
vulnerable to desiccation and freezing, making egg survival rates highly variable from
year to year. In drought years, it is possible for an entire year’s breeding to fail (Lict
1974). R. pretiosa appear to show site fidelity with communal oviposition sites being
used for multiple years.
Eggs usually hatch within 18‐30 days of oviposition, depending on water
temperature. Once hatched, tadpoles remain attached to the jelly for several days
20
before becoming free swimming. As free swimming tadpoles, R. pretiosa are primarily
herbivores, feeding extensively on algae.
Until metamorphosis is complete, R. pretiosa remain vulnerable to receding
water levels. In typical years, tadpoles metamorphose 13‐16 weeks after hatching. At
this point, young of the year (YOY) R. pretiosa are capable of dispersing from seasonal
pools to more permanent water bodies (McAllister and Leonard 1997). Once
metamorphosis is complete, R. pretiosa become primarily carnivorous, feeding on
insects, macro invertebrates, and other amphibians.
R. pretiosa are primarily ambush predators who feed opportunistically on
available prey items. R. pretiosa have been known to eat juvenile western toads and
hatchling tadpoles of their own kind (Pearl and Hayes 2002). During captive rearing, R.
pretiosa were observed cannibalizing smaller individuals in their holding tanks. This
cannibalistic feeding is not uncommon amongst ranid frogs.
Post‐metamorphic R. pretiosa are known to feed on a variety of organisms
including: leaf beetles (Chrysomelidae), ground beetles (Carabidae), spiders
(Arachnidae), rove beetles (Staphylinidae), syrphid flies (Syrphidae), long‐legged flies
(Dolichopodidae), ants (Formicidae), water striders (Gerridae), dragon flies (Odanata)
and damselfly (Coenagrionidae) (McAllister 1997; Pearl et al 2005).
R. pretiosa use two methods for capturing prey. Frogs will either sit and ambush
prey that comes within range of attack or actively stalk prey. R. pretiosa have been
observed stalking prey by slowly moving towards food items with only their eyes above
21
water (Pearl et al 2005). Frogs will also locate a prey item and dive, surfacing close to
the prey. In either case, prey is attacked with a lunging motion.
Different life stages of R. pretiosa are predated by different organisms. Primary
predators of adult R. pretiosa include garter snakes (Thamnophis spp), bullfrogs
(Lithobates catesbeianus), great blue herons (Ardea herodias), green herons (Butorides
virescens), raccoons (Procyon lotor), belted kingfishers (Ceryle alcyon), sandhill cranes
(Grus canadensis), coyotes (Canis latrans), striped skunks (Mephitis mephitis), mink
(Mustela vison), and river otters (Lutra canadensis)( Lict 1974).
Study Area:
22
Figure 6: Radio telemetry study area on JBLM. Releases of R. pretiosa
for telemetry occurred at Dailman Lake
Dailman Lake and associated wetlands cover approximately 300 acres on Joint
Base Lewis McChord and are part of the Muck Creek drainage. The wetland complex
consists of five distinct water bodies which are hydrologically connected on a seasonal
basis via Muck Creek and other small channels (Figure 6). During summer, these
wetlands become isolated as water levels drop. Wetlands in this complex are dominated
by emergent vegetation with cattail (Typha latifolia), hard stemmed bulrush
(Schoenoplectus acutus), reed canary grass (Phalaris arundinacea), pond shield
(Potamogeton spp), sedges (Carex spp), rushes (Juncus spp), and Eurasian watermilfoil
(Myriophyllum spicatum) accounting for the primary vegetation. Water levels in the
study area have large seasonal fluctuations of several meters fed by ground water.
Water levels generally begin to rise significantly in December and remain high through
May before beginning to recede. Low water generally occurs in October(personal
observation).
Telemetry
Remote tracking, which includes radio telemetry, is increasingly becoming a
cornerstone of wildlife biology. Remote tracking allows biologists to gather information
such as movements, habitat selection, home ranges, and migrations of cryptic species
23
that would otherwise be extremely difficult to gather (Rowely and Alford 2007).
Telemetry is similar to a high‐tech game of hide and seek which works on the same
concept as household radios. Transmitters emit a signal that is picked up by a receiver as
an audible beep. Each transmitter has its own specific frequency which allows individual
animals to be identified. Individual animals are tracked by tuning the receiver to their
frequency much like changing stations on a radio. Animals are tracked using directional
antennas that allow researchers to determine the direction of the strongest signal. By
following the strongest signal, exact locations of animals can be discovered. Like all
monitoring techniques, telemetry has its weaknesses. The largest drawback is
transmitter weight which limits the size of animals that can be used in telemetry studies.
Research has found that to prevent negatively impacting the fitness and behavior of
study animals, the weight of transmitter should not exceed 10% of the body weight of
animals studied (Richards et al 1994). A second drawback to telemetry is the risk of
injury to study animals. Attachment of telemetry transmitters can open sores to
develop.
Methods:
In this study, habitat use, movement, and dispersal of juvenile R. pretiosa were
monitored using radio telemetry. Analysis of movements and dispersal is based on
average daily movements recorded during telemetry. Habitat use was assessed by
determining the habitat type used at the time frogs were located.
24
Statistical analysis
Statistical analyses were run using version 8.0 of JMP by SAS, Microsoft Office Excel
2007 and re‐sampling stats add‐on for Microsoft Office Excel 2007 by Statistics.com LLC.
Telemetry
During fall 2008, spring 2009 and fall 2009, juvenile R. pretiosa were tracked
using radio telemetry following their release into Dailman Lake on JBLM. Telemetry was
conducted by biologists from Washington Department of Fish and Wildlife and Joint
Base Lewis McChord Fish and Wildlife. BD‐2N transmitters from Holohil Systems Ltd (
http://www.holohil.com/ ) were used throughout the course of telemetry. During the
fall of 2008, telemetry occurred over two sessions with six frogs tracked the first session
and ten frogs tracked the second. All frogs were fitted with BD‐2N transmitters with a 28
day battery life. During the spring of 2009, eight frogs were fitted with BD‐2N
transmitters with a 28 day battery life and four were fitted with BD‐2N transmitters with
between 12 and 16 week battery life. In the fall of 2009, all 12 frogs were fitted with BD‐
2N transmitters with between 12 and 16 week battery life. A total of 40 frogs were
tracked over four tracking sessions. Transmitters with a 28 day battery life weighed
between .52 and .56 grams, and transmitters with a 12‐16 week life weighed between
1.4 and 1.5 grams. Minimum body weight for frogs fitted with transmitters was six
grams for units with 28 days of battery and 15 grams for the 12‐16 week units. For
telemetry on JBLM, transmitters were attached to frogs using three different materials.
