Problematic generalizations: variation across time, space, and taxa shows amphibian landscape ecology requires a closer look

Background/Question/Methods: A necessary prerequisite for effective species conservation is a thorough understanding of the focal species’ habitat preferences.  There have been many studies of the habitat preferences of forest-dwelling amphibians, but very few for grassland specialists, and of those, none have looked at multiple habitat parameters simultaneously.  In this study, we examined the habitat preferences of the endangered California tiger salamander (Ambystoma californiense), which inhabits grasslands in California’s Great Central Valley.  We used drift fences arranged throughout the prairie habitat at prescribed distances from the breeding ponds to capture the majority of surface-active salamanders over the course of two years at two adjacent breeding ponds.  Stepwise selection was used to create a model describing the habitat preferences of each of three different age classes (adults, juveniles, and metamorphs).

Results/Conclusions: Adults preferred habitat with flood intolerant vegetation and juveniles preferred higher elevations.  These preferences were surprising given that they represent the driest portions of the prairie, and amphibians usually select a moist microhabitat.  There were also significant distance*year and distance*pond interactions, indicating that there is both temporal and spatial heterogeneity in the distribution of A. californiense with respect to proximity to breeding ponds.  No previous study has evaluated these interactions simultaneously, and our results emphasize the importance of conducting amphibian landscape ecology studies over multiple sites and years.  Finally, A. californiense was shown to have the second longest migration distance reported for any salamander (median = 556 m) and the longest in its family (Ambystomatidae).  This knowledge of A. californiense’s habitat preferences will allow not only conservation of appropriately sized buffers around its breeding ponds, but will also place an emphasis on identifying and protecting the critical habitat within these buffers.