Oregon Spotted Frog

Name: Heidy Peterson
Email: hkpeterson@hotmail.com

Position: M.Sc. 2001

Project: Competition and Predation Factors Influencing Larval Survival of the Oregon Spotted Frog (Rana pretiosa) in Southwestern British Columbia.

Oregon spotted frogs range from Northern Oregon to southern British Columbia west of the Cascade Range. Their close relative, the Columbia spotted frog, (Rana luteiventris) has a range extending to Montana, as far south as Utah, and into northern British Columbia, and is not especially rare. Even though the two species have similar life histories and habitat use patterns, the Oregon spotted frog appears to persist in only a limited number of populations, two of which are in Southwestern British Columbia. Egg deposition occurs in early spring in shallow breeding pools where eggs risk becoming stranded and desiccating. Throughout their life, spotted frogs never venture far from the water and for this reason may be more susceptible to predators such as bullfrogs and introduced fish. Little is known about the species, especially in British Columbia where the latest published work dates back to the mid-1970s. Due to the pressing needs for conserving the small population, management and recovery efforts for the Oregon spotted frog are underway in British Columbia.

The species was red-listed in November 1999 through an emergency COSEWIC process. Current estimates of breeding adults are at less than 300 for British Columbia. A Recovery Team will begin to address some of the issues surrounding the decline of the Oregon spotted frog by conducting inventory activities at candidate sites, mark-recapture efforts, and developing effective captive rearing techniques for possible reintroduction.

My research will focus on the factors influencing the early life history of the Oregon spotted frog, in southwestern British Columbia. The species is extremely rare in the Pacific Northwest and various explanations have been offered for its precarious population status, including bullfrog predation, habitat loss, spread of exotic plants, and changes in wetland hydrology due to development. I will experimentally evaluate the survival of spotted frog tadpoles to determine if competition from other anurans, predation by common wetland animals, or behavioral characteristics are possible causes of mortality prior to metamorphosis. Through my research I hope to gain insight into factors that are influencing larval survival that may be addressed through a long-term conservation plan.