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News & Stories Trout, beavers, droughts, and 'precious' frog
Authors: Christopher A Pearl; Rachel Powers
March 25, 2025
The Oregon spotted frog’s scientific name is Rana pretiosa, which translates to “precious frog” in Latin. Precious things are often rare, which is the case with the Oregon spotted frog across parts of its range. It was listed as threatened under the Endangered Species Act in 2014. Although several threats are responsible for the Oregon spotted frog’s decline, loss of the wetland habitat it needs to survive is at the top of the list. The U.S. Fish and Wildlife Service’s national report on wetlands status and trends reveals nationwide losses. In the Klamath Basin of Oregon and California, it’s estimated that 50-90% of the Oregon spotted frog’s wetland habitat has been lost due to habitat modification and prolonged drought.
U.S. Geological Survey scientists are working with other federal agencies, non-profit organizations, and private landowners to research the effectiveness of restoration projects for multiple species and aid in the recovery of the Oregon spotted frog.
“As landowners working to benefit wildlife, livestock, ecosystem health and water quality, partnering with scientists to research the Oregon spotted frog is a vital piece of our restoration ranching approach,” says Alex Froom, owner of a ranch on the Wood River in Oregon. Restoration work on their ranch includes removing invasive bullfrogs and improving habitat for Oregon spotted frogs.
The non-profit Trout Unlimited, whose work in the Klamath Basin is focused on restoring healthy ecosystems for fisheries, amphibians, and other aquatic species, is a key partner working closely with USGS. Several of the strategies being deployed on federally managed land and private ranches are aimed at improving the drought resilience of aquatic habitats, benefiting a wide range of species.
Historically, the range of the Oregon spotted frog overlapped with that of the North American beaver. Beaver numbers in the Pacific Northwest declined dramatically due to the fur trade in the late 1700s and early 1800’s, as did the ecosystem services they provide. Beaver dams and associated ponds retain water in landscapes that otherwise would not hold it. Warmer water along pond edges promotes development of frog eggs and tadpoles and provides adult frogs with feeding and basking areas. Radio telemetry studies suggest Oregon spotted frogs use other beaver-created features like channels and dams as shelter during the winter. Mimicking these features, or enhancing remnant channels and dams, are possible solutions for improving water retention, increasing shelter opportunities and providing additional habitat.
USGS monitoring of Oregon spotted frog populations is showing early signs of success with these types of projects.
In the longest running study of its kind in the Klamath, USGS researchers counted Oregon spotted frog egg masses and adults along Jack Creek on U.S. Forest Service and private land. Surveys were done at reference sites with no habitat modifications, sites where old beaver ponds were excavated and deepened, and sites that were excavated but had no remnant beaver ponds.
Thirteen years of annual sampling revealed that survival of adult Oregon spotted frogs was almost 20% higher at reaches with excavated remnant beaver ponds compared to reference sites. Satellite images revealed that vegetation at restored sites stayed green later into the summer- an indicator of improved water retention. One promising clue that restoration of this type can work was the fact that frog breeding was concentrated in two excavated beaver ponds relative to other sites.
At a site on Crane Creek, USGS scientists partnered with the U.S. Fish and Wildlife Service, Trout Unlimited, and the owner of the Sevenmile Ranch to collect Oregon spotted frogs prior to stream and riparian restoration. Restoration work included redirecting water from a canal back into historical creek meanders and creating a series of ponds. Once restoration was complete, researchers released the frogs and monitored where they went and where they chose to lay eggs. Numbers of egg masses and adults increased in restored areas, indicating modifications to the habitat were favorable for breeding success and survival.
“So far, we’ve seen a noticeable response from Oregon spotted frogs at one site, a smaller but still positive response at another site, and it’s still too early to tell how frogs will respond at two other sites,” says Christopher Pearl, wildlife biologist at the USGS Forest and Rangeland Ecosystem Science Center in Corvallis, Oregon. “The signs are encouraging, and we’re also learning a lot about habitat requirements and behavior of Oregon spotted frogs that will help our partners plan future restoration projects.”
That knowledge about how Oregon spotted frogs respond to habitat modifications is directly used for restoration and recovery planning. The U.S. Fish and Wildlife Service is responsible for assessing the recovery of threatened species and reevaluating listing under the Endangered Species Act.