Attachment methods were adapted from Lynch 2006. Transmitters were attached with
25
silk thread, 4mm or 7mm silk ribbon. Silk was selected as the attachment material
because it is a natural fiber that will break down in the environment over time allowing
frogs to eventually break free of transmitter attachments if they could not be
recaptured (Lynch 2006). Attachment material was threaded through a tube on the
transmitter and secured around the hips of a frog using an overhand knot (Figure 7).
Transmitters were secured snuggly but not tight enough to cause compression to the
abdomen.
Figure 7: 28 week BD‐2N radio telemetry transmitter attached to a juvenile
Oregon spotted frog (R. pretiosa)
In the fall of 2008, tracking occurred during two sessions. The first session lasted
from 22 September to 17 October while the second session ran from 14 November to 9
December. Six frogs were tracked during the first session and ten during the second. The
first tracking session was terminated after all transmitted frogs suffered injuries as a
result of transmitter attachments. During the first session, frogs were tracked daily for
the first week following release. Due to the relatively short distances frogs traveled
between tracking days, the tracking schedule was reduced to three times a week for the
duration of tracking including the second session. Attempts were made to recover frogs
26
on each tracking day in order to assess belt condition and determine if the frog was still
living. Mass and snout to vent length were recorded once a week.
During the spring of 2009, telemetry occurred from 8 April to 17 June. At the
beginning transmitters were attached to 12 frogs. This number was reduced on 17 April
to eight after it was determined that tracking 12 frogs in a day was not feasible due to
time and staffing constraints. Transmitters were removed from the first four frogs
captured. Frogs were tracked three days a week. Again, attempts were made to recover
frogs on each tracking day in order to assess belt condition and determine if the frog
was still living. Mass and snout to vent length were recorded once a week.
During the fall of 2009, 12 frogs were tracked following telemetry protocols
established during the spring of 2009. Telemetry started on 29 October and did not end
until 12 February. Frogs 331, 333, 336, 346 and 348 dropped transmitters within 15
days of the start of tracking. These five frogs were replaced with frogs still held at
rearing facilities. These frogs were fitted with transmitters and released on 17
November. The locations of frogs that dropped their transmitter prior to 17 November
were dropped from analysis of movements and number of tracking days but kept when
analyzing habitat use and dispersal. An extended freeze at the beginning of December
caused Dailman Lake to ice over which prevented tracking during December. Tracking
was resumed in January in an attempt to remove transmitters. Data on movement from
during January and February is excluded from analysis of movements. Frog 337 was
dropped from all analyses because of discrepancies in the data. During fall 2009, frogs
27
were only handled once a week in order to record belt condition, snout to vent length,
and mass.
During all telemetry sessions, attempts were made to locate all frogs each
tracking day; however, this was not always possible, so some frogs were located less
often. If a frog was not located on a tracking day it was tracked first the following
scheduled tracking day.
For all radio telemetry tracking sessions, locations of frogs were recorded using a
Trimble GEO XH hand held data logger and GPS. Locations were recorded to sub‐meter
accuracy
Movement
The distance moved by transmittered frogs was determined using the measure
tool in ArcGIS, and recorded to the nearest tenth of a meter. All distances were
measured in a straight line between locations and represent the shortest possible
distance traveled. The daily distance from last tracking was calculated by dividing the
distance traveled between trackings by the number of days between trackings. Average
daily movement was calculated by dividing the total distance traveled during the
tracking period by the number of days the frogs had transmitters. To compare
movement between tracking sessions the pooled average of the daily distance from last
tracking was used. Comparisons of daily movements within tracking sessions and
average daily movement between tracking sessions were carried out using ANOVA in
JMP.
28
Habitat Use
When frogs were located during radio telemetry, the primary macro habitat
being used was recorded. Habitats were classified into 15 categories: emergent,
emergent aquatic, emergent terrestrial, floating aquatic, forested wetland, muck, muck
edge, mud puddle, open water, open water>1m, scrub shrub, upland, wetland edge,
wetland edge aquatic, wetland edge no water, and wetland edge terrestrial. Habitat
categories are defined in Appendix A. If a frog was found using a habitat that did not
meet the definition of an existing habitat category a new habitat category was created.
Along with the primary macro habitat the dominant vegetation of the area was
recorded. Vegetation was grouped into categories based on structure. If vegetation
species could be identified it was recorded and categorized. Vegetation groups included:
low groundcover, floating aquatic, rush, sedge, reed canary grass, pond shield, pond lily,
bull rush, and grass.
Habitat classification varied between years. As experience with tracking
increased so did the detail of habitat categories. During 2008, many frogs were classified
as wetland edge that would have been classified as emergent in 2009. This was due to
the fact that in 2008, the emergent category was not included as a habitat type so frogs
not near the edge of standing water, yet still well within the wetland boundary, were
classified as wetland edge. During 2008, no distinction was made between frogs utilizing
aquatic or terrestrial habitats along wetland edges and in emergent areas. In an effort
to create a more consistent data set, habitats were changed to match those of 2009
when enough information was available to do so. Conversions were completed based on
29
notes taken at the time of tracking, presence of standing water at frog locations and the
dominant vegetation. For example, the habitat for a frog classified as wetland edge in
2008 which was located within the wetland boundary with a dominant vegetation of
rush with no standing water was reclassified as emergent terrestrial for data analysis
purposes.
During spring and fall of 2009, frog locations that occurred within a half meter of
the water line were classified as either wetland edge terrestrial or wetland edge aquatic.
Frogs more than half a meter from water and outside the wetland boundary were
classified as upland. If emergent vegetation was present and frogs were located more
than a half meter from the water line they were considered to be using emergent
terrestrial or emergent aquatic.
Available habitat during each tracking session was not determined due to
fluctuating water levels which influenced the amount and types of available habitats.
