Demography and habitat use of boreal toads (Anaxyrus boreas) and other amphibians in northern Wyoming (Blackrock).

Abstract

Amphibian decline is a problem of global importance, with over 40% of species considered at risk. This phenomenon is not limited to the tropics or to other countries. Amphibian species in the U.S. are also declining, contributing to the larger, global phenomenon. For example, in the State of Wyoming, the Wyoming toad has been extirpated in the wild and the boreal toad is a species of special concern. Understanding biotic and abiotic factors that influence amphibian persistence is critical for amphibian conservation. This work in northern Wyoming has focused on demography, habitat alteration and creation, and disease in the context of multiple amphibian populations. One of the foci has been to identify the capacity for mitigation wetlands (those created to offset losses due to, for example, road construction) to serve as habitat for amphibians. Four species of amphibians native to Wyoming, including the boreal toad, reside in this region. Our previous research indicates that the toad population at Blackrock is declining at 5-6% per year and that disease due to the amphibian chytrid fungus is contributing to this decline. Our demographic work at this site began in 2003, focusing solely on the boreal toad. Additional funding in 2012 allowed us to increase the scope of the project and assess chorus frog, salamander and Columbia spotted frog populations, invertebrate assemblages, work to quantify the use of mitigation sites by amphibians, and to expand efforts to include sites on Togwotee Pass a short distance away from Blackrock. Because most previous studies of amphibian use of created wetlands have taken place in the eastern United States, this project, incorporating demographic and disease dynamics as well as community composition and mitigation effects of created wetlands, is unique and provides a case study in the Intermountain West. By 2015, all four native amphibian species were observed at one of the created wetlands, and all of them, including the boreal toad, were breeding (evidenced by breeding behavior, eggs or tadpoles).