Spotted Frog Research Articles

A Successful Reintroduction of Columbia Spotted Frog (Rana luteiventris) through Repatriation of Recently Hatched Larvae

The Columbia Spotted Frog (Rana luteiventris; CSF) is widely distributed across northwestern North America; however, declines in the southernmost populations, including those in Utah, have resulted in the consideration of this species for protection under the Endangered Species Act. In 1998, a conservation agreement and strategy for Utah's populations of CSF was developed and identified needed conservation actions, including range expansion. We repatriated CSF larvae during 2008–2010 from an extant population in the Provo River into Beaver Creek, a beaver-dominated stream, in the Weber River, a watershed where contemporary surveys indicate CSF have likely been extirpated. In 2011, CSF breeding was first observed in the repatriated population when 11 egg masses were documented in four depositional areas. After ten years of monitoring egg mass numbers, we consider the repatriation a success as this population continues to grow and expand with a high of 54 egg masses (2019) within ten depositional areas (2020). High quality habitat and the large number of CSF larvae transplanted likely attributed to the success of this repatriation. We used 1–2 day old CSF larvae (Gosner life stage 20–21) as the repatriation life stage that we believed would be the most likely to prevent the spread of amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) from the known chytrid fungus positive donor site in the Provo River. Genetic testing of a robust sample (n = 59) of CSF tadpoles across the repatriation site in 2020 did not detect the presence of Bd, potentially indicating that we did not move Bd through the repatriation. Additional replicates would be required beyond this single experiment, however, to better determine if our transplant techniques are effective at preventing the spread of Bd.

Late-Season Movement and Habitat Use by Oregon Spotted Frog (Rana pretiosa) in a Large Reservoir in Oregon, USA

Dam-created reservoirs are common landscape features that can provide habitat for amphibians, but their water level fluctuations and nonnative predators can differ markedly from more natural habitats. We compared fall movement and habitat use by the Oregon Spotted Frog (Rana pretiosa) in the reservoir pool with nearby river and pond habitats at Crane Prairie Reservoir in central Oregon, USA. Movement rate of frogs in the river and ponds declined as water temperature cooled. Reservoir frogs moved further than those in the river or ponds, and their movement rate increased as water temperature cooled. Most frog locations across all site types were in aquatic herbaceous vegetation. We did not find shifts in habitat between early and late fall. Increased movement and the lack of habitat shift in our reservoir frogs deeper into fall contrast with R. pretiosa in non-reservoir sites in this study and others. Consistent use of vegetation by reservoir frogs throughout the fall could indicate cover use in presence of fish predators. Our study provides additional detail on the range of habitats used by R. pretiosa in fall and suggests areas for further work to improve survival in constructed sites with abundant fish predators.

The slow decline of a Columbia Spotted Frog population in Yellowstone National Park: A cautionary tale from a developed zone within a large protected area

Field research and surveys from the past century have provided a valuable resource for documenting amphibian population declines and investigating their possible causes. In Yellowstone National Park, research from the 1950s provided us with an extraordinary opportunity to investigate a Columbia Spotted Frog population’s decline over time in an area modified by increasing human occupation. Herpetologist F.B. Turner’s investigation (1953–1956) of a Columbia Spotted Frog (Rana luteiventris) population set the foundation for decades of study. In the 1990s, acting on Turner’s observation of an apparently sharp reduction in the number of frogs, we replicated his 1950s mark-recapture study with the goals of determining the extent of the decline and examining its possible causes. We continued annual monitoring through 2020. The population declined by nearly 80% between the mid-1950s and mid-1990s. The number of active breeding sites fell from 3 sites in 1950s, to 2 and then 1 in the 1990s, and none after 2007. The decline was accompanied by significant changes in the 28-hectare study area: a road constructed in the 1970s bisected the study area, headwater springs were developed, and facilities were built in and around the study area to support expanding human uses. Changes in spatial characteristics of the remnant frog population are thought to indicate the impacts of local habitat fragmentation, modification and loss. Here we focus on how the activity ranges and patterns of frog dispersal within the study area shrank to a zone upstream of the highway, prior to the eventual extirpation of the local breeding population. Multiple direct and indirect human-caused changes negatively influenced habitat that supported reproduction, survival, and recruitment. Climate change was not found to provide an adequate explanation of the observed changes. While a breeding population of Columbia Spotted Frogs has persisted next to the historical study area, it has experienced large fluctuations in egg mass production and repeated disease outbreaks in the last 15 years. This long-term case study provides a cautionary tale about shifting baselines and how land use may affect amphibian populations even in protected areas. We recommend extended monitoring for amphibians in developed zones of Yellowstone National Park, as visitation grows and conditions are further altered by infrastructure upgrades as well as by climate change.