This large change in habitat type and availability within tracking periods made analysis
of habitat selection unreliable. Thus, comparisons of habitat use between and within
tracking sessions were not conducted.
Transmitter attachment materials
During the first tracking session of fall 2008, all transmitters were attached using
silk thread (n=6). In an effort to create a thicker attachment material and reduce the risk
of injury, 8 strands of thread were used on each attachment. This failed to prevent
injury as all animals suffered abrasions within 25 days of release, with the majority of
animals suffering injuries sooner. In an effort to reduce injury, thread was dropped as a
30
transmitter attachment material and only 4mm and 7mm silk ribbon was used during
the second session. This greatly reduced injury with only one animal with a 4mm belt
showing signs of abrasion. Unfortunately data on how many frogs were fitted with each
type of belt were not recorded. During the spring of 2009, an effort was made to
determine if injury rates differed for transmitters attached with 4mm or 7mm ribbon.
Transmitters were attached to six frogs using 4mm ribbon and six frogs using 7mm
ribbon. Animals were captured as often as possible to assess if injury had occurred. Any
signs of abrasion were recorded. The first signs of abrasion were defined as white
patches of skin under belt attachments. Transmitters were removed once abrasion was
observed. Data were analyzed using a Chi‐square test.
Affects of capture on frog movement
The affect of frequent capture on frog movements was studied during the fall of
2009. Frogs were only captured once a week and efforts were made to reduce habitat
disturbance on days frogs were not captured. A frog was considered to be captured if
its habitat was disturbed enough to alter the structure or if the frog was handled. Re‐
sampling statistics for Microsoft Excel 2007 was used to create a bootstrap t‐test to
determine if the average daily movement following capture differed from the average
daily movement without capture. Frogs were pooled and treated as a single frog.
Analyses of movements following capture were run with and without frog 335. Frog 335
was excluded from analysis because of its use of a mud puddle which potentially acted
as a trap to keep it in a confined area masking the impacts of capture.
31
Results and Discussion
Habitat Use
Habitat use data are presented separately for all three tracking periods. Results
were not combined due to differing habitat conditions encountered during each
tracking period. For example, during the fall of 2008, frogs were observed using muck
33 times (n=138), but in the spring and fall of 2009 frogs were observed using muck only
once (n=188). The reduction in the use of muck was the result of the lack of available
muck habitat during the spring and fall of 2009. During both these tracking sessions,
water levels were elevated to the point that muck was not available or its availability
was greatly reduced. Frogs utilized 15 habitat types during radio telemetry with
variations of emergent and wetland edge accounting for the majority of all frog
locations (Table 1).
32
Table 1: Number of observations and % use of 15 habitats recorded during radio telemetry. *
indicates those habitat categories not used during all three tracking sessions.
Oregon Spotted Frog Habitat Use
Fall 2008 Number
Habitat Type of Observations /
% Use
Spring 2009
Number of
Observations / %
Use
Fall 2009
Number of
Observations / %
Use
Emergent
1/0.7%
0
1/0.9%
Emergent
Aquatic
1/0.7%
37/45.1%
14/13.2%
Emergent
Terrestrial
27/19.6%
1/1.2%
3/.9%
Floating Aquatic
1/0.7%
0
0
Forested
Wetland
0
8/9.7%
0
Muck
33/23.9%
0
1/0.9%
Muck Edge*
2/1.4%
0
0
Mud Puddle*
0
0
5/4.7%
Open Water
27/19.5%
1/1.2%
26/24.5%
Open Water>1m
0
0
3/2.8%
Scrub Shrub
0
1/1.2%
4/3.7%
Upland
2/1.4%
1/1.2%
24/22.64%
Wetland Edge*
6/4.3%
2/2.4%
0
Wetland Edge
Aquatic
0
24/29.2%
7/6.6%
Wetland Edge No
Water*
40/28.9%
0
0
33
Wetland Edge
Terrestrial
0
7/8.5%
18/16.9%
Total
Observations
138
82
106
Fall 2008
During the first session, six frogs were tracked for an average of 16 days. Fifty‐six
locations with macro habitat data were recorded during the first session. During the
second session, ten frogs were tracked for an average of 20 days with 82 locations
recorded. When both tracking sessions are combined, 138 frog locations were recorded
during telemetry in the fall of 2008. Throughout tracking, all frogs remained within or in
very close proximity to Dailman Lake. Frogs used 11 different habitat types. Wetland
edge no water (26%), muck (24%), open water (20%) and emergent terrestrial (14%)
accounted for 84% of the total habitats used (Table 1). Frogs were recorded using
habitats without measurable water 47% of the time, with the majority of these locations
occurring within the wetland boundary (Table 2). Frogs in habitat classified as muck
were considered to be in aquatic habitats even if standing water wasn’t recorded.
Table 2: Terrestrial habitat use recorded during radio telemetry. Habitats without measurable
standing water were considered to be terrestrial with the exception of muck.
Terrestrial Habitat Use
Tracking Session
Terrestrial
observations/Total
observations
%Terrestrial habitat use
34
Fall 2008
65/138
47.10%
Spring 2009
9/82
10.90%
Fall 2009
45/106
42.45%
Total
119/326
36.50%
The use of terrestrial habitats was observed during both tracking sessions in the
fall of 2008. During the first tracking session, frogs 602 and 607 moved away from
standing water into emergent terrestrial habitat. These frogs were between 10 and 50
meters away from standing water for multiple tracking days and remained away from
water until transmitters were removed. Frogs during the second tracking session utilized
terrestrial habitat within and outside the wetland boundary. Frog 615 was observed at
the base of a large stump buried in leaf litter in upland habitat outside of the wetland
boundary. On two occasions, frog 617 was located elevated above the wetland in
vegetation. Frog 617 was located in bull‐rush 24 cm above the surface of the wetland
and a second time 10 cm above the wetlands surface in reed canary‐grass stems.
Spring 2009
During the spring of 2009, 12 frogs were tracked for an average of 32 days.
Between 8 April and 17 June, 82 frog locations in nine different habitats were recorded.
Of the nine habitats used, emergent aquatic (45%) and wetland edge aquatic (29%)
accounted for 74% of habitats used by frogs. No other habitats were used more than 9%
of the time (See Table 1). Frogs were located in terrestrial habitats 10.9% of the time
(see Table 2). A single upland location was recorded during spring tracking.
