Switching Bait as a Method to Improve Freshwater Turtle Capture and Recapture Success with Hoop Net Traps

Abstract

We surveyed freshwater turtles at sites in the Lower Rio Grande Valley and Bastrop Lost Pines ecoregions of Texas annually since 2008 and 2009, respectively, and found that captures and recaptures per unit effort (CPUE and RPUE, respectively) decreased annually. In 2011, we tested whether or not switching the type of bait used to attract turtles affected CPUE and RPUE. Under the assumption that bait preferences af- fect capture probabilities both among and within species, we hypothesized that switching bait would increase CPUE in 2011 by attracting individuals not captured in previous years. We also hypothesized that low recapture success in previous years was due to an olfactory-induced trap-shy response. We tested this hypothesis by determining if RPUE increased when we switched the type of bait used to attract turtles. We found that switching from fi sh-based bait to red meat signifi cantly increased CPUE, but not RPUE, for Trachemys scripta elegans (Red-eared Slider). We also found weak evidence that Apalone spinifera emoryi (Texas Spiny Softshell) preferred red meat over fi sh-based bait. The results of this study indicate that switching bait can be an effective way to maximize CPUE across multiple years when monitoring freshwater turtles using baited hoop nets. However, switching bait did not affect RPUE, which indicates that the apparent trap-shy behavior of turtles in our study areas is not driven by an olfactory-induced response to the type of bait used.