Short-term survival and behavior of captive-reared yearling gopher tortoises following hard release
Captive-reared animals often exhibit difficulty adjusting to life when released into the wild. This can impede research or conservation efforts that depend upon raising animals in captivity. Current ideas for conservation of the gopher tortoise, a burrowing turtle of the southeastern United States, include captive breeding and subsequent release of individuals into nature. We collected hatchling gopher tortoises from natural nests and raised them in the laboratory for physiology experiments that required having animals in controlled environments for a prolonged period. Upon completing the lab work, we outfitted 30, one-year old individuals with radio transmitters and hard-released them at their nest sites to determine post-release survivorship and behavior. We report on the survival, activity, and behavior of these tortoises.
Released yearling tortoises exhibited survivorship similar to that of wild yearlings. Most constructed burrows soon after release, and, like wild tortoises, released tortoises disproportionately placed burrows under large pieces of deadwood. Video cameras located at tortoise burrows indicated normal activity patterns. Tortoises slept in burrows at night, emerged during warm daylight hours, basked extensively at burrow entrances, and limited time spent foraging away from the safety of burrow areas. Importantly, simulated predator approaches revealed that basking tortoises exhibited normal antipredator responses by reliably fleeing into their burrows. Despite having been raised inside plastic boxes and having daily contact with laboratory personnel for the first year of their life, captive-reared yearling tortoises retained critical traits necessary for success in the wild. These findings indicate that young gopher tortoises used in lab studies or captive-reared in efforts to augment or propagate wild populations may be successfully hard-released back into nature.