The status of western toads (Bufo boreas), Northern Leopard Frogs (Rana pipiens), and Common Garter snakes (Thamnophis sirtalis) in Idaho and the Greater Yellowstone Ecosystem

Authors(s): C. R. Peterson

Publication: conference on declining and sensitive amphibians in the Rocky Mountains and Pacific Northwest

Publisher: (unpublished) Idaho Herpetological Society and US Fish and Wildlife Service, Snake River Basin Office, Boise ID

Publication Date: 0000-00-00

Type:

Location: Boise ID

Abstract: The population status of western toads varies in different portions of its range. Western toads appear to be widely distributed and common in much of Idaho, including southwestern, west central, and parts of northern Idaho (eg, Craig Mountain). Relatively few toad populations have been found in the Couer d'Alene basin, Potlatch Timber Corporation operating area, the Bighorn Crags, the Lost River Range, and on the Targhee National Forest. Comparisons of historical records with recent survey data in southeastern Idaho and the GYE indicate a substantial decrease in the number and size of toad populations. Several factors may have contributed to these apparent declines, including drought and habitat modification. Certain water chemistry variables (eg, pH, conductivity, and total ions) are significantly higher for toad breeding sites than for nonbreeding sites in the GYE. Consideration of the distribution and relative abundance data for both Idaho and the GYE suggests that Western Toads are doing less well at higher elevations. The distribution and relative abundance of Northern Leopard Frogs appears to have decreased considerably in southern Idaho and the GYE. This conclusion is based on comparisons of historical records and recent surveys, and on a mail questionnaire survey of Idaho field biologists in 1990. Although a number of factors probably contributed to these apparent declines, drought conditions during the late 1980s and early 1990s may have been particularly important. In 1995 and 1996, we found an increased number of leopard frogs in our amphibian surveys and have received more contributed observations for them than in the previous size years. The first leopard frog observation in over 20 years was reported for Grand Teton National Park in 1996. Although the number of sites where we are detecting leopard frogs has recently increased, this species still appears to be missing from many sites where it occurred in the past. The distribution and relative abundance of Common Garter Snakes apparently has declined in southeastern Idaho and in the GYE. Although Carpenter's 1951 herpetological survey of the Jackson Hole region indicated that this species was common, we have failed to find them in our studies in this area and have received few reports of their occurrence there. We also have found relatively few Common Garter Snakes in southeastern Idaho. Given that amphibians are important prey for Common Garter Snakes, it is possible that apparent snake declines are related to amphibian declines in these areas. Common Garter Snakes still appear to be widely distributed elsewhere in Idaho but the lack of historical information on relative abundance makes it difficult to ascertain if there has been a decrease in relative abundance. To obtain more information on the status of Common Garter Snakes, I recommend that the occurrence and numbers of this species be noted in future herpetological surveys and be reported to the appropriate regional database.

Keywords: animal, herpetology, amphibian, toad, frog, Anura, Ranidae, Bufonidae, Amphibia, reptile, snake, western toad, predation, food, Idaho, population, breeding, mortality, habitat, Bufo boreas, habitat, leopard frog, northern leopard frog, Rana pipiens, common garter snake, garter snake, Thamnophis sirtalis, Reptilia, Squamata, Colubridae, Jackson Hole, Teton County, Targhee National Forest, Greater Yellowstone Ecosystem, Grand Teton National Park