35
On April 17, frog 612 was found concealed under duff within six inches of a small
garter snake, a known predator of R. pretiosa. Both frog 612 and the small garter snake
were on top of an ECO‐block that is part of the culvert over Muck Creek at Nixon
Springs.
Fall 2009
In the fall of 2009, 12 frogs were fitted with transmitters and tracked for an
average of 23 days. Between 29 October and 30 November, 106 frog locations in 11
different habitat types were recorded. Open water (24.5%), upland (22.64%), wetland
edge terrestrial (16.9%) and emergent aquatic (13.2%) accounted for 77.24% of the
habitats used (See Table 1) Frogs were recorded using terrestrial habitats 42.34% of the
time during the fall of 2009 (see Table 2). This is comparable to the amount of terrestrial
habitats used in fall, 2008.
The increase in use of upland habitat observed during the fall of 2009 is
particularly interesting. Multiple frogs were observed using habitats outside of the
wetland boundary for multiple days. Six frogs were located in upland habitats at least
one time during tracking. Frogs 349, 348, 347,335,334, and 331 all used upland habitat
to varying degrees.
On November 6, frog 335 moved upland to a large puddle in the dirt road that
leads to Dailman Lake and remained near this puddle for the duration of tracking. Prior
to taking up residence in the puddle, frog 335 had occupied several other upland
habitats including a roadside ditch and leaf litter under a big leaf maple (Figure 9).
36
Figure 8: Locations of Frog 335 during fall 2009 telemetry. Note the
clustering of points around a mud puddle in the lower part of the map.
37
During all three tracking periods telemetered frogs favored edge habitats over
those in the central part of the wetland. When found in open water, frogs were
associated with some form of floating aquatic vegetation that provided refuge from
predators. In the spring, frogs used terrestrial habitats at a lower rate than during the
fall tracking sessions.
R. pretiosa is considered a highly aquatic species that seldom ventures far from
standing water. The close association of R. pretiosa with standing water is thought to be
the result of feeding and escape behavior (Lict 1986b: Pearl et al 2005). Terrestrial
habitat use data from telemetry on JBLM is anomalous when compared to other habitat
use studies of R. pretiosa which found little or no overland movement and limited use of
terrestrial habitats (Watson et al 2003; Shovlain 2006).
During telemetry on JBLM, frogs were observed away from standing water
47.1%, 10.9% and 42.45% of the time during the fall of 2008, spring of 2009 and fall of
2009 respectively. When all tracking sessions are combined, as they were for Watson et
al 2003, terrestrial habitat was used 36.5% of the time (see Table 2). Five overland
movements were observed during telemetry. The number of overland movements
recorded only accounts for the initial move from aquatic habitat and does not account
for repeated overland moves of frogs that were using terrestrial habitats. If these
movements are included then the total overland movement is substantially higher with
31 probable overland movements (n=326). The substantial use of terrestrial habitats by
frogs released at Dailman Lake was in stark contrast to Watson et al 2003 which found
38
frogs away from standing water only 1.4% of the time (n=295) and only had one out of
645 observations that may have represented overland movements.
The increase in use of terrestrial habitats in this study compared to other habitat
use studies may be due to the fact that the study involved dispersal of juvenile frogs. All
other studies of R. pretiosa habitat use and movement have used adult frogs. The
observed increase in terrestrial habitat use and overland movement is possibly caused
by a specific behavior of juvenile R. pretiosa.
The increase in terrestrial habitat use during fall telemetry compared to spring
may be the result of increased availability of terrestrial habitats within wetland
boundaries during the fall. Water levels at the time of the fall releases are very near
yearly lows and aquatic connectivity between water bodies was greatly reduced while
availability of emergent terrestrial habitat was substantially increased which would
allow for greater use of this habitat. While fall telemetry was being conducted, aquatic
connectivity was only present between Hamilton Lake, Binocular Pond, and Dailman
Lake during both years. The lack of aquatic connectivity may have led frogs to disperse
terrestrially. During the spring of 2009, when water levels were up and aquatic
connectivity existed between all wetlands, the use of terrestrial habitats was greatly
reduced and the number of observed overland movements was much lower. The
reduced use of terrestrial habitats and overland movements is likely the result of frogs
using aquatic corridors for dispersal.
The use of terrestrial habitats by sub‐adult R. pretiosa warrants further research.
The hypothesis that aquatic refuge is the primary escape response of R. pretiosa
39
suggests that juveniles would potentially be more likely to remain near the safety of
standing water. Understanding the habitat requirements of sub‐adult R. pretiosa is vital
for future recovery efforts of the species.
Movement
Telemetered frogs made the largest movements during the spring of 2009, when
the average daily distance traveled was 53.46 m. In the spring of 2009, Frog 337 moved
330 meters upstream of the confluence of Muck Creek and Dailman Lake which marked
the furthest documented movement of a frog away from Dailman Lake during this study
(Figure 10).
Figure 9: Locations for frog 337 during the spring of 2009. Frog
337 moved the furthest distance away from the release point of
any frog tracked during this study.
40
Not all frogs made large movements during the spring of 2009. Frog 354
remained within several meters of the same location from 22 April to 17 June. During
this time, the average daily movement of frog 354 was 5.9m. The lack of movement
suggested a slipped transmitter or mortality, but frog 354 was recovered alive on June
17. The lack of movement may have been caused by injuries sustained from the
transmitter attachment. On April 15, frog 354 began to exhibit signs of abrasion from
the transmitter attachment. When Frog 354 was re‐captured on June 17th, open sores
were present in the groin area under the belt. The presence of wounds may account for
the lack of mobility, but it is possible that frog 354 simply found an area of high quality
habitat and remained until capture.
Comparisons of frog movements within tracking sessions did not reveal any
statistical significant differences in the average daily movements of individual frogs.
Comparisons of pooled average daily movements between tracking sessions found an
interesting connection between fall 2008 tracking and the 2009 fall tracking. Results
from ANOVA found that the average daily distance moved during the spring was greater
than movements in the fall 2008 and 2009 (F= 16.38, p=.0001) yet there was no
difference in movements for fall 2008 and fall 2009 telemetry (Table 3).
