COS 24-8
Persistence of Columbia spotted frogs in the Great Basin: Quantifying habitat quality, connectivity, and climate suitability

Tuesday, August 12, 2014: 10:30 AM
Regency Blrm A, Hyatt Regency Hotel
Robert S. Arkle, U.S. Geological Survey, Forest & Rangeland Ecosystem Science Center, Boise, ID
David S. Pilliod, U.S. Geological Survey, Forest & Rangeland Ecosystem Science Center, Boise, ID

Columbia spotted frogs in southeastern Oregon, southern Idaho, and Nevada constitute a genetically distinct population segment (DPS) of Rana luteiventris. This Great Basin DPS has been a Candidate for Listing under the Endangered Species Act since 1993 because remaining populations are small, isolated, and reside in habitats altered by water development, livestock use, mining, and non-native species. Projected warmer, drier climate conditions could further stress and isolate already vulnerable populations in the region. We used existing data on spotted frog occurrence, abundance, and habitat to understand factors influencing habitat quality, habitat connectivity, and climate suitability in the Great Basin. 


Preliminary results suggest that the area of the Great Basin with suitable climates for spotted frogs has already decreased over the past 100 years and will continue to decrease substantially over the next 100 years. Analysis using circuit and random walk theories suggests that connectivity between adjacent occupied sites is currently low, while sub-populations are isolated from one another, a finding supported by genetic analyses. Preliminary results for all three states concur that spotted frogs are strongly associated with relatively deep (>1 m) water bodies that contain abundant emergent vegetation and non-trout fish species. Streams with beaver were 2.5 times more likely to be occupied than ponds, lakes, or streams without beaver. Over 75% of occupied sites had no or low cattle grazing impacts to habitat structure or water quality, a finding possibly related to emergent vegetation height and abundance. The presence of trout species reduced occupancy probability by half compared to sites with only non-trout fish. We conclude that careful beaver reintroduction, grazing management, and non-native trout control efforts may provide valuable tools for the conservation of the Columbia spotted frog in the Great Basin.