SREL Reprint #3348

Gopher Tortoise hatching success from predator-excluded nests at three sites in Georgia

Daniel P. Quinn, Tracey D. Tuberville, and Kurt A. Buhlmann

University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina 29802, USA

Introduction: Gopher Tortoise (Gopherus polyphemus) populations are declining throughout their native range in the southeastern United States (Auffenberg and Franz 1982). Research into recruitment could lead to a better understanding of the dynamics of populations and perhaps identify strategies that would allow depleted populations to increase recruitment. Manipulating nest survival rates is one potential conservation strategy that can be used to bolster recovering populations, provided that sources of adult mortality have already been or are being mitigated (Tuberville et al. 2009). Egg hatching success, one of the primary factors influencing recruitment in oviparous reptiles, is controlled by both extrinsic (i.e., environmental factors that affect an egg’s ability to hatch after nest construction) and intrinsic variables that influence egg failure prior to nest construction (i.e., infertility, resource provisioning to the egg or other maternal effects, genetic relatedness or incompatibility of parent pair; Bernardo 1996; Simmons 2005). While intrinsic decreases in recruitment are difficult to counteract, extrinsic threats may be more readily manageable. Perhaps the largest extrinsic threat to Gopher Tortoise hatching success are mammalian meso-predators such as Raccoons (Procyon lotor), Gray Foxes (Urocyon cinereoargenteus), Striped Skunks (Mephitis mephitis), and Nine-banded Armadillos (Dasypus novemcinctus) (Douglas and Winegarner 1977; Landers et al. 1980; Wright 1982; Smith et al. 2013). Consequently, many nest protection measures have been used to help conserve tortoises and other chelonians. It is often assumed that hatching success is higher than if predators had not been removed. However, studies from western ranges document relatively low hatching success even of eggs protected from predation (Epperson and Heise 2003; Hurley 1993; Noel et al. 2012). As part of a separate head-starting study involving the collection of eggs for rearing hatchling Gopher Tortoises, we sought to determine hatching success of protected nests comprising our recipient and two donor sites. Our objectives were to: 1) document and contrast hatching success in the absence of predation among our sites, and 2) demonstrate that our method of protecting nests does not significantly decrease hatching success.

SREL Reprint #3348

Quinn, D. P., T. D. Tuberville, and K. A. Buhlmann. 2016. Gopher Tortoise hatching success from predator-excluded nests at three sites in Georgia. Herpetological Review 47(1): 13-16.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).