“We’ve been working in partnership with the USGS for over two decades on all aspects of Oregon spotted frog conservation and recovery,” says Jennifer O’Reilly, biologist with the U.S. Fish and Wildlife Service and Oregon spotted frog species lead. “USGS has a strong understanding of the Service’s role in implementing the Endangered Species Act and has contributed research that’s crucial to our decision making.”
North American beaver populations are slowly recovering in the Pacific Northwest, and USGS is working with partners to study how Oregon spotted frogs respond to the arrival of beavers and newly constructed dams and ponds. Human-led wetland restoration is generating results now, but beaver may lead the way in the future. Either way, USGS scientists will be there to document the Oregon spotted frog’s recovery.
Papers & Reports Bayesian networks facilitate updating of species distribution and habitat suitability models
Authors: Adam Duarte; Robert S Spaan; James T Peterson; Christopher A Pearl; Michael J Adams
Date: 2024-12-06 | Outlet: Ecological Modelling
Managers often rely on predictions of species distributions and habitat suitability to inform conservation and management decisions. Although numerous approaches are available to develop models to make these predictions, few approaches exist to update existing models as new data accumulate. There is a need for updatable models to ensure good modeling practices in an aim to keep pace with change in the environment and change in data availability to continue to use the best-available science to inform decisions. We demonstrated a workflow to deliver predictive models to user groups within Bayesian networks, allowing models to be used to make predictions across new sites and to be easily updated with new data. To demonstrate this workflow, we focus on species distribution and habitat suitability models given their importance to informing conservation strategies across the globe. In particular, we followed a standard process of collating species encounter data available in online databases and ancillary covariate data to develop a habitat suitability model. We then used this model to parameterize a Bayesian network and updated the model with new data to predict species presence in a new focal ecoregion. We found the network updated relatively quickly as new data were incorporated, and the overall error rate generally decreased with each model update. Our approach allows for the formal incorporation of new data into predictions to help ensure model predictions are based on all relevant data available, regardless of whether they were collected after initial model development. Although our focus is on species distribution and habitat suitability models to inform conservation efforts, the workflow we describe herein can easily be applied to any use case where model uncertainty reduction and increased model prediction accuracy are desired via model updating as new data become available. Thus, our paper describes a generalizable workflow to implement model updating, which is widely recognized as a good modeling practice but is also underutilized in applied ecology.
Data Release Mercury concentrations in amphibian tissues across the United States, 2016-2021
Authors: Colleen S Emery; Collin A Eagles-Smith; Kelly L Smalling; Blake R Hossack; Brian J Tornabene; Michael J Adams; Adam R Backlin; Adrianne B Brand; Robert N Fisher; Jill Fleming; Brad M Glorioso; Daniel A Grear; Evan HC Grant; Brian J Halstead; Patrick M Kleeman; David AW Miller; Erin Muths; Christopher A Pearl; Jennifer C Rowe; Caitlin T Rumrill; Hardin J Waddle; Megan E Winzeler
Date: 2023-08-23
Comma-separated values (.csv) file containing data related to amphibian sampling across the United States between 2016 and 2021. Data files contain mercury concentrations in amphibian and dragonfly tissues, mercury concentrations in sediment, as well as amphibian morphometrics, and habitat and climate characteristics where the samples were collected.