41
Table 3: Summary of daily distance traveled by frogs during radio telemetry. * Distances
traveled immediately following release were excluded from analysis of maximum distance
traveled. Numbers in red are statistically significant.
Tracking Session
Pooled Average
Daily Distance
Traveled (m).
Minimum/Maximum
daily distance traveled
(m)*.
Fall 2008 1st
Release
6.86
0.026/63.5
Fall 2008 2nd
Release
16.92
0.066/102.35
Spring 2009
53.46
0.166/277.5
Fall 2009
18.19
0.033/137
Water level appeared to relate to the distance that frogs moved. During the
spring when water levels were higher and aquatic connectivity existed between all
water bodies, frogs moved greater distances. This increased movement is likely the
result of the ease with which spotted frogs can travel through water compared to
overland.
Furthering the link between habitat conditions and movements of R. pretiosa is
the fact that frogs from fall of 2008 and fall of 2009 did not have significantly different
average daily movements despite a large difference in average size. Frogs released in
the fall of 2008 had an average mass of 7.33g while frogs released in the fall of 2009 had
an average mass of 31.5g. The fact that frogs tracked over similar time periods exhibited
similar movement despite a considerable size difference suggests that size does not play
42
a significant role in movements of captive reared frogs. This indicates that habitat and
other environmental conditions are the driving force behind movements of individual
frogs.
Dispersal
The dispersal of released frogs was mapped in an effort to determine the
availability of suitable habitat at the Dailman Lake release site as well as to see if
released frogs were clustering in any particular locations. During all tracking sessions,
frogs dispersed throughout the wetland complex and exhibited limited signs of
clustering. Frogs did cluster around the margins of wetlands, and during the spring frogs
clustered at the north end of Dailman Lake along the margins of Muck Creek. This
clustering along the margins of wetlands and streams fits with the expected behavior of
R. pretiosa. Dispersal appeared to be limited by available aquatic connectivity. Maps of
dispersal for all transmittered frogs can be found in Appendix B.
While frogs were detected using the majority of the available shoreline, frogs
didn’t appear to disperse evenly to all available habitats. During radio telemetry, frogs
were found in Hamilton Lake, Dailman Lake, Muck Creek, and Nixon Springs. Egg mass
surveys in the spring of 2011 found R. pretiosa egg masses in Shaver Lake. When egg
mass survey data are combined with telemetry data from all telemetry sessions, frogs
were located in all areas of the study site except Chambers Lake.
Frogs exhibited different dispersal patterns in the spring and fall. Frogs released
during the spring moved out of Dailman Lake and into Muck Creek where they traveled
upstream. A single location was recorded downstream of the confluence of Muck Creek
43
and Dailman Lake but that frog moved upstream by the next tracking day. Transmittered
frogs from the spring release did not move downstream into Chambers Lake despite a
perceived abundance of available habitat. In the fall of 2008 and 2009, the majority of
frogs remained within Dailman Lake. Several frogs moved into Binocular Pond and
Hamilton Lake but none entered Muck Creek. This dispersal pattern is likely the result of
water levels. In the fall Dailman Lake is hydrologically isolated from Muck Creek but
remains connected to Binocular Pond and Hamilton Lake. Frogs likely used this aquatic
connectivity while dispersing.
Juvenile dispersal may account for the high degree of terrestrial habitat use
observed during telemetry. During telemetry in the fall of 2008 and 2009 frogs were
observed making overland movements on multiple occasions. It is likely that these
overland movements were part of natural juvenile dispersal. While prior studies of R.
pretiosa have found little or no cross land movement, those studies were focused on
adult frogs (Watson et al 2003).
In many species the YOY are the primary drivers of dispersal to new habitats. It
is important for conservation actions to determine if YOY R. pretiosa are dispersing
terrestrially during the fall as a mechanism for colonizing new habitats. Further
understanding of how R. pretiosa move between wetlands will aid in creating corridors
to facilitate meta‐population dynamics in currently isolated sites.
Affects of capture on frog movement
Throughout the course of telemetry, frogs were captured on a regular basis to
determine if injuries were being caused by the attachment material. Analysis of distance
44
traveled following handling revealed that the frequent capture of frogs influenced the
rates of movement for telemetered individuals. The average daily distance traveled
following capture was 28.25m compared to 14.72m for un‐captured frogs. When the
average daily movements were analyzed using re‐sampling stats, the average distance
moved by frogs with and without capture was not statistically different (p=.068).
However when frog 335 was removed from analysis the average distance traveled
following capture changed to 32.58m compared to 12.78m without capture. When the
same re‐sampling stats were run without frog 335 the results indicated a significant
difference between the average movement with and without capture (p<.01). Frog 335
was removed from analysis of movements following capture because of its use of a large
mud puddle in a logging road. The use of this mud puddle by frog 335 indicated a
potential limited ability of that frog to move following capture. Frog 335 would have had
to make a large overland movement before it would reach another area with standing
water.
Further evidence of an impact of disturbance on frog movements can be found
in the data from spring 2009. Of the top ten daily distances traveled, nine occurred
immediately following release. Only two frogs, (611 and 618), did not make their largest
move between release and the first day of tracking.
The results of statistical analysis and daily distance traveled in spring 2009
suggest that researchers need to be exceedingly cautious when conducting telemetry
studies where study animals are repeatedly captured. Analysis of habitat use and
movements are potentially biased by increased movement caused by frequent capture.
45
During telemetry on JBLM, frogs appeared to exhibit a form of predator evasion by
making longer movements following capture. The need to evade a perceived predator
could have altered the habitat selection of telemetered individuals. It is also possible
that frogs were utilizing less than ideal habitats because they perceived that they had
been driven from preferred habitat by capture. Habitat selection in amphibians is
determined by many factors including predator evasion. If researchers were perceived
as predators it is likely they influenced habitat selection.
Due to the small sample size and lack of formal controls, results of this analysis
should be viewed as preliminary findings. Further research is needed to confirm the
results of this preliminary study.
Telemetry Attachment Material
Due to the delicate skin of amphibians, abrasions caused by transmitter
attachments can be a major concern for researchers (Muths 2003). Despite the
abundance of research using radio telemetry few papers detail how transmitters are
attached or the impacts of the selected transmitter attachment on research animals.
