There's No Place Like Home: Influential Habitat Characteristics of Eastern Tiger Salamander (Ambystoma tigrinum tigrinum) Breeding Ponds in Maryland and Delaware

Abstract

Habitat loss, degradation, and modification are important drivers of global population declines in amphibians. Most amphibians have a biphasic lifestyle and are susceptible to threats in both aquatic and terrestrial habitats. Eastern Tiger Salamanders (Ambystoma tigrinum tigrinum) are endangered throughout much of their range in the eastern United States, including Maryland and Delaware. Ambystoma t. tigrinum breed in ephemeral freshwater ponds and then migrate into the surrounding terrestrial environment after metamorphosis. Limited research exists about what habitat characteristics play a role in breeding pond use. We sought to understand what features of the breeding pond and surrounding landscape influence abundance and occupancy. We measured salamander occupancy, salamander abundance, and water quality parameters at ponds during the 2018 and 2019 breeding seasons. We used geographic information systems to determine pond area and the percentage of forest area and road density surrounding a pond at four spatial scales. Pond occupancy by A. t. tigrinum was positively associated with increased depth and less forest cover at the largest spatial scales. Abundance of A. t. tigrinum was greatest in larger, deeper ponds, potentially because these factors increase hydroperiod. More basic pH and decreased conductivity were also associated with higher male salamander abundances in ponds. Forest area and road density were not in the top-ranked model, although we note that ponds in this study had a minimum of 70% forest area within 150 m. Our findings elucidate relationships between A. t. tigrinum and their habitat, providing knowledge for future management of this state-endangered species.