Distribution and habitat of Ascaphus truei in streams on managed, young growth forests in north coastal California

We studied the distribution and habitat of larval Ascaphus truei in first a nd second order streams of managed forests in north coastal California from 1993-1996. Of 72 streams randomly selected to relate landscape variables t o the presence of A. truei, 54 (75%) contained larvae. Geologic formation w as the only landscape variable that predicted the presence of A. truei in a stepwise logistic regression (SLR) model. A second survey was conducted to determine which habitat variables of stream reaches were related to the pr esence of A. truei. Larvae were found in 18 (37%) of 49 stream reaches with flows >1500 cm(3)/sec, and percent fines (negative association with frog p resence), stream gradient (positive association), and water temperature (ne gative association) were the only habitat variables of 21 measured that ent ered a SLR model to predict the presence of A. truei. Only stream gradient differed significantly between reaches with and without tailed frogs; canop y cover, temperature, and forest age were not significantly different. A fi nal survey to further define the microhabitat used by larval A. truei showe d that larvae were found more often than expected in high gradient riffles and less often than expected in pools and runs. Occurrence of larvae was po sitively associated with cobble, boulder, and gravel substrates with lower embeddedness, and negatively associated with fine substrates. We discuss th e comparative habitat requirements and sensitivities to land management act ivities of the two amphibian headwater stream inhabitants, A. truei and Rhy acotriton variegatus, in our study area.