This lack of information makes it difficult for researchers to make the important decision
of what material to use and how to attach transmitters.
Reported attachment methods used on amphibians are variable and range from
ribbon tied around the hips of animals to belts sewn around the forelimbs. Both
synthetic and natural fibers are used for transmitter attachment, and include bead
chains, silk ribbon, cotton thread, medical adhesive strips and other stretchy material
(Watson et al 2003; Muths 2003; Shovlain 2006; Lynch 2006). While synthetic materials
46
offer a variety of properties that are useful for attachment, including elasticity, they do
not biodegrade which means researchers must recapture transmittered individuals and
remove transmitters. Natural materials such as silk will biodegrade, which allows
animals to break free of transmitter attachments and self release if researchers are
unable to recapture them or transmitters fail. The major drawback to using natural
materials is the fact that the majority of available natural materials lack elasticity which
makes sizing belts difficult. Improperly sized belts can negatively impact telemetry
studies in two ways. A belt that is too tight may constrict frogs and cause damage which
will affect behavior, while a belt that is too loose has an increased risk of prematurely
falling off resulting in a lack of data.
Of the attachment materials used, 7mm silk ribbon resulted in the fewest
injuries to frogs. Of six frogs with 7mm ribbon attachments, only one showed signs of
abrasion compared to three of six frogs injured with 4mm ribbon and six of six injured
with thread. A chi‐square test found a significant difference between injury rates for
transmitters attached with thread but not those attached with ribbon. While there was
no statistical difference between injury rates caused by 4mm vs. 7mm ribbon, the
sample size was very low. If the sample size were increased, it is possible that the
difference in injury rates would become statistically significant. The observed reduction
in injuries with 7mm ribbon is likely the result of the increased width of the attachment
material which helps prevent abrasion by providing a greater surface area where skin
contact is made reducing the ability of the material to constrict and cut into delicate
skin.
47
Injuries to frogs as a result of transmitter attachments could often be identified
prior to formation of open sores formed. Injuries followed a predictable pattern: first
the skin under the attachment belt would darken, then the skin would develop white
patches; finally open sores would develop. If the condition of frogs were monitored
closely, belts could be removed once white patches appeared and prevent the
occurrences of sores. The difficulty with this approach is that it required handling frogs
on a regular basis. Analysis of movements following handling shows that frogs made
larger movements following capture than if not handled. By using an attachment
method that reduces risks of injury, the need to capture frogs is reduced and therefore
so is the potential bias on movements caused by capture.
Silk was selected for attachment material because we believed it would
biodegrade and allow frogs to break free of transmitters if they could not be recaptured.
Based on observations made during the spring of 2009, silk ribbon performed as
expected with three transmitters breaking loose prior to removal. All three transmitters
were on animals for 70 days prior to the discovery of belt failure with all three belt
failures discovered on the same day. The silk that remained on the transmitter was
extremely brittle and broke easily when stressed. The grouping of this phenomenon
suggests that in aquatic conditions, attachments using silk ribbon will last about 10
weeks before animals can break free. The ability of frogs to self release is a major
strength of the use of silk belts. Animals often elude capture or transmitters
unexpectedly fail during telemetry making removal of transmitters difficult. The use of
48
natural fibers allows animals to survive even if transmitters fail or animals take up
residence in inaccessible areas.
Conclusion and Future Research Needs
This thesis results in three key conclusions regarding R. pretiosa and leads to two
key questions that warrant further research: 1) available habitat on JBLM appears to be
suitable to R. pretiosa, 2) habitat connectivity and variability is key for future
reintroductions, and 3) the use of wider natural fiber materials for transmitter
attachment has the least negative impact on study animals. This thesis also leads to two
questions that warrant further research: 1) the cause of increased utilization of
terrestrial habitats, and 2) the impact of frequent handling on behavior of study animals
during telemetry.
The use of captive breeding to recover R. pretiosa in Washington State appears
on the path towards success. Habitat use and dispersal patterns of post‐release R.
pretiosa indicate that Dailman Lake and the surrounding wetland complex provide
suitable habitat for sub‐adult R. pretiosa. The discovery of 11 R. pretiosa egg masses on
JBLM during the spring of 2011 indicates that breeding habitat is also available within
this wetland complex.
Gathering specific information on the ecology of all life stages of R. pretiosa is
important to furthering the recovery of this species. By gaining a better understanding
of habitat use, movements, and dispersal of a reintroduced population of juvenile R.
pretiosa, conservationists will be able to more easily manage existing populations and
49
select future reintroduction sites. Dispersal patterns at JBLM indicate that connectivity
of wetland habitats is key to successful reintroduction. By providing multiple
interconnected wetlands, released juvenile frogs were able to seek out suitable habitat
for later life stages. All oviposition sites found in 2011 were located outside of Dailman
Lake, which has been the primary release site.
Preliminary results from telemetry indicate that the use of relatively wide natural
fibers for transmitter attachment had the least negative impact on study animals. Silk
attachments performed as expected by allowing frogs to break free of transmitters if
they could not be captured. Telemetry is an inherently invasive monitoring technique
but researchers can reduce their impacts on study animals by selecting appropriate
attachment methods and taking care to properly attach transmitters. Using material
that provides both a relatively large surface area and is biodegradable is a good way to
protect study animals from harm.
Telemetry on JBLM produced multiple questions that warrant further
investigation. More research is needed into the utilization of terrestrial habitats by
juvenile R. pretiosa. Telemetry data indicates that sub‐adult frogs are utilizing a much
greater range of terrestrial habitats than previously documented. The role that
terrestrial habitats play in the overall ecology of R. pretiosa is unknown. It is possible
that the high use of terrestrial habitats at JBLM was caused by reared frogs being
introduced to a novel environment and that through the course of dispersal they moved
into areas that they would not have otherwise occupied. If the frogs had been reared
natively at this site, or if adult frogs had been released rather than young of the year, it
50
is possible that frogs would not have spent as much time in these habitats as was
recorded. Several frogs in this study spent the majority of their time in terrestrial
environments. A possible explanation for this use of terrestrial habitat is the need for
juveniles to disperse to new locations in order to establish new populations. If terrestrial
habitats are used by juvenile R. pretiosa for dispersal, then corridors can be designed
between existing populations and potential habitats in an effort to expand R. pretiosa
meta‐population dynamics.
