Effects of predator exclusion on nest and hatchling survival in the gopher tortoise


  • Associate Editor: Carola Haas.


Gopher tortoise (Gopherus polyphemus) populations are declining throughout the Southeast, and high levels of predation on nests and juveniles have been suggested as a potential contributor to this decline. Therefore, we documented gopher tortoise nest success and hatchling survival relative to mammalian predator control. We used 4, large (approx. 40-ha) fenced, predator exclosures to exclude mid-sized mammalian predators: bobcat (Lynx rufus), raccoon (Procyon lotor), Virginia opossum (Didelphis virginianus), fox (Urocyon cinereoargenteus and Vulpes vulpes), coyote (Canis latrans), nine-banded armadillo (Dasypus novemcinctus), and skunk (Mephitis mephitis); 4 unfenced plots served as controls. We monitored nests for survival through hatching and used radio-telemetry to examine hatchling survival. We radio-tracked 40 hatchlings for up to 329 days, but we were only able to track 8 individuals from a single nest at an unfenced plot because of high nest predation. Mean nest survival was greater at exclosures than at unfenced controls (F1, 2 = 45.80, P = 0.0001). Hatchling survival differed (χ2 = 5.839, P = 0.016) between unfenced plots (37.5%) and exclosures (74.4%), suggesting that mammals also were significant predators of hatchlings. The number of juvenile (<13 cm in diameter) and subadult tortoise burrows (13–21.9 cm) increased over a 6-year period in exclosures, providing further support for an effect of excluding mammalian predators on nest and juvenile tortoise survival. © 2012 The Wildlife Society.