Papers & Reports Adjacent and downstream effects of forest harvest on the distribution and abundance of larval headwater stream amphibians in the Oregon Coast Range
Authors: Adam Duarte; Nathan D Chelgren; Jennifer C Rowe; Christopher A Pearl; Sherri L. Johnson; Michael J Adams
Date: 2023-07-21 | Outlet: Forest Ecology and Management
Forest harvest is a primary landscape-scale management action affecting riparian forests. Although concerns about impacts of forest harvest on stream amphibians is generally limited to areas adjacent to harvest, there is a paucity of information regarding potential downstream effects of forest harvest on these species. We designed a before-after, control-impact (BACI) experiment to quantify potential impacts of clearcut logging that included 12-m buffers or smaller variable-width buffers on the distribution and abundance of headwater stream amphibians in adjacent and downstream areas. We sampled larval coastal tailed frogs (Ascaphus truei), coastal giant salamanders (Dicamptodon tenebrosus), and Columbia torrent salamanders (Rhyacotriton kezeri) across 3,915 sampling occasions that spanned 13 study reaches in 2008–2011 (pre-harvest) and 2013–2016 (post-harvest) as part of the Trask River Watershed Study in the Oregon Coast Range, U.S.A. We analyzed these data using occupancy models to estimate occupancy and (when possible) relative abundance, while accounting for various sources of imperfect detection. All species exhibited reduced occupancy adjacent to clearcuts with variable-width buffers (odds ratios [ORs] ranged = 0.24–0.48), and these negative impacts were not always diminished when increasing the buffer size to 12 m (ORs ranged = 0.20–3.56). Dicamptodon tenebrosus was the only species to have occupancy impacted in downstream areas, and this negative impact was related to clearcut logging with uniform 12-m buffers (OR = 0.60). This species was also the only species to have abundance negatively impacted by forest harvest in downstream areas (OR = https://0.41 with uniform 12-m buffers, OR = https://0.38 with variable-width buffers), albeit impacts to abundance were not evaluated for R. kezeri. Ascaphus truei abundance increased in areas downstream of clearcut logging with uniform 12-m buffers (OR = 2.92). Although we found the direction and magnitude of responses varied by species, our study confirms that clearcut logging can have negative impacts on amphibians that inhabit the adjacent stream areas. Perhaps more importantly, we also found that forest harvest can have negative effects on stream amphibians downstream of the harvested area and that increasing the buffer size to 12 m did not necessarily diminish these impacts in adjacent and downstream areas. Altogether, our study provides a nuanced picture of adjacent and downstream effects of forest harvest on three endemic headwater stream amphibians, and our findings demonstrate that forest management practices should consider downstream effects on aquatic taxa when assessing the impact of harvesting trees near headwater streams.
Papers & Reports Broad-scale Assessment of Methylmercury in Adult Amphibians
Authors: Brian J Tornabene; Blake R Hossack; Brian J Halstead; Collin A Eagles-Smith; Michael J Adams; Adam R Backlin; Adrianne B Brand; Colleen S Emery; Robert N Fisher; Jill Fleming; Brad M Glorioso; Daniel A Grear; Evan HC Grant; Patrick M Kleeman; David AW Miller; Erin Muths; Christopher A Pearl; Jennifer C Rowe; Caitlin T Rumrill; Hardin J Waddle; Megan E Winzeler; Kelly L Smalling
Date: 2023-10-30 | Outlet: Environmental Science & Technology
Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats, including contaminants. While the bi-phasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used non-lethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ? 0.67) whereas total Hg in sediment was not (R2 ? 0.04). Our study, the largest broadscale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for non-lethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify potential threats of MeHg to amphibians.
Papers & Reports Broad-scale assessment of methylmercury in adult amphibians
Authors: Brian J Tornabene; Blake R Hossack; Brian J Halstead; Collin A Eagles-Smith; Michael J Adams; Adam R Backlin; Adrianne B Brand; C S Emery; Robert N Fisher; Jill Fleming; Brad M Glorioso; Daniel A Grear; Evan HC Grant; Patrick M Kleeman; David AW Miller; Erin Muths; Christopher A Pearl; Jennifer C Rowe; Caitlin T Rumrill; Hardin J Waddle; Megan E Winzeler; Kelly L Smalling
Date: 2023-10-30 | Outlet: Environmental Science and Technology 57:17511-17521
Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats including contaminants. While the biphasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used nonlethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether the concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ? 0.67), whereas total Hg in sediment was not (R2 ? 0.04). Our study, the largest broad-scale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for nonlethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify the potential threats of MeHg to amphibians.
Data Release Cascade torrent salamander (Rhyacotriton cascadae) surveys in Oregon and Washington 2022
Authors: Jennifer C Rowe; Christopher A Pearl; Brome McCreary; Meredith S Diskin; Chelsea Waddell; Michael J Adams
Date: 2023-04-04
We conducted visual surveys for (Rhyacotriton cascadae at 65 sites in Oregon and Washington that were historically occupied by the species to evaluate it's status across it's range and determine whether the species merits listing under the Endangered Species Act. This dataset includes counts of all amphibians observed during each site survey, as well as habitat and water sampling covariates between 4 May and 12 October of 2022.
Data Release Oregon spotted frog (Rana pretiosa) telemetry and habitat use at Crane Prairie Reservoir in Oregon, USA
Authors: Christopher A Pearl; Jennifer C Rowe; Brome McCreary; Michael J Adams
Date: 2022-04-06
We used radio-telemetry to study late-season movement and habitat use by Oregon spotted frogs (Rana pretiosa) at Crane Prairie Reservoir in Oregon. This dataset includes individual frog location data and habitat use during each tracking event that occurred roughly weekly between September and late November of 2018.