Further research is needed to determine if the observed terrestrial habitat use is
indeed the result of juvenile dispersal. Anecdotal evidence collected during telemetry
suggests that the initial movement of frogs into terrestrial habitats was preceded by a
rain event. There is ample evidence in the literature of other amphibian species
dispersing terrestrially following rains. Efforts should be made to compare the timing of
overland movements with precipitation records to determine if rain fall is linked to
terrestrial habitat use.
The impacts of frequent handling on movements of telemetered frogs warrant
further study. The data for analysis were limited and patchy. Frogs were not captured
on a consistent schedule, which reduced the number of data points for each frog. Due
to a lack of data points for individual frogs, data for movements with and without
capture had to be pooled. By pooling data, the behavior of individual frogs could not be
determined and the movements of a single frog could sway results. As evidenced by the
removal of frog 335 from analysis, a single frog could have a large influence on the
51
outcome of this analysis. Future studies should strive to collect more data points for
individual frogs so data do not need to be pooled.
In our final conclusion, we note that the future of R. pretiosa in Washington
looks promising. The three previously known populations of R. pretiosa appear to be
rebounding from losses sustained in the late 1990’s and early 2000’s. The discovery of
two new populations in North Puget Sound coupled with the positive signs of success at
JBLM provides three new geographically distinct populations which reduces the risk of
extirpation. However, even given these positive trends a lot of work remains before R.
pretiosa could be deemed “recovered”. Even if recovery goals are met, active
management must be continued in order to maintain populations of R. pretiosa. This
study bolsters prior findings that R. pretiosa is dependent on early successional
wetlands that will require continued restoration activities to maintain. By applying the
knowledge reported in this thesis – knowledge gained through telemetry on JBLM, these
restoration activities can be designed to account for juvenile as well as adult habitat
needs.
52
Appendix A Definitions of Habitat Categories
Emergent: Emergent vegetation present, no reference to standing water.
Emergent aquatic: Standing water present but habitat dominated by emergent
vegetation
Emergent terrestrial: No standing water present. Dominated by emergent vegetation.
Floating aquatic: Habitat type used early in 2008 for frogs that were found in open
water with a large amount of floating aquatic vegetation.
Forested wetland: Wetlands located within forested areas.
Muck: Unconsolidated organic material.
Muck edge: Used in fall 2008 to describe frogs on the margin of muck habitat. This
category later became emergent terrestrial.
Mud puddle: Puddles in roads.
Open water: Little or no vegetation present. Surface cover is limited.
Open water>1m: Little or no vegetation present. Surface cover is limited.
Water deeper than one meter.
Scrub shrub: Wetland habitat dominated by low shrubs such as willow (Salix spp) or
hardhack (Spiraea douglasii).
Upland: Outside of the wetland boundary. Based on the lack of standing water and
wetland vegetation.
Wetland edge: Within 1m of standing water. Does not distinguish between terrestrial
and aquatic habitats. Used during fall 2008 and part of spring 2009
Wetland edge aquatic: within 1 m of the standing water in aquatic habitat.
Wetland edge no water: In fall 2008 this category was used to describe frogs that were
within the wetland boundary but utilizing terrestrial habitat. These frogs would be
classified as emergent terrestrial or wetland edge terrestrial in later years.
Wetland edge terrestrial: Within 1m of standing water in terrestrial habitat. Terrestrial
habitat could be within or outside the wetland boundary.
53
Appendix B: Dispersal of Frogs during telemetry.
Maps depict locations of frogs at the time telemetry transmitters were removed. For the fall of
2009 symbol shapes coincide with the release date. Frogs symbolized with a triangle were
released on October 29 and those with a circle were released on November 17.
54
55
56
57
Literature Cited.
Blaustein, Andrew R., and David B. Wake. 1990. "Declining amphibian populations: a
global phenomenon?" Trends in Ecology & Evolution 5, no. 7: 203.
Blaustein, Andrew R., David B. Wake, and Wayne P. Sousa. 1994. "Amphibian declines:
judging stability, persistence, and susceptibility of populations to local and global
extinction." Conservation Biology 8, no. 1: 60.
Blomquist, Sean M., and Malcolm L. Hunter Jr. 2010. "A Multi‐scale Assessment of
Amphibian Habitat Selection: Wood Frog Response to Timber Harvest."
Ecoscience 17, no.3: 251‐64.
Blouin, Michael S., Ivan C. Phillipsen, and Kirsten J. Monsen. 2010. "Population Structure
and Conservation Genetics of the Oregon Spotted Frog, Rana Pretiosa."
Conservation Genetics 11 no.6: 2179‐194.
Chelgren, Nathan D., Christopher A. Pearl, Michael J. Adams, and Jay Bowerman. 2008.
"Demography and Movement in a Relocated Population of Oregon Spotted Frogs
(Rana Pretiosa): Influence of Season and Gender." Copeia 2008 no.4: 742‐51.
Collins, James P., and Andrew Storfer. 2003. "Global amphibian declines: sorting the
hypotheses." Diversity & Distributions 9, no. 2: 89‐98.
Cushman K A, Pearl C A. 2007. A Conservation Assessment for the Oregon Spotted Frog
(Rana pretiosa). Portland, OR: USDA Forest Service Region 6, USDI Bureau of
Land Management, Oregon and Washington, Interagency Special Status and
Sensitive Species Program. Available at:
http://fresc.usgs.gov/products/papers/1578_Pearl.pdf, (accessed June 28, 2011)
58
Green, David M., Timothy F. Sharbel, Jennifer Kearsley, and Hinrich Kaiser. 1996
"Postglacial Range Fluctuation, Genetic Subdivision and Speciation in the
Western North American Spotted Frog Complex, Rana Pretiosa." Evolution 50
no.1: 374‐90.
International Union for Conservation of Nature (IUCN) “Amphibians on the IUCN Red
List” The IUCN Red List of Threatened Species.
http://www.iucnredlist.org/initiatives/amphibians (accessed June 11, 2011).
Johnson, Pieter T. J. 2006. "Amphibian diversity: Decimation by disease." Proceedings of
the National Academy of Sciences of the United States of America 103, no. 9:
3011‐3012
Kriger, Kerry M., and Jean‐Marc Hero. 2007. "The chytrid fungus Batrachochytrium
dendrobatidis is non‐randomly distributed across amphibian breeding habitats."
