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The Oregon spotted frog (Rana pretiosa) is a medium-sized anuran native to the northwestern United States. Body coloration ranges from brown or olive to brick red, usually overlaid with dark, ragged spots. Oregon spotted frogs can be distinguished from other native species by their relatively short hind legs, orange or red wash of color on underside of abdomen and legs, and upturned chartreuse eyes. They are associated with freshwater marshes and lakes where they breed in early spring in the warm emergent shallows. The Oregon spotted frog is highly aquatic and reliant on connected seasonal habitats for breeding, summer foraging, and overwintering.

Oregon spotted frog partially submerged
Adult Oregon spotted frog at Dilman Meadows, near Wickiup Reservoir, OR(Credit: Brome McCreary, USGS. Free to use with credit to Brome McCreary; Ask permission before altering photo.)

Oregon spotted frogs once occurred from southwest British Columbia to northeastern California. They appear to be lost from California and Oregon’s Willamette Valley. Hypothesized reasons for their decline include habitat loss and alteration, introduced predators and competitors, and water quality degradation. More than two-thirds of known populations are currently located along the Cascade Range in central Oregon. The Oregon spotted frog was listed as Threatened under the Endangered Species Act in 2014 and is considered Vulnerable on the Red List of Threatened Species by the International Union for Conservation of Nature.

USGS Research – Status and Trends, Threat Assessments

The USGS Forest and Rangeland Ecosystem Science Center (FRESC) is the Pacific Northwest hub for the US Department of Interior’s Amphibian Research and Monitoring Initiative (ARMI). Interdisciplinary teams of scientists conduct research in support of amphibian conservation efforts. Over the past 15 years, biologists in Dr. Michael Adams’s laboratory at FRESC have monitored occupancy patterns, abundance, and population demography to better understand the status of Oregon spotted frog in Oregon. Through a combination of observational, experimental, and modeling techniques, researchers examine relationships between Oregon spotted frog population trends and habitat variables to understand factors contributing to Oregon spotted frog declines.

Researchers have also evaluated interagency efforts to translocate Oregon spotted frogs. Long-term monitoring of relocated populations through mark-recapture efforts allows researchers to estimate probabilities of site colonization or extinction, as well as survival and growth rates for different sexes and life stages. This information can help managers plan for future translocations by understanding the underlying causes for a project’s success or failure.

USGS researchers disseminate their findings on Oregon spotted frog conservation to the public through various modes, including formal Oregon spotted frog status reports, peer-reviewed journal publications, and the popular media.