The distribution, relative abundance, and habitat associations of amphibians on the Targhee National Forest

Authors(s): R. J. Clark, C. R. Peterson and P. E. Bartelt

Publication:

Publisher:

Publication Date: 0000-00-00

Type: Final report

Location: Boise ID

Abstract: The objectives of this study were: (1) to determine the distribution of amphibians throughout the Targhee National Forest (TNF); (2) to determine relative abundances of amphibians in the TNF; and (3) to describe the habitat associations of each species located within the TNF. Obrtaining this information is important for several reasons. First, it should aid managers in making land-use decisions that will minimize derimental effects on amphibians, especially sensitive species such as the spotted frog. Second, because amphibians are potentially sensitive indicators of environmental changes, changes in amphibian populations may reveal environmental problems such as water pollution. Third, a better understanding of amphibian distribution and abundance in the TNF may provide clues as to why amphibian populations are declining elsewhere in the world. To accomplish these objecives, we gathered distribution and habitat data from a variety of sources, including the literature, museum records, observations, and a field survey of 98 sites, performed during the spring and summer of 1992. Selection criteria for the sampling sites included recommendations form Forest Service personnel and the presence of historical records. The main sampling technique employed in the field survey was timed searches in which we counted or estimated the number of egg masses, larvae, juveniles, and adults (seen or heard). We also gathered data on the physical and biological conditions at each site (elevation, weather, water temperature, pH, conductivity, wetland type, vegetation, other amphibian species, potential predators, and evidence of grazing). Our general findings were: 1. Amphibians were unevenly distributed throughout Targhee National Forest, with the largest number of amphibian sites in the Island Park and Ashton Districts and the fewest number in the Palisades District. 2. No significant relationships were found between the occurrence of amphibians and elevation, pH, conductivity, or evidence of grazing. 3. Amphibians were most lightly associated with palustrine wetland habitats. 4. The distribution and abundance of amphibians (especially tiger salamanders and chorus frogs) were probably underestimated because of the early spring and low precipitation in 1992. Species specific findings included: 1. Tiger salamander larvae occurred at 9 of 98 survey sites (8%), were locally abundant, occurred only in palustrine habitats, and did not co-occur with western toads. 2. Western toads occurred at 8 of 98 survey sites (8%), were less abundant than our expectation (which was based on historical records), occurred in both palustrine and riverine habitats, and were strongly associated with spotted frogs. 3. Chorus frogs occurred at 8 of 98 survey sites (8%), occurred in all three wetland types, but most often in palustrine habitats. 4. Spotted frogs occurred at 41 of 98 survey sites (42%), were abundant, and were found in all three wetland habitat types. 5. Leopard frogs were not found at any of the survey sites, even though there are historical records for this species on the forest.

Keywords: animal, herpetology, amphibian, frog, Anura, Ranidae, Bufonidae, toad, salamander, Caudata, Targhee National Forest, population, habitat, tiger salamander, Ambystoma tigrinum , western toad, Bufo boreas, chorus frog, Pseudacris triseriata, spotted frog, Rana pretiosa, leopard frog, Rana pipiens