Diversity & Distributions 13, no. 6: 781‐788.
Lict, Lawrence 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: 613‐27.
Licht, L.E. 1986a. “Food and feeding behavior of sympatric red‐legged frogs, Rana
aurora, and spotted frogs, Rana pretiosa, in southwestern British Columbia.”
Canadian Field‐Naturalist 100:22‐31.
Licht, L.E. 1986b. “Comparative escape behavior of sympatric Rana aurora and Rana
pretiosa.” American Midland Naturalist 115:239‐247.
Lips, Karen R., Forrest Brem, Roberto Brenes, John D. Reeve, Ross A. Alford, Jamie
Voyles, Cynthia Carey, Lauren Livo, Allan P. Pessier, and James P. Collins. 2006.
"Emerging infectious disease and the loss of biodiversity in a Neotropical
59
amphibian community." Proceedings of the National Academy of Sciences of the
United States of America 103, no. 9: 3165‐3170.
Lips, Karen R, Jay Diffendorfer, Joseph R Mendelson, and Michael W Sears. 2008. "Riding
the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian
Declines." PLoS Biology 6, no. 3: e72.
Lynch, Jim 2006. Western Toad (Bufo Boreas) Habitat Use, Distribution, and
Conservation at Fort Lewis, Washington. M.E.S. Thesis. The Evergreen State
College,
McAllister, K. R. and W. P. Leonard. 1997. Washington State status report for the Oregon
Spotted Frog. Washington Department of Fish and Wildlife, Olympia,
Washington, USA.
McAllister, Kelly R., James W. Watson, Ken Risenhoover, and Tim McBride. 2004.
"Marking and Radio Telemtery of Oregon Spotted Frogs (Rana Pretiosa)."
Northwestern Naturalist 85 no.1: 20‐25.
Muths, Erin. 2003. "A Radio Transmitter Belt for Small Ranid Frogs." Herpetological
Review 34 no.4: 345‐48.
Padgett‐Flohr, Gretchen E., and Marc P. Hayes. 2011. "Assessment of the Vulnerability
of the Oregon Spotted Frog (Rana Pretiosa) to the Amphibian Chytrid Fungus
(Batrachochytrium Dendrobatidis)." Herpetological Conservation and Biology 6
no.2: 99‐106
Pearl, Christopher A., and Marc P. Hayes. 2002. "Predation by Oregon Spotted Frogs
(Rana Pretiosa) on Western Toads (Bufo Boreas) in Oregon." The American
Midland Naturalist 147 no.: 145‐52.
60
Pearl, Christopher. A, and Marc. P. Hayes. 2004. “Habitat associations of the Oregon
spotted frog (Rana pretiosa): A literature review.” Washington Department of
Fish and Wildlife, Olympia, WA, USA.
Pearl, Christopher A., Jay Bowerman, and Donnie Knight. 2005. "Feeding Behavior and
Aquatic Habitat Use by Oregon Spotted Frogs (Rana Pretiosa) in Central Oregon."
Northwestern Naturalist 86 no.1: 36‐38.
Pearl, Christopher A., Michael J. Adams, and Niels Leuthold. 2009. "Breeding Habitat and
Local Population Size of the Oregon Spotted Frog (Rana pretiosa) in Oregon,
USA." Northwestern Naturalist 90 no.2: 136‐47.
Richards, S.J., Sinsch, U., Alford, R.A. 1994. Radio Tracking. In: Measuring and
Monitoring Biological Diversity: Standard Methods for Amphibians, p. 155‐157.
Heyer,W.R., Donnelly, M.A., McDiarmid, R.W., Hayek,L.C., Foster, M.S., eds,
Washington, Smithsonian Institution Press.
Rollins‐Smith, Louise A., and J. Michael Conlon. 2005. "Antimicrobial peptide defenses
against chytridiomycosis, an emerging infectious disease of amphibian
populations." Developmental & Comparative Immunology 29, no. 7: 589‐598.
Rombough, Chris R., Marc P. Hayes, and J. D. Engler. 2006. "Rana Pretiosa (Oregon
Spotted Frog). Maximum Size." Herpetological Review 37 no.2: 210.
Rowley, Jodi J.L., and Ross A. Alford. 2007. "Techniques for Tracking Amphibians: The
Effects of Tag Attachment, and Harmonic Direction Finding versus Radio
Telemetry." Amphibia‐Reptilia 28 no.3: 367‐376.
Shovlain, Amie M. 2006. Oregon Spotted Frog (Rana pretiosa) Habitat Use and Herbage
(or Biomass) Removal from Grazing at Jack Creek, Klamath County, Oregon.
Masters in Science Thesis. Oregon State University.
61
USFWS (US Fish and Wildlife Service). 2010. Species assessment and listing priority
assessment form. Western Washington Fish and Wildlife Office, Lacey, WA.
Available at
http://ecos.fws.gov/docs/candidate/assessments/2010/r1/D02A_V01.pdf
Accessed June28, 2011
Washington Herp Atlas 2005. "Northern Red‐Legged Frog Key Features." Washington
Department of Natural Resources, 15 Feb. 2008.
http://www1.dnr.wa.gov/nhp/refdesk/herp/html/feat_raau.html. Accessed
June 11, 2011.
Watson, James W., Kelly R. McAllister, and D. John Pierce. 2003. "Home Ranges,
Movements, and Habitat Selection of Oregon Spotted Frogs (Rana Pretiosa)."
Journal of Herpetology 37 no.2: 292‐300.
White, Heather Q. 2002. Oviposition Habitat Enhancement and Population Estimates of
Oregon Spotted Frogs (Rana Pretiosa) at Beaver Creek, Washington. M.E.S
Thesis. The Evergreen State College.
Personal Communications
Andrea Gielens 2010 –Oregon spotted frog Husbandry Coordinator
Mountain View Conservation and Breeding Center
23898 Rawlison Crescent
Langley, British Columbia
Canada V1M 3R6
Jenifer Bohannon 2011‐ Wildlife Biologist
Washington department of Fish and Wildlife
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Natural Resources Building
1111 Washington St. SE
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