Papers & Reports Population Dynamics of the Threatened Oregon Spotted Frog (Rana pretiosa) Before and After Drought Mitigation
Authors: Jennifer C Rowe; Christopher A Pearl; Adam Duarte; Brome McCreary; Michael J Adams
Date: 2023-09-22 | Outlet: The Journal of Wildlife Management
Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs (Rana pretiosa) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers (Castor canadensis[/]), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought.
News & Stories Update to annotated bibliography of grazing effects on amphibians and their habitats
Authors: Jennifer C Rowe; Christopher A Pearl; Michael J Adams; Brome McCreary; Meredith S Diskin
February 14, 2022
USGS researchers recently published an update to the 2020 ‘Annotated bibliography of grazing effects on amphibians and their habitats’ data release, a global synthesis of literature pertaining to livestock grazing effects on amphibians and their habitats. The update includes an additional 10 grazing-related publications that were released between 2020 and 2021. The data release features an interactive search tool, which has also been updated. Users of the annotated bibliography search tool can query records by user-defined criteria and output results in report format. This tool aids users in synthesizing research related to a range of specific questions and should assist land managers in evaluating and implementing grazing while maintaining habitat for wetland amphibians.
You can access the updated search tool here: https://doi.org/10.5066/P9GGPPF7
Data Release Capture-mark-recapture data for Oregon spotted frogs [Rana pretiosa] along the Deschutes River, Oregon, 2016-2019
Authors: Jennifer C Rowe; Adam Duarte; Christopher A Pearl; Brome McCreary; P K Haggerty; Michael J Adams
Date: 2021-06-04 | Outlet: Ecosphere, v. 12, no. 6, p. e03634
Altered flow regimes can contribute to dissociation between life history strategies and environmental conditions, leading to reduced persistence reported for many wildlife populations inhabiting regulated rivers. The Oregon spotted frog Rana pretiosa is a threatened species occurring in floodplains, ponds, and wetlands in the Pacific Northwest with a core range in Oregon, USA. All life stages of R. pretiosa are reliant on aquatic habitats, and inundation patterns across the phenological timeline can have implications for population success. We conducted capture–mark–recapture (CMR) sampling of adult and subadult R. pretiosa at three sites along the Deschutes River downstream from two dams that regulate flows. We related the seasonal extent of inundated habitat at each site to monthly survival probabilities using a robust design CMR model. We also developed matrix projection models to simulate population dynamics into the future under current river flows. Monthly survival was strongly associated with the extent and variability of inundated habitat, suggesting some within-season fluctuations at higher water levels could be beneficial. Seasonal survival was lowest in the winter for all three sites, owing to limited water availability and the greater number of months within this season relative to other seasons. Population growth for the two river-connected sites was most strongly linked to adult survival, whereas population growth at the river-disconnected site was most strongly tied to survival in juvenile stages. This research identifies population effects of seasonally limited water and highlights conservation potential of enhancing survival of particularly influential life stages.
Papers & Reports Late-season movement and habitat use by Oregon spotted frog (Rana pretiosa) in a large reservoir in Oregon, USA
Authors: Christopher A Pearl; Jennifer C Rowe; Brome McCreary; Michael J Adams
Date: 2022-03-04 | Outlet: Journal of Herpetology
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.
Papers & Reports An updated assessment of status and trend for Cascades Frog in Oregon
Authors: Adam Duarte; Christopher A Pearl; Brome McCreary; Jennifer C Rowe; Michael J Adams
Date: 2021-08-31 | Outlet: Herpetological Conservation and Biology
Conservation efforts need reliable information concerning the status of a species and their trends to help identify which species are in most need of assistance. We completed a comparative evaluation of the occurrence of breeding for Cascades Frog (Rana cascadae), an amphibian that is being considered for federal protection under the U.S. Endangered Species Act. Specifically, in 2018–2019 we resurveyed 67 sites that were surveyed approximately 15 y prior and fit occupancy models to quantify the distribution of R. cascadae breeding in the Cascade Range, Oregon, USA. Furthermore, we conducted a simulation exercise to assess the power of sampling designs to detect declines in R. cascadae breeding at these sites. Our analysis of field data combined with our simulation results suggests that if there was a decline in the proportion of sites used for R. cascadae breeding in Oregon, it was likely a < 20% decline across our study period. Our results confirm that while R. cascadae detection probabilities are high, methods that allow the sampling process to be explicitly modeled are necessary to reliably track the status of the species. This study demonstrates the usefulness of investing in baseline information and data quality standards to increase capacity to make similar comparisons for other species in a timeframe that meet the needs of land managers and policy makers.