Modelling physiological costs to assess impacts of climate change on amphibians in Yellowstone National Park, U.S.A

Amphibians are vital elements of ecosystems, serving as predator and prey. Their biphasic nature makes them dependent on aquatic and terrestrial habitats; as wet-skinned ectotherms, they are vulnerable to a range of environmental threats, including climate change. Yellowstone National Park (YNP) is becoming warmer and drier, and some wetlands important to amphibians have diminished. Continued climate change is predicted to reduce snowpack, soil moisture, and forest cover. We used data from models of future climate and vegetation cover to mechanistically model how climate change might affect the movements of Western Toads (Anaxyrus boreas) across the landscape of three test areas in YNP for the years 2050 and 2090, compared to 2000 as a baseline. Least-cost path analysis produced mixed results: for 2050 and 2090, physiological costs of movement increased in one test area and decreased in another; they were mixed in the third. These changes generally reflect the preference by toads for more open forests. Estimating costs for other species of YNP amphibians produced more negative results. For Columbia Spotted Frogs (Rana luteiventris) and Boreal Chorus Frogs (Pseudacris maculata) (both more aquatic and less adapted to terrestrial habitats), movement costs increased by about 2–15X. Reduced frequency or duration of rain events might limit the nocturnal movements of Western Tiger Salamanders (Ambystoma mavortium). Climate change may not have negative impacts on all amphibians throughout YNP, but increased movement costs for terrestrial habitats will accentuate effects of drying wetlands in at least parts of YNP. Land management actions that preserve habitat structure of both forest and low shrub cover may help mitigate continued drying conditions of climate change.

Amphibian population responses to mitigation: Relative importance of wetland age and design

Wetland creation is a common practice to mitigate for the loss of natural wetlands. However, there is still uncertainty about how effectively created wetlands replace habitat provided by natural wetlands. This uncertainty is due in part because post-construction monitoring of biological communities, and vertebrates especially, is rare and typically short-term (<5 years). We estimated occupancy of 4 amphibian species in 8 created mitigation wetlands, 7 impacted wetlands, and 7 reference wetlands in the Greater Yellowstone Ecosystem in Wyoming, USA. Mitigation wetlands were created to replace wetland habitat that was lost during road construction and ranged in age from 1 to 10 years when sampled. Impacted wetlands were natural wetlands partially filled by road construction and were adjacent to a highway. We sampled for amphibian larvae during 6 summers from 2013 to 2020 and used multi-species occupancy models that estimated detection and occupancy of each of 4 amphibian species to determine how amphibian responses changed over time, especially in mitigation wetlands. Occupancy did not differ between impacted and reference wetlands for any of the 4 amphibian species. Western Toads (Anaxyrus boreas) were most common (although briefly) in created wetlands, and occupancy of Columbia Spotted Frogs (Rana luteiventris), Western Tiger Salamanders (Ambystoma mavortium), and Boreal Chorus Frogs (Pseudacris maculata) was lower in created wetlands than in impacted or reference wetlands. Individual wetland area was positively associated with occupancy for all 4 species and wetland vegetation cover was positively associated with Boreal Chorus Frog and Columbia Spotted Frog occupancy; these results emphasize the importance of design characteristics when planning mitigation wetlands. The link between wetland age and occupancy was complex and included threshold and quadratic relationships for three of the four species, but only Boreal Chorus Frog occupancy was still increasing slowly at the end of our study. Our results indicate created wetlands did not attain the suitability of impacted and natural wetlands for local amphibians, even several years after construction. The complex relationships between wetland age and species-specific occupancy illustrate the importance of long-term monitoring in describing population responses to the construction of wetlands as mitigation for wetland loss.

