Survival assessment and movement analysis of gopher tortoises (Gopherus polyphemus) in south Georgia, USA
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Authors
Le, Christopher, Hien
Issue Date
2024-02-02
Type
Thesis
Language
en_US
Keywords
Academic theses , Biology , Ecology , Gopher tortoise , Global Positioning System , Spatial ecology
Alternative Title
Abstract
The keystone and threatened status of the gopher tortoise (Gopherus polyphemus) makes them a species of interest for wildlife management. Two studies