A Combination of Environmental and Landscape Variables Drive Movement and Habitat use in Two Anaxyrus sp. in the Eastern Coastal Plain

Abstract

Amphibians are one of the most endangered taxa and are largely threatened by habitat loss. Little work has been conducted on the movement and habitat use of amphibians outside of the breeding season. In this study, we examined the movement patterns of two species of toads inhabiting the Eastern Coastal Plain of Virginia: the Eastern American Toad (Anaxyrus americanus americanus) and the Fowlers Toad (Anaxyrus fowleri). Based on three years of movement data, we estimated the median migration distance of toads from their breeding location and the propensity for site fidelity, related variation in distance traveled to environmental (e.g., rain, temperature, humidity) and landscape variables (e.g., coniferous forests, distance to trails, terrain ruggedness index), and compared microhabitat selection for daytime refugia between the two species. We found the median distance from breeding grounds to be similar between the two species, 63 m for the Eastern American Toad and 64 m for the Fowlers Toad, but Eastern American Toads had a greater range of moved distances (3rd quartiles were 122 m for Eastern American and 73 m for Fowlers Toads). We also found that both species exhibit site fidelity. Distance to trails, proportion of conifer forest, minimum temperature, and 3-day cumulative rainfall related positively with increased movements. Compared to Fowlers Toads, Eastern American Toads favored woody structures and leaf litter for daytime refugia. Our research provides crucial information for two toad species about the extent of their movements and habitat use during the nonbreeding season. To lessen the decline of amphibians, habitat occupied during the nonbreeding season needs to be included in conservation strategies at biologically relevant distances.