Christopher A Pearl
Science and Products
Herpetological Research Team (FRESC)
The Herpetological Research Team focuses on issues related to conservation and management of amphibians and other aquatic and semi-aquatic species. Among our current studies are effects of invasive species, disease, and land use change on the dynamics of amphibian communities to inform conservation and management decision making.
Oregon Spotted Frog (Rana pretiosa) Monitoring at Jack Creek 2015-2016
This dataset contains information from mark-recapture and egg mass surveys conducted by USGS as part of an ongoing Oregon spotted frog (Rana pretiosa) monitoring effort at Jack Creek, Klamath County, Oregon. Data consist of spotted frog counts aggregated by date, location, life stage, and sex, as well as data on environmental conditions at the time each survey.
Oregon Spotted Frog (Rana pretiosa) Monitoring in the Oregon Cascades 2012-2016
This dataset contains information from visual encounter surveys conducted between 2012 and 2016 by USGS as part of an ongoing Oregon spotted frog (Rana pretiosa) monitoring effort in the Oregon Cascade Mountain Range. We surveyed 91 sites using a rotating frame design in the Klamath and Deschutes Basins, Oregon, which encompass most of the species' core extant range.
Effect of amphibian chytrid fungus (Batrachochytrium dendrobatidis) on apparent survival of frogs and toads in the western USA
Despite increasing interest in determining the population-level effects of emerging infectious diseases on wildlife, estimating effects of disease on survival rates remains difficult. Even for a well-studied disease such as amphibian chytridiomycosis (caused by the fungus Batrachochytrium dendrobatidis [Bd]), there are few estimates of...
Russell, Robin E.; Halstead, Brian J.; Mosher, Brittany; Muths, Erin L.; Adams, Michael J.; Campbell Grant, Evan H.; Fisher, Robert N.; Kleeman, Patrick M.; Backlin, Adam R.; Pearl, Christopher; Honeycutt, R. Ken; Hossack, Blake R. Disentangling effects of invasive species and habitat while accounting for observer error in a long-term amphibian study
The invasive American bullfrog (Lithobates catesbeianus) and a variety of non‐native sport fish commonly co‐occur in lowland lentic habitats of the western United States. Both invasive taxa are implicated in declines of native amphibians in this region, but few long‐term studies of communities exist. Further, field studies of invasive–native...
Rowe, Jennifer; Duarte, Adam; Pearl, Christopher; Mccreary, Brome; Galvan, Stephanie; Peterson, James T.; Adams, Michael J. Quantifying climate sensitivity and climate-driven change in North American amphibian communities
Changing climate will impact species’ ranges only when environmental variability directly impacts the demography of local populations. However, measurement of demographic responses to climate change has largely been limited to single species and locations. Here we show that amphibian communities are responsive to climatic variability, using >...
Miller, David A.W.; Campbell Grant, Evan H.; Muths, Erin L.; Amburgey, Staci M.; Adams, M.J.; Joseph, Maxwell B.; Waddle, J. Hardin; Johnson, Pieter T.J.; Ryan, Maureen E.; Schmidt, Benedikt R.; Calhoun, Daniel L.; Davis, Courtney L.; Fisher, Robert N.; Green, David M.; Hossack, Blake R.; Rittenhouse, Tracy A.G.; Walls, Susan C.; Bailey, Larissa L.; Cruickshank, Sam S.; Fellers, Gary M.; Gorman, Thomas A.; Haas, Carola A.; Hughson, Ward; Pilliod, David S.; Price, Steven J.; Ray, Andrew M.; Sadinski, Walter; Saenz, Daniel; Barichivich, William J.; Brand, Adrianne B.; Brehme, Cheryl S.; Dagit, Rosi; Delaney, Katy S.; Glorioso, Brad M.; Kats, Lee B.; Kleeman, Patrick M.; Pearl, Christopher; Rochester, Carlton J.; Riley, Seth P. D.; Roth, Mark F.; Sigafus, Brent Late-season movement and habitat use by Oregon spotted frogs (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...
Pearl, Christopher; Mccreary, Brome; Rowe, Jennifer; Adams, M.J. Regional variation in drivers of connectivity for two frog species (Rana pretiosa and R. luteiventris) from the U.S. Pacific Northwest
Comparative landscape genetics has uncovered high levels of variability in which landscape factors affect connectivity among species and regions. However, the relative importance of species traits versus environmental variation for predicting landscape patterns of connectivity is unresolved. We provide evidence from a landscape genetics study of...
Robertson, Jeanne M.; Murphy, Melanie A.; Pearl, Christopher; Adams, M.J.; Paez-Vacas, Monica I.; Haig, Susan M.; Pilliod, David S.; Storfer, Andrew; Funk, W. Chris Effect of cattle exclosures on Columbia Spotted Frog abundance
Livestock grazing is an important land use in the western USA and can have positive or negative effects on amphibians. Columbia Spotted Frog (Rana luteiventris) often use ponds that provide water for cattle. We conducted a long-term manipulative study on US Forest Service land in northeastern Oregon to determine the effects of full and partial...
