Short-term effects of handling and permanently marking gopher tortoises (Gopherus polyphemus) on recapture rates and behavior

Abstract

Limited evidence in the literature suggests that the assumption of equal catchability in mark-recapture studies of turtles may be invalid. These papers suggest that turtles may alter their behavior to avoid recapture following initial handling. If turtles are less likely to be recaptured following initial capture and handling, then population models estimating demographic characteristics and population sizes from mark-recapture data may be invalid (e.g., overestimating population size). Because conservation and management decisions are largely based on population sizes and trends, it is essential to investigate whether marking animals has any effect on behavior. We tested the effects of handling and permanently marking gopher tortoises (Gopherus polyphemus) at the Kennedy Space Center, Florida from 20-22 July 2003 to determine if short-term activity and recapture rates were affected. We used two distinct groups of tortoises: one group was handled (captured, measured, marked) and the other was not handled, but was marked with paint from a distance of 2.2 m. Although the behavior of handled and non-handled animals was distinct, we found no differences in recapture rates or time to recapture between the groups. We suggest that handled gopher tortoises are as likely to be recaptured as tortoises that have not been handled, although more subtle or long-term effects cannot be ruled out.