Papers & Reports Demography of the Oregon spotted frog along a hydrologically modified river
Authors: Jennifer C Rowe; Adam Duarte; Christopher A Pearl; Brome McCreary; P K Haggerty; John W Jones; Michael J Adams
Date: 2021-06-21 | Outlet: Ecosphere
Altered flow regimes can contribute to dissociation between life history strategies and environmental conditions, leading to reduced persistence reported for many wildlife populations inhabiting regulated rivers. The Oregon spotted frog (Rana pretiosa) is a threatened species occurring in floodplains, ponds, and wetlands in the Pacific Northwest with a core range in Oregon, USA. All life stages of R. pretiosa are reliant on aquatic habitats, and inundation patterns across the phenological timeline can have implications for population success. We conducted capture-mark-recapture (CMR) sampling of adult and subadult R. pretiosa at three sites along the Deschutes River downstream from two dams that regulate flows. We related the seasonal extent of inundated habitat at each site to monthly survival probabilities using a robust design CMR model. We also developed matrix projection models to simulate population dynamics into the future under current river flows. Monthly survival was strongly associated with the extent and variability of inundated habitat, suggesting some within-season fluctuations at higher water levels could be beneficial. Seasonal survival was lowest in the winter for all three sites, owing to limited water availability and the greater number of months within this season relative to other seasons. Population growth for the two river-connected sites was most strongly linked to adult survival, whereas population growth at the river-disconnected site was most strongly tied to survival in juvenile stages. This research identifies population effects of seasonally limited water and highlights conservation potential of enhancing survival of particularly influential life stages.
Papers & Reports Oregon spotted frog (Rana pretiosa) migration from an aquatic overwintering site: Timing, duration, and potential environmental cues
Authors: Jay Bowerman; Christopher A Pearl
Date: 2020-07-16 | Outlet: The American Midland Naturalist 184:87-97
Relatively few North American anurans overwinter in water and information is sparse on their movement from overwintering habitat to breeding sites. Oregon spotted frogs (Rana pretiosa) breed explosively in early spring and often overwinter submerged at sites that are distanced from breeding habitats. In montane parts of their range, wintering and breeding habitats can remain frozen for months. We investigated timing, duration, and potential cues for R. pretiosa migrations from a wintering lake near the Cascade Mountains in central Oregon, U.S.A. First and median migrant males moved slightly earlier than females. Onset of migration was as early as February 12 (males) and as late as April 4 (females) in years of mild and extended winters, respectively. Frogs were active at water temperatures below those associated with early breeding activities in one lowland R. pretiosa population. Higher proportions of frogs migrated before ice-out in years of prolonged winter conditions. Migrations were temporally compressed in years of later movement. This migration ‘rush’, along with the ability to move at cold temperatures and to vary timing of migrations likely helps montane R. pretiosa deal with colder and more variable spring conditions than lowland populations.
Papers & Reports Estimation of metademographic rates and landscape connectivity for a conservation-reliant anuran
Authors: Adam Duarte; James T Peterson; Christopher A Pearl; Jennifer C Rowe; Brome McCreary; Stephanie K Galvan; Michael J Adams
Outlet: Landscape Ecology
Context Amphibian conservation efforts commonly assume populations are tied to waterbodies that collectively function as a metapopulation. This assumption is rarely evaluated, and there is a need to understand the degree of connectivity among patches to appropriately define, manage, and conserve biological populations.
Objectives Our objectives were to quantify local persistence, colonization, and recruitment (metademographic rates) in relation to habitat attributes, evaluate the influence of the spatial arrangement of patches on landscape-scale population dynamics, and estimate the scale at which metapopulation dynamics are occurring for the Oregon spotted frog (Rana pretiosa).
Methods We collected R. pretiosa detection/non-detection data and habitat information from 93 sites spread throughout the species’ core extant range in Oregon, USA, 2010–2018. We developed a spatial multistate dynamic occupancy model to analyze these data.