ACTIVE SEASON AND PRE-OVERWINTERING MICROHABITAT USE BY OREGON SPOTTED FROGS (RANA PRETIOSA) AND AMERICAN BULLFROGS (LITHOBATES CATESBEIANUS [RANA CATESBEIANA]) AT CONBOY LAKE NATIONAL WILDLIFE REFUGE, WASHINGTON

Conboy Lake National Wildlife Refuge (CLNWR) in Washington State supports one of the largest remaining populations of federally listed Oregon Spotted Frogs (OSF; Rana pretiosa). Invasive American Bullfrogs (Lithobates catesbeianus [Rana catesbeiana]), implicated in amphibian declines, are also abundant at CLNWR. Owing to the likely negative effect of this aquatic invader on the highly aquatic OSF, bullfrog control strategies are needed. One method is to limit habitat used by bullfrogs while retaining or enhancing OSF habitat, but for such an approach to be implemented, the 2 species must partition habitat sufficiently. We used radiotelemetry to characterize OSF and bullfrog active-season and pre-overwintering habitat in the human-engineered ditch system at CLNWR. We tracked 12 OSF and 10 bullfrogs from mid-to-late summer, recorded data on frog location and habitat, and analyzed movement patterns, niche breadth, and spatial differences between species. Based on minimum convex polygons, bullfrogs overlapped extensively with OSF habitat space in the ditch system. During the active season, niche analyses also showed extensive overlap in the species' vegetation associations, with selected exceptions at the microhabitat scale. However, each species used distinct pre-overwintering habitats. The small differences in active-season microhabitats and pre-overwintering habitats, and our relatively narrow study conditions, create uncertainty about these species' habitat use in a broader context. Nonetheless, these results underscore the challenge of managing an invasive species that is both a habitat generalist and congener and expose the need for further research to guide management approaches to favor OSFs at CLNWR.

HERPETOLOGICAL INVENTORY OF THE STIKINE RIVER REGION, ALASKA, 2010–2018

We conducted 7 y of herpetological inventories in the Stikine River Region of Southeast Alaska between 2010 and 2018. We observed a total of 2555 individuals representing 6 amphibian species in 5 families at more than 30 sites. This study did not document any reptiles. Among sampled sites, Shakes Hot Springs and Twin Lakes Warm Springs exhibited the greatest density of amphibians across all study years, and both served as breeding habitat for 1 or more species. The Twin Lakes, Shakes Hot Springs, and Paradise Slough sites exhibited the greatest species diversity, with 4 amphibian species recorded at each site. We also compared occurrence and breeding activity to historical data to elucidate possible changes in site-specific assemblages over time. We report new distribution records for the Long-toed Salamander (Ambystoma macrodactylum), and confirmed recent presence of this species at Twin Lakes, where it was thought to have been extirpated. We also confirm the presence of Columbia Spotted Frogs (Rana luteiventris) on Wrangell Island. We were unable to verify the presence of the Northwestern Salamander (Ambystoma gracile) or the Common Gartersnake (Thamnophis sirtalis) in this region. The observations reported here provide baseline amphibian population data for comparison with future surveys.

Late-Season Movement and Habitat Use by Oregon Spotted Frog (Rana pretiosa) in Oregon, USA

Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. Distinctive features like springs or semi-terrestrial retreats can host m...

Discovery of the Oregon Spotted Frog in the Northern Puget Sound Basin, Washington State

