Christopher A Pearl

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 exclosures that limited cattle access to...

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 rates often used to parameterize and...

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 beaver occupancy between 1942–1968 and 2009...

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 declining in abundance and probability of site occupancy...

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 concentrations were measured in 2 nonnative and 1...

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 relatively low host specificity and all...