Movement and Survival to Winter Dormancy of Fall-Released Hatchling and Head-Started Yearling Gopher Tortoises

Abstract

Gopher Tortoise (Gopherus polyphemus) populations are declining throughout the southeastern United States. Range-wide conservation efforts include identifying populations that do not currently meet viability criteria but are suitable candidates for population enhancement. We investigated the potential role of head starting as a recovery tool by releasing hatchling and head-started yearling Gopher Tortoises as pairs (n = 28) into adult burrows in fall and comparing their movements and survival until winter dormancy. Head-started yearlings experienced higher predicted survival than did hatchlings (87.7% vs. 56.5%). Head-started individuals also tended to move greater distances between burrows and established dormancy burrows further from their release burrows, but the differences were not significant. Most individuals of both groups used a small number of closely spaced burrows, although hatchlings took longer than head-started individuals to establish their first burrow (11.3 vs. 4.4 d on average) and a higher proportion were depredated or censored before establishing a burrow (35.7% vs. 10.7%). The paired release design provides strong experimental evidence that head-started yearling Gopher Tortoises experience at least a short-term survival advantage over hatchlings, while exhibiting comparable fidelity to the release site. Soft-release pens were not necessary to promote high site fidelity in our study, but the decision as to whether or not to use them at other release sites may be dictated by the predator community and what is practical to implement. We contend that head starting shows promise as a recovery tool for Gopher Tortoises and that hard releases may be a worthwhile option for managers to consider.