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MP2 Amphibian Research and Monitoring
(101) USGS-ARMI amphibian surveys in Yellowstone National Park: Methods, results, and applications.
Patla, D.1, Peterson, C.1, 1 Idaho State University, Pocatello, ID, 83209-8007
ABSTRACT- Assessing amphibian population trends in Yellowstone National Park is challenging due to the large size and extensive wilderness area of the park. Since 2000, with support from USGS-ARMI, we have refined our survey design and techniques, with the objective of determining amphibian site occupancy, distribution, and habitat relationships. To distribute sampling effort we stratify the park's area into blocks, and randomly select catchment basins. Within the selected basins we conduct visual encounter surveys at all potential breeding sites, to the extent feasible. Survey sites are pre-identified with National Wetland Inventory maps and, in 2003, wetland probability maps. In 2002 and 2003, we incorporated repeat-surveys of a proportion of the sites to assess detectability. Surveys were conducted in approximately 19 catchment basins in Yellowstone between 2000 and the end of 2003, with one basin surveyed for 3 of the 4 years. By the end of 2002, we conducted surveys at 370 potentially suitable amphibian breeding sites, finding at least one amphibian in 256 (69%) of these sites. Breeding populations of boreal chorus frogs were found at approximately 126 sites, Columbia spotted frogs at 71, tiger salamanders at 41, and boreal toads at only 9. Breeding sites were predominantly permanent or ephemeral ponds or pools in larger wetlands, with shallow water, emergent sedges, and no fish. Survey results, adjusted for detectability, will provide a basis for monitoring changes in site occupancy and distribution over time, allowing us to discern population declines and trends in habitat use if they occur. Results are also being used to develop habitat probability maps, which should significantly improve the ability to predict amphibian presence in Yellowstone. Continuing data analyses and surveys will allow us test hypotheses about the effect on amphibian populations of factors such as climate change, vegetation trends, introduced species, fire, and park management activities.
Key words: surveys, amphibians, monitoring, Yellowstone National Park
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