The Oregon Spotted Frog (Rana pretiosa), a federally threatened species also listed as endangered in Washington State, has a historical distribution that extends from southwestern British Columbia to northeastern California, yet their current range appears highly fragmented. This pattern may reflect this species' distinctive aquatic habitat requirements or simply be a function of the limited historical survey effort in selected areas. Hence, in an attempt to determine whether any additional populations of Oregon Spotted Frogs existed in the northern Puget Sound basin of Washington State, we conducted surveys at a large number of sites (n = 131) across this region in 2011–2013. To increase the likelihood of detecting this species, we created a Geographic Information System screening tool to identify areas of appropriate habitat (low stature emergent marsh ≥4 ha) based on National Wetlands Inventory maps. We also concentrated survey efforts on the headwater portions of lowland streams because non-headwater areas within the study area are highly altered and more likely to harbor exotic aquatic predators (American Bullfrogs [Lithobates catesbeianus] and warmwater fish species), which reduce the likelihood of Oregon Spotted Frog occupancy. We visually documented breeding activity of Oregon Spotted Frogs at 13 previously unrecognized sites in the Samish (n = 8), Nooksack (n = 4), and Sumas (n = 1) watersheds. We located a total of 1359 Oregon Spotted Frog egg masses at the 13 occupied sites over the three survey seasons. We genetically verified the species identification at 4 of these sites. In the course of these surveys, we also documented breeding chronology and provided information on habitat. Vegetation changes due to cessation of grazing and recent woody plantings may have decreased habitat suitability in at least 5 of the 13 occupied sites. Despite time and land-ownership constraints, our discovery of new breeding sites suggests that additional surveys for Oregon Spotted Frogs are needed to fully understand the species' distribution. Although Oregon Spotted Frogs are still rare, their current distribution is more widespread than previously recognized.

Plains Spadefoot,Spea bombifrons, Confirmed in Yellowstone National Park

Established by an act of Congress in 1872, Yellowstone National Park (YNP) encompasses 8983 km of temperate zone habitat and contains a wide array of plant, animal, and microbial species. Although YNP contains almost 400 species of animals, it is not considered to have high amphibian diversity. There are 4 amphibian species known in the park: Boreal Chorus Frog (Pseudacris maculata); Columbia Spotted Frog (Rana luteiventris); Western Toad (Anaxyrus boreas); and Western Tiger Salamander (Ambystoma mavortium). The Northern Leopard Frog (Lithobates pipiens) is believed to be regionally extinct in YNP and Grand Teton National Park because the species has not been documented since the 1950s (Koch and Peterson 1995). Yellowstone National Park and its fauna have long been the focus of researchers from around the globe, but the discovery of a previously undocumented vertebrate happens infrequently. However, in 2014, a breeding population of Plains Spadefoot (Spea bombifrons) was confirmed in YNP (Fig.1). Prior to this discovery, 1 of the 2 Spea species (S. bombifrons or S. intermontana) that naturally occur in the states surrounding YNP (Wyoming, Montana, and Idaho) was reported in 1982 downstream of Fairy Falls on the west side of the park (Koch and Peterson 1995). The Plains Spadefoot has likely been present in YNP, but has gone undetected because of its fossorial lifestyle and limited distribution. Here, we describe our discovery of the Plains Spadefoot in YNP, the genetic analysis used to identify the species, and the characteristics of the breeding site. In the summer of 2013, a recently metamorphosed spadefoot was observed in an ephemeral pool in the Lower Geyser Basin east of Fairy Creek in YNP at an elevation of 2201 m. The identity of the species could not be confirmed because of morphological similarities between 2 spadefoot species (S. bombifrons and S. intermontana) that occur in the region, and the lack of prominent features in juveniles (Hall 1998; Behler and King 2005; Dodd 2013). The presence of a metamorph suggested that a breeding site was nearby, and the area was surveyed the following spring. Spadefoots were heard calling on the night of 20 May 2014, and 16 male spadefoots were captured on the night of 21 May 2014. Calls were heard until 25 May 2014, and spadefoot tadpoles were observed at the site shortly after the breeding season ended. The 2 species of spadefoots occur in 4 counties (Park Co., WY; Teton Co., WY; Park Co., MT; Gallatin Co., MT) that border and extend into YNP (Fig 2). These species are morphologically similar, with the size and texture of the hump between the eyes being the main distinguishing characteristic (Behler and King 2005). Therefore, tissue samples from 8 spadefoot tadpoles and 1 adult were sent to Pisces Molecular (Boulder, Colorado) for species identification using genetic analyses. Total DNA was extracted from all samples and amplified using polymerase chain reaction (PCR) to target a 407 base-pair segment of the mitochondrial Cytochrome Oxidase 1 (COX1) gene. For each sample, the sequence of both strands of the amplified fragment was determined using Sanger sequencing (BigDye v3.1, Life Technologies, Carlsbad, California) and an ABI 3130 Genetic Analyzer. The double strand sequence for each sample was aligned with each other and compared with the COX1 sequences for S. bombifrons and with S. intermontana COX1 regions from the BOLD Systems public database (accession numbers EANAA248-12 and EANAA119-12, respectively; http://www.bold systems.org/). The 9 sample COX1 amplicon sequences from the YNP spadefoots were completely identical, which indicated they were from the same species. When the consensus GENERAL NOTES

