14 Oct 2020

Estimating the Density of Secretive, At-risk Snake Species on DoD Installations Using an Innovative Approach: IDEASS

Abstract: The Department of Defense (DoD) expends considerable resources managing and conserving threatened, endangered, or at-risk snake species. Management for these species is often hampered by a lack of basic knowledge regarding their population size and trajectory. The low detectability of most snakes makes it difficult to determine their presence, or to employ traditional methods to estimate abundance. This work demonstrated a novel, simulation-based method, Innovative Density Estimation Approach for Secretive Snakes (IDEASS), for estimating snake density based on systematic road surveys, behavioral observations of snake movement, and spatial movement (radio telemetry) data. This method was used to generate meaningful density estimates for two rare and cryptic snakes of conservation concern, the Southern Hognose and Eastern Diamondback Rattlesnake, at Fort Stewart, Georgia. IDEASS was also applied to an existing dataset to retroactively estimate density of a more common species of management concern, the Western Ratsnake, at Fort Hood, Texas. In all three cases, traditional density estimation via visual surveys and capture-mark-recapture (CMR) failed completely due to lack of captures and re-captures, despite extensive field effort. We conclude that IDEASS represents a powerful tool, and in some cases the only viable method, for estimating density of secretive snakes.