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Endangered Species Research

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ESR 40:17-29 (2019)  -  DOI:

Behavior, growth, and survivorship of laboratory-reared juvenile gopher tortoises following hard release

Thomas A. Radzio1,*, Nicholas J. Blase1, James A. Cox2, David K. Delaney3, Michael P. O’Connor1

1Department of Biodiversity, Earth, and Environmental Science, Drexel University, Philadelphia, Pennsylvania 19104, USA
2Tall Timbers Research Station and Land Conservancy, Tallahassee, Florida 32312, USA
3United States Army Construction Engineering Research Laboratory, Champaign, Illinois 61822, USA
*Corresponding author:

ABSTRACT: Captive rearing represents a vital component of many conservation and research programs. However, captive animals can exhibit unnatural behaviors and experience high predation following release, which can limit reintroduction success and the inferential value of studies that use released animals. Soft-release measures (e.g. penning) can acclimate individuals and limit interactions with predators but can also require considerable resources. We reared hatchling gopher tortoises Gopherus polyphemus in the laboratory for physiology experiments and subsequently hard-released them as yearlings to assess the efficacy of this low-cost release method and to explore possible captivity effects on tortoise behavior, growth, and survivorship. Hard-released yearlings exhibited limited dispersal; most constructed burrows soon after release, and, like wild juveniles, exhibited a preference for burrowing under deadwood. Video observations at burrows indicated natural behavior, including overnighting in burrows, extensive basking directly in front of burrows, and limited time away from these important refugia. Basking tortoises responded to simulated predator approach by rapidly entering burrows, with flight initiation distances and hiding times equivalent or similar to those of wild individuals. Survivorship was comparable to that of soft-released juveniles, but growth was slightly lower than expected based on observations of wild tortoises at the site, possibly reflecting performance immediately following release. Our findings indicate that captive-reared juvenile gopher tortoises respond well to hard release and exhibit natural attributes required to thrive in the wild. Moreover, studies of released juveniles can yield valuable insights into the ecology of a life stage that is poorly understood in most chelonians.

KEY WORDS: Gopherus polyphemus · Turtle · Conservation · Headstarting · Antipredatorbehavior · Thermal ecology

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Cite this article as: Radzio TA, Blase NJ, Cox JA, Delaney DK, O’Connor MP (2019) Behavior, growth, and survivorship of laboratory-reared juvenile gopher tortoises following hard release. Endang Species Res 40:17-29.

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