Characterization of Springtime Coliform Populations at the End Creek Wetland Restoration (Union Co., Oregon, USA): A Three-Year Study

In 2005, a 550-acre tract of agricultural land containing two small streams near La Grande, Oregon was registered in the U.S. Federal Wetlands Reserve Program. This designation was part of a plan to reclaim and restore the wetland to its natural state. Initial efforts at the End Creek Restoration Project restored both End Creek and South Fork Willow Creek to a natural course through rechanneling, and several plantings had restored some of the native flora. Since its establishment, the End Creek streams and floodplain have become a reserve for summer steelhead (Oncorhynchus mykiss), a threatened anadromous salmonid, and many migratory birds. The threatened Columbia Spotted Frog has also established itself in some of the ponds. As part of an effort to establish a baseline for water quality, we monitored total springtime coliform and fecal coliform bacteria in three of the End Creek ponds for three years. The results of this study indicate that, throughout any given spring, the numbers of both coliform and fecal coliform bacteria can fluctuate markedly among ponds on any given day, and that in any particular pond the numbers fluctuate from week to week. In addition, our analysis suggests that in early spring, the numbers of these organisms also fluctuate from year to year. The causes of these fluctuations are not well understood, but are expected to reflect both springtime flooding and the migrations of source animals such as waterfowl and cervids. Information gathered from this study will help inform future management activities on the wetland.

Interpopulation Variability in Evasive Behavior in the Oregon Spotted Frog (Rana pretiosa)

Few data exist that quantify evasive behavior in postmetamorphic anurans. On the basis of our casual observations that Oregon Spotted Frogs (Rana pretiosa) from one of two different populations appeared to exhibit a more pronounced evasive response, we used a pseudopredator stimulus to quantify the evasive response of juveniles from the two populations. We drew test animals from a pool of animals for each population that were captive-reared under identical conditions. Using latency to initial response, we compared the distribution of response times between the two populations at two sequential intervals over the rearing period. In both experiments, the Conboy Lake population had shorter latency-to-response times than the Black River population. However, we also found that latency-to-response times were shorter during the second test interval than during the first test interval for each population. The basis of population differences in response times may reside in differences in the predator set influencing each population, contaminants differentially influencing the Black River population in a negative manner, or some combination of both. Explanation for the faster latency-to-response times in the second experiment is unclear since both maturation and the length of the captive rearing interval may contribute to the effect, but they are confounded in this study.

Occurrence of Amphibians in British Columbia North of 57°N

The Long-toed Salamander, Western Toad, Boreal Chorus Frog, Columbia Spotted Frog, and Wood Frog are known to occur in British Columbia north of 57°N, a remote region that has received only sparse attention with regard to amphibian surveys. It is unclear whether range limits and gaps in the ranges of species reflect the actual absence of a particular species, or are due to an absence of data. To assess this state of affairs, published and unpublished data from several sources, including my own surveys and incidental observations submitted to me by others, were compiled to more fully understand the ranges of amphibians in northern British Columbia.

