Preliminary observations on movements of tailed frog tadpoles (Ascaphus truei) in streams through harvested and natural forests

The tailed frog (Ascaphus truei) is designated a species "at risk" or "of s pecial concern" in California, Oregon, Washington, and British Columbia. Fo rest practices often have negative impacts on Ascaphus adults and larvae, i ncluding absence from some clearcut areas. Recolonization of logged sites m ay be critical to sustaining productive amphibian populations. Given the un commonly long larval stage of Ascaphus, movements by larvae may be particul arly important in the recolonization of managed forests. We investigated mo vement rates of Ascaphus larvae and the influence of stream parameters in f our stream basins transecting recently harvested and unmanaged forests in s outhwestern British Columbia (1995, 1996, and 1999). Larvae in streams flow ing through unmanaged forests moved about 7.4 times as far as those flowing through clearcuts. Streams with high levels of logjams showed low larval m ovement rates. Recently harvested sites may produce unfavorable conditions impeding recolonization by Ascaphus larvae. High gradient streams also show ed low larval movement rates. The role of stream-dwelling larvae in dispers al of Ascaphus is unknown but would be energy-efficient, because it can be passive with the stream current.