Multi-Scale Habitat Selection in an Isolated Population of Wood Frogs (Lithobates sylvaticus) and its Interaction with Chytrid Fungus

Isolated populations that are separated from a species' more contiguous range may be particularly susceptible to stressors such as habitat degradation or disease. Amphibians have experienced population declines worldwide due to habitat change and the chytrid fungus (Batrachochytrium dendrobatidis [Bd]). Understanding habitat requirements for isolated populations of conservation concern is essential for effective management and species persistence. Moreover, the extent to which amphibians can modulate negative effects of disease via microhabitat choice remains unknown. Wood Frogs (Lithobates sylvaticus) in Wyoming, United States exist as isolated, glacial relict populations. We examined habitat selection in Wood Frogs across multiple seasons and spatial scales and in relation to Bd infection status. We tracked 170 Wood Frogs at five sites in the Snowy Range of Wyoming during May–October of 2020 and 2021. We swabbed each Wood Frog for Bd and quantified macrohabitat, microhabitat, and microsite attributes. During summer and fall, Wood Frogs tended to remain close to waterbodies and within aspen, willow, and wet meadow macrohabitats. Wood Frogs also preferred aquatic macrohabitats during summer and forest macrohabitats during fall. Summer microhabitat selection included dense and tall vegetation, high soil moisture, and close proximity to standing water and cover. Sixty-two percent of Wood Frogs tested positive for Bd at least once. When Bd-positive, Wood Frogs in terrestrial habitats switched to areas with higher soil moisture. Our results demonstrate spatiotemporal variation in habitat preferences of an isolated amphibian population of concern and contribute to a growing body of evidence demonstrating relationships between animal behavior, habitat, and disease.