Habitat associations of the Coastal Giant Salamander (Dicamptodon Tenebrosus) at its northern range limit

Abstract

Knowledge of species-environment associations is critical for the management of threatened amphibian populations facing habitat fragmentation and a restricted range. The Coastal Giant Salamander (Dicamptodon tenebrosus) is subject to habitat degradation from logging and human development and is classified as Threatened at its northern range limit in British Columbia, Canada. We examined habitat associations for D. tenebrosus in relation to relative abundance and presence/absence for 32 streams sampled across the approximately 100 km range of the species in British Columbia. Of 12 environmental variables we measured at 100-m stream reaches and the adjacent riparian zone, D. tenebrosus relative abundance was positively associated with stream elevation, forest age, and the percentage of boulders within streams. A higher stream gradient was the best predictor of D. tenebrosus presence within a stream reach, with present sites having a 91% higher gradient than absent sites. When excluding sites with low relative abundance, D. tenebrosus presence was also predicted by greater forest age surrounding streams and higher site elevation. Our study highlights that conservation planning for stream-associated amphibians with patchy distributions may be improved by an understanding of species-specific habitat associations at the stream-reach scale