Results Results indicated the proportion of sites occupied by R. pretiosa was relatively stable despite regular turnover in site occupancy. Connectivity was highest when the distance between sites was within 4.49–https://7.70 km, and populations within 1 km are at the appropriate spatial scale for effective population management. Rana pretiosa metademographic rates were strongly tied to water availability, vegetation characteristics, and beaver dams.
Conclusions Our analysis provides critical information to identify the appropriate spatial scale for effective population management, estimates the distance at which populations are connected, and quantifies the effects of hypothesized threats to species at a landscape scale. We believe this type of model can inform conservation and management strategies for multiple species.
Objectives Our objectives were to quantify local persistence, colonization, and recruitment (metademographic rates) in relation to habitat attributes, evaluate the influence of the spatial arrangement of patches on landscape-scale population dynamics, and estimate the scale at which metapopulation dynamics are occurring for the Oregon spotted frog (Rana pretiosa).
Methods We collected R. pretiosa detection/non-detection data and habitat information from 93 sites spread throughout the species’ core extant range in Oregon, USA, 2010–2018. We developed a spatial multistate dynamic occupancy model to analyze these data.
Results Results indicated the proportion of sites occupied by R. pretiosa was relatively stable despite regular turnover in site occupancy. Connectivity was highest when the distance between sites was within 4.49–https://7.70 km, and populations within 1 km are at the appropriate spatial scale for effective population management. Rana pretiosa metademographic rates were strongly tied to water availability, vegetation characteristics, and beaver dams.
Conclusions Our analysis provides critical information to identify the appropriate spatial scale for effective population management, estimates the distance at which populations are connected, and quantifies the effects of hypothesized threats to species at a landscape scale. We believe this type of model can inform conservation and management strategies for multiple species.
Data Release Oregon spotted frog (Rana pretiosa) monitoring data for metademographic analysis 2010-2018, Oregon: U.S. Geological Survey Data Release
Authors: Jennifer C Rowe; Adam Duarte; James T Peterson; Christopher A Pearl; Brome McCreary; Stephanie K Galvan; Michael J Adams
Date: 2020-05-05 | Outlet: ScienceBase
This dataset contains information from surveys conducted 2010-2018 by USGS as part of a long-term Oregon spotted frog monitoring effort in the central Oregon range. Data consist of site, survey, habitat, and species detection covariates, as well as inter-site distance measurements.
Data Release Annotated bibliography of grazing effects on amphibians and their habitats (ver. 2.0, February 2022)
Authors: Jennifer C Rowe; Christopher A Pearl; Michael J Adams; Brome McCreary
Date: 2022-02-10 | Outlet: Science Base
Livestock grazing is one of the most common land uses in the western United States, where multiple amphibians of conservation concern use habitats that are grazed. Despite the common intersection of grazing and sensitive amphibian species, there are very few reviews of research related to the issue. USGS researchers compiled and summarized literature pertaining to livestock grazing effects on amphibians and their habitats, with an emphasis on wetland-breeding species in the western United States. Users of the annotated bibliography can utilize an integrated search tool with user-defined criteria to query records and output results. This tool aids users in synthesizing research related to a range of specific questions and should assist land managers in evaluating and implementing grazing while maintaining habitat for wetland amphibians.
Data Release Cascades frog (Rana cascadae) historical site surveys in the Oregon Cascade Range, 2018-2019
Authors: Michael J Adams; Christopher A Pearl; Brome McCreary; Jennifer C Rowe
Date: 2019-10-11 | Outlet: Science Base
We used visual surveys to document the presence of all life stages of Cascades frog (Rana cascadae) at historically occupied sites. We surveyed 67 sites 1-2 times between May and August of 2018 and 2019. This effort was a continuation of 2001-2004 surveys conducted at the same site pool. This dataset includes counts of amphibians, reptiles, and fish observed during each site survey, as well as habitat covariates.
Data Release Foothill yellow-legged frog (Rana boylii) surveys in Oregon 2019
Authors: Michael J Adams; Christopher A Pearl; Jennifer C Rowe; Brome McCreary; Matthew B Laramie; David S Pilliod
Date: 2019-11-01 | Outlet: Science Base
We used visual surveys and environmental DNA (eDNA) sampling to document the presence of all life stages of foothill yellow-legged frogs (Rana boylii) at historically occupied sites. We visited 52 stream reaches (sites) on federal and private lands between June and September of 2019. This dataset includes counts of amphibians, crayfish, and fish observed during each site survey, as well as habitat and water sampling covariates.