Cooperative Fish and Wildlife Research Units Program:
Education, Research and Technical Assistance for Managing Our Natural Resources

The eastern indigo snake (EIS; Drymarchon couperi) was federally listed as threatened in 1978, with population declines largely caused by anthropogenically-induced habitat loss. The species has declined throughout its range such that natural populations no longer occur in Alabama, Mississippi, or the Florida panhandle. While EIS persist throughout much of southeastern Georgia and peninsular Florida, ongoing habitat fragmentation, particularly from road mortality, may threaten the long-term viability of remaining populations. As such, empirical modeling approaches are needed to make spatially explicit predictions about the viability of EIS populations.

This project represents a collaboration across multiple state, federal, and non-profit partners to develop spatially explicit population viability models for EIS that incorporate landscape effects on habitat suitability, connectivity, and survival as well as demographic processes such as fecundity and individual growth. The Arizona Cooperative Fish and Wildlife Research Unit is contributing to several components of this project. First, we developed a range-wide connectivity model that explicitly incorporates landscape effects on EIS connectivity. Second, we are developing a survival model to predict EIS survival as a function of road density, sex, and body size. Third, we are assisting in the development of an individual growth model which will allow us to estimate changes in EIS body size over time and thereby predict survival as a function of body size throughout the life of an individual snake. We will continue to collaborate on the development and application of the final population viability model.