Aspects of gopher tortoise (Gopherus polyphemus) populations in Georgia
Ballou, Ashley Rose
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I estimated gopher tortoise population sizes using line transect distance sampling on 17 sites in Georgia, and studied whether burrow width affects detection probability. I used tortoise density data to determine which site and landscape variables affect tortoise population density. I also studied a juvenile tortoise population in southwestern Georgia to test the accuracy of juvenile gopher tortoise burrow scopes, compare juvenile and adult tortoise burrow occupancy and evaluate a new method for tracking juvenile tortoises. Population size estimates among sites ranged from 89 (95% CI: 61-129) to 1877 (95% CI: 1485-2372). I found that detection probability decreased with decreasing burrow width, from 0.78 for burrows > 23 cm to 0.67 for burrows < 12 cm in width. The best model to predict tortoise densities was the model that included evergreen and mixed forest within sites and road density in the surrounding landscape. The juvenile burrow scope was highly accurate (occupancy of 96.7% of burrows was determined correctly), and juveniles had a significantly higher burrow occupancy rate (77%) than adults (40%). Finally, I found that fluorescent powder tracking was a simple and inexpensive method for tracking juvenile gopher tortoises.