Adams, M.J.; Pearl, Christopher; Chambert, Thierry; Mccreary, Brome; Galvan, Stephanie; Rowe, Jennifer A new parameterization for integrated population models to document amphibian reintroductions
Managers are increasingly implementing reintroduction programs as part of a global effort to alleviate amphibian declines. Given uncertainty in factors affecting populations and a need to make recurring decisions to achieve objectives, adaptive management is a useful component of these efforts. A major impediment to the estimation of demographic...
Duarte, Adam; Pearl, Christopher; Adams, M.J.; Peterson, James Using occupancy models to accommodate uncertainty in the interpretation of aerial photograph data: status of beaver in Central Oregon, USA
Beavers (Castor canadensis) influence habitat for many species and pose challenges in developed landscapes. They are increasingly viewed as a cost-efficient means of riparian habitat restoration and water storage. Still, information on their status is rare, particularly in western North America. We used aerial photography to evaluate changes in...
Pearl, Christopher A.; Adams, M.J.; Haggerty, Patricia K.; Urban, Leslie
Short-term occupancy and abundance dynamics of the Oregon spotted frog (Rana pretiosa) across its core range
The Oregon spotted frog (Rana pretiosa) occupies only a fraction of its original range and is listed as Threatened under the Endangered Species Act. We surveyed 93 sites in a rotating frame design (2010–13) in the Klamath and Deschutes Basins, Oregon, which encompass most of the species’ core extant range. Oregon spotted frogs are...
Adams, M.J.; Pearl, Christopher A.; Mccreary, Brome; Galvan, Stephanie Invasive crayfish as vectors of mercury in freshwater food webs of the Pacific Northwest
Invasive species are important drivers of environmental change in aquatic ecosystems and can alter habitat characteristics, community composition, and ecosystem energetics. Such changes have important implications for many ecosystem processes, including the bioaccumulation and biomagnification of contaminants through food webs. Mercury...
Johnson, Branden L.; Willacker, James J.; Eagles-Smith, Collin A.; Pearl, Christopher A.; Adams, M.J. New Host and Distribution Records of the Leech Placobdella sophieaeOceguera-Figueroa et al., 2010 (Hirudinida: Glossiphoniidae)
Placobdella sophieae Oceguera-Figueroa et al., 2010 (Hirudinida: Glossiphoniidae) is reported from Oregon, California, and British Columbia for the first time. New hosts reported for P. sophieae include Taricha granulosa (rough-skinned newt), Rana pretiosa (Oregon spotted frog), and Anaxyrus boreas (western toad). Placobdella sophieae exhibits...
Moser, William E.; Bowerman, Jay; Hovingh, Peter; Pearl, Christopher A.; Oceguera-Figueroa, Alajandro Roles of patch characteristics, drought frequency, and restoration in long-term trends of a widespread amphibian
Despite the high profile of amphibian declines and the increasing threat of drought and fragmentation to aquatic ecosystems, few studies have examined long-term rates of change for a single species across a large geographic area. We analyzed growth in annual egg-mass counts of the Columbia spotted frog (Rana luteiventris) across the northwestern...
Hossack, Blake R.; Adams, M.J.; Pearl, Christopher A.; Pilliod, David S.; Corn, P. Stephen
Annotated Bibliography: Grazing Effects on Amphibians and Their Habitats
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.
Disentangling Invasive Species and Habitat Effects in a Long-term Amphibian Study
In the Willamette Valley, Oregon, the invasive American bullfrog and a variety of non-native sport fish are implicated in declines of native amphibians. Few long-term community studies of invasive-native interactions exist, and such studies are often complicated by confounding habitat modifications.
Autumn Movements of Oregon Spotted Frog and Winter Habitat Use in the Cascade Mountains of Oregon
The Oregon spotted frog is endemic to the Pacific Northwest where loss and alteration of wetland habitats have contributed to declines in the species. Like many amphibians, the Oregon spotted frog uses multiple habitats across seasons.
Large-scale Review of Amphibian Species and Community Response to Climate Change
Amphibian species and community richness has been declining in North America and climate change may play a role in these declines. Global climate change has led to a range shift of many wildlife species and thus understanding how these changes in species distribution can be used to predict amphibian community responses that may improve conservation efforts.
Drivers of connectivity for two frog species from the U.S. Pacific Northwest
Landscape genetics illustrate how landscape features influence species connectivity and can provide insights for species conservation efforts;however, factors that influence connectivity vary considerably, even among species occupying similar landscapes.