Effects of Rotenone on Columbia Spotted Frogs Rana luteiventris during Field Applications in Lentic Habitats of Southwestern Montana

AbstractFisheries managers are restoring native populations by removing nonnative fishes worldwide. Increasingly, the piscicide rotenone is used to accomplish this. Fish introductions and removals change the aquatic environment, and it is important to consider the impacts of these actions on nontarget species, including amphibians. Laboratory experiments have shown that rotenone can negatively affect tadpoles. We therefore assessed the effects of rotenone used on two wild amphibian populations. The commercial piscicide formulation CFT Legumine (5% rotenone) was applied at 1 mg/L (50 μg/L rotenone) to a lake containing nonnative trout in Yellowstone National Park (YNP) in 2006 and two fishless wetlands on private lands in southwestern Montana in 2008. Amphibian surveys were conducted immediately prior to and after the rotenone treatments to obtain tadpole population estimates. Follow‐up surveys were conducted 1 year posttreatment to estimate tadpole recovery. In YNP, additional surveys were conducted 2 and 3 years postapplication to observe longer‐term effects of fish removal and the subsequent introduction of native fish. Within 24 h following application of rotenone, there was 100% mortality in gill‐breathing tadpoles, but nongill‐breathing metamorphs, juveniles, and adults were apparently unaffected. In the years following, tadpoles repopulated all waters and population levels were similar to, or, in the case of YNP because of concurrent fish removal, higher than pretreatment levels. In YNP, tadpole abundance and distribution decreased after westslope cutthroat trout Oncorhynchus clarkii lewisi were stocked in the treated lake.Received October 22, 2011; accepted May 4, 2012

Toxicity of the Piscicide Rotenone to Columbia Spotted Frog and Boreal Toad Tadpoles

AbstractThe piscicide rotenone is commonly used to remove nonnative fishes from natural aquatic systems. While the effects of rotenone on fish are well documented, the effects of this chemical on amphibians are less well known. We determined the toxicity of the rotenone formulation CFT Legumine (5% rotenone) to three ages—Gosner age ranges 21–25, 30–35, and 40–45—of tadpoles of the Columbia spotted frog Rana luteiventris and the boreal toad Anaxyrus boreas under laboratory conditions. Tadpoles of both species were exposed to 0.1, 0.5, and 1.0 mg/L CFT Legumine (0.005, 0.025, and 0.050 mg/L rotenone, respectively) in static, 96‐h exposure trials; surviving individuals were placed in rotenone‐free water and raised until metamorphosis. In an additional experiment, Columbia spotted frog tadpoles were exposed to 1.0 mg/L CFT Legumine for 1, 2, 3, or 4 h before being placed in rotenone‐free water for the duration of a 96‐h exposure period. Tadpole mortality increased with increases in CFT Legumine concentration and exposure period. Individuals exposed to 1.0 mg/L of product experienced significantly greater mortality than did control tadpoles (P &lt; 0.001), with 99–100% mortality occurring in the youngest age‐group (Gosner 21–25) in both species. In Columbia spotted frog tadpoles, mortality decreased as age increased, while age did not affect mortality in boreal toad tadpoles. Rotenone produced no biologically significant effects on growth or metamorphosis. Our findings suggest that the use of 1.0 mg/L CFT Legumine to remove nonnative fish may cause significant mortality to larval amphibians if they are exposed for 96 h; exposures to lower dosages (0.5 mg/L of product) or for shorter durations (≤4 h), however, resulted in less mortality. Fisheries managers can use these results to improve amphibian conservation in fish restoration areas and reduce the impacts on larval amphibian populations.

Ability of Oregon Spotted Frog (Rana pretiosa) Embryos from Central Oregon to Tolerate Low Temperatures

minima, egg mass, oviposition More than half of the known remaining populations of the Oregon Spotted Frog (Rana pretiosa) are at elevations .1200 m along the Cascade Range and its eastern flank in Oregon (Pearl and Hayes 2005). Rana pretiosa in this region typically breed soon after thaw and often lay eggs in water ,20 cm deep (Pearl and others 2009). Egg masses in shallow microhabitats experience broad temperature fluctuations, and ice formation on the surface is common (Bull and Shepherd 2003). At .20 oviposition sites around Sunriver in central Oregon (elevation 1270 m), we have observed high survival of R. pretiosa embryos after exposure to subfreezing air temperatures and ice cover for up to several days. These observations and the characteristics of oviposition sites across much of the species’ range along the Cascade Range suggest that R. pretiosa eggs in this region may be more tolerant of low temperatures than previously reported. Information on thermal limits of R. pretiosa embryos derives from studies of 1 population in the Fraser River Valley of southwestern British Columbia. The low elevation of this site (approximately 50 m above sea level) and its proximity to the Strait of Georgia and Pacific Ocean make its climate more moderate than much of the extant range of R. pretiosa. Licht (1971) reported a lethal minimum, the temperature at which egg survival is ,50%, near 66C for eggs from that site at a range of stable temperature treatments in the laboratory. A subset of embryos survived lower temperatures for up to 8 h, after which trials were terminated (Licht 1971), but data were not presented on presence or timing of develop

Submerged Calling by Oregon Spotted Frogs (Rana pretiosa) Remote from Breeding Aggregations

Submerged Calling by Oregon Spotted Frogs (Rana pretiosa) Remote from Breeding Aggregations

Sexual Selection on Morphology in an Explosive Breeding Amphibian, the Columbia Spotted Frog (Rana luteiventris)

It is well documented that sexual selection acts on morphological differences between individuals and can lead to sexual dimorphism in species with male combat and female choice. However, the effect of sexual selection on the evolution of morphological traits is poorly understood in species with scramble competition in which males race for access to females during a brief pulse of breeding activity. Because male access to females may be more random in scramble mating systems, male morphological traits may not strongly influence mating success. To investigate the influence of sexual selection on male morphology in a species with a scramble mating system, we collected detailed morphological measurements from male and female Columbia Spotted Frogs (Rana luteiventris), which have an extreme scramble mating system. Male Columbia Spotted Frogs have enlarged thumb (nuptial) pads and muscular forearms, which may help them grasp females. As predicted, we discovered that males found in amplexus with females had proportionately larger nuptial pads and thicker forearms than did unpaired males, but mating success was not related to overall body size. Although many single males attempted to dislodge males already in amplexus with females, no attempted takeovers were successful. Therefore, we suggest that the advantage of thick forearms and large nuptial pads occurs during the initial phase of securing a female when she first enters the breeding area. These findings suggest that sexual selection may influence morphology even in a species with scramble mating.

Short-Term Effect of Cattle Exclosures on Columbia Spotted Frog (Rana luteiventris) Populations and Habitat in Northeastern Oregon

Livestock grazing is a common land use across the western United States, but concerns have been raised regarding its potential to affect amphibian populations. We studied the short-term effects of full and partial livestock grazing exclosures on Rana luteiventris (Columbia Spotted Frog) populations using a controlled manipulative field experiment with pre- and posttreatment data (2002-2006). Despite a significant increase in vegetation height within grazing exclosures, we did not find treatment effects for egg mass counts, larval survival, or size at metamorphosis 1-2 years following grazing exclosure installation. Water samples taken in late summer showed concentrations of nitrite, nitrate, ammonia, and orthophosphate that were low or near detection limits across all ponds and years. The results of this experiment do not support a hypothesis that limiting cattle access to breeding ponds will help conserve R. luteiventris populations in our study area. Further research is needed to evaluate regional variation and long-term effects of grazing exclosures on R. luteiventris populations.

Demography and Movement in a Relocated Population of Oregon Spotted Frogs (Rana pretiosa): Influence of Season and Gender

We used five years of recapture data and Bayesian estimation to assess seasonal survival, movement, and growth of Oregon Spotted Frogs (Rana pretiosa) relocated into created ponds at Dilman Meadow in Oregon, USA. We evaluate hypotheses specific to the relocation and elucidate aspects of R. pretiosa life history that are poorly known. The odds of survival of relocated individuals during the first year following relocation were 0.36 times the survival odds of relocated and non-relocated frogs after one year since the relocation. Survival rate was higher for large frogs. After accounting for frog size, we found little variation in survival between ponds at Dilman Meadow. Survival was lowest for males during the breeding/post-breeding redistribution period, suggesting a high cost of breeding for males. The highest survival rates occurred during winter for both genders, and one small spring was used heavily during winter but was used rarely during the rest of the year. Individual growth was higher in ponds that were not used for breeding, and increased with increasing pond age. Our study supports other evidence that R. pretiosa use different habitats seasonally and are specific in their overwintering habitat requirements. Because frogs were concentrated during winter, predator-free overwintering springs are likely to be of particular value for R. pretiosa populations.