Microhabitat use and migration distance of an endangered grassland amphibian

Abstract

There have been many studies of microhabitat use in forest-dwelling amphibians, but very few for grassland specialists. This study examines habitat use of the endangered California tiger salamander (Ambystoma californiense), which inhabits grasslands in California’s Great Central Valley. We used an extensive drift fence array to capture most of the surface-active salamanders over 2years at two adjacent breeding ponds in a natural prairie ecosystem. Model selection using simultaneous autoregressive models was used to generate models describing the microhabitat use of each of three salamander age classes (adults, juveniles, and metamorphs). Adults tended to use microhabitats with flood intolerant vegetation and juveniles were most often found at higher elevation sites; both of these surprising results suggest that California tiger salamanders favor the driest microhabitats in the prairie. For certain comparisons, significant interaction terms indicated that there is both temporal and spatial heterogeneity in the distribution of A. californiense with respect to proximity to breeding ponds. A literature review indicated that A. californiense have the second longest migration distance reported for any salamander (median=556m) and the longest among ambystomatids. Our results emphasize the importance of replicating landscape ecological studies over sites and years, particularly for endangered taxa where effective management hinges on understanding the variability in habitat use across time and space. They also suggest that habitat use of grassland amphibians may be fundamentally different from that of forest-dwelling amphibians in that they require larger terrestrial buffers and use different microhabitats within those buffers.