Population consolidation and head-starting as demographic rescue of a low-density gopher tortoise population

Context Gopher tortoises, Gopherus polyphemus, are a keystone species of south-eastern North America due to their historically high density, grazing habits, and the burrows that they maintain across upland landscapes. Many gopher tortoise populations are demographically non-viable due to low population density and/or population size. Management for this species frequently utilize measures such as translocation and head-starting. Aims Between 2020 and 2024, we used short-distance translocation to consolidate a low-density resident population of gopher tortoises and monitored spatial biology and apparent survival in the translocated animals immediately following translocation. We also conducted head-starting of tortoises collected as eggs from the same site and manipulated head-start release conditions to test whether soft- versus hard-release affected apparent survival. Methods We tracked both wild and head-started tortoises via radiotelemetry for 1 year during and 1 year after penning; we determined apparent survival by direct observation of individuals remaining alive and within the site approximately 1.5 years after all enclosure pens had been removed. Key results Home ranges of free-ranging tortoises were approximately the same in the enclosure pen as they were after the enclosure pen was removed, but apparent survival of free-ranging tortoises at the study site was only 56% after the enclosure was removed. Male adult tortoises had higher apparent survival in the site than did females, and translocation distance was a negative predictor of apparent survival. Release condition did not affect head-started tortoise apparent survival, and overall apparent survival of head-started tortoises was 70% 2 years after release. Conclusions Head-starting and direct hard release of juveniles are likely to be successful tools for gopher tortoise conservation, whereas population consolidation may cause poor adult survival and/or site fidelity. Implications Short-distance translocations of wildlife populations should be further studied before this tool is more broadly applied in conservation projects.