Head-starting as a conservation tool for gopher tortoises (Gopherus polyphemus)
Quinn, Daniel Patrick
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Gopher tortoise (Gopherus polyphemus) populations are declining throughout their range and conservation action increasingly requires active management manipulations to mitigate losses. This thesis aimed to evaluate head-starting as a population augmentation tool for a depleted population of gopher tortoises at the Yuchi Wildlife Management Area in Burke County, GA. Specifically, we focused on diet and health in captivity and movement and survivorship after release. Different captive diet supplements fed during head-starting showed little differences in growth and plasma chemistry metrics. Plasma chemistry values were also similar to other head-start and wild gopher tortoise populations. After a soft-release, we radio-tracked two cohorts of head-starts (N = 41) 1-3 times per week for up to 486 days. For our first cohort of head-starts, we documented survivorship rates of 72.7% to first dormancy, 60.6% annually, and 48.4% to second dormancy. Our second cohort had an estimated survivorship of 70.0% to first dormancy at our northern release area. Due to issues with fire ants, we were unable to follow our soft-release methods for our second cohort at our southern release area and only 7.1% of head-starts survived to first dormancy. No head-start moved further than 122.0 m from their release site. We also compared radio-telemetered hatchling (n=10) and head-start (n=10) movement and survivorship after hard release at adult burrows for 62 days. Hatchling and head-starts did not demonstrate significantly different movement patterns. 88.9% of hard-released head-starts survived to dormancy compared to 50.0% of hatchlings; however, this was not significantly different (P = 0.11). Our results suggest that head-start tortoises can be reared on simple diets of leafy greens with a commercial supplement and that head-starting could be a beneficial conservation tool for future augmentation efforts given that threats are mitigated prior to release.