The influence of urban development on populations of amphibians has received a significant amount of attention in the recent literature. However, few studies have attempted to obtain demographic data on amphibians in urban landscapes. To assess the influence of urbanization on amphibian life histories, we collected demographic and phenologic data on an urban population of the California tiger salamander (Ambystoma californiense) in Sonoma County, California. This population breeds in a single isolated vernal pool nested in a mosaic of urban land uses. We used drift fences with pitfall traps to capture adults migrating to and from the pool over the course of 3 breeding seasons. We estimated the breeding adults at between 65 and 107 annually, which was somewhat surprising given that only 17.5% of the grassland habitat surrounding the pool is currently undeveloped. The study population had similar temporal patterns of migration activity among years. Rainfall triggered migration to the breeding pool, and males remained at the pool longer than females. Migration activity began in November, but most breeding adults were captured in December and January, and captures in February were rare. The migration pattern associated with pool depth showed a trimodal distribution; however, minimum pool depth for breeding occurred when the pool was approximately half full to completely full. Finally, we were able to stimulate colonization by gophers of areas near the breeding pool by constructing large mounds of soil. Our trapping records indicate that some salamanders over-summered in these areas where no suitable upland burrows existed prior to mound construction. Although developed landscapes are less than optimal for the long-term conservation of this species, our study shows that populations may persist with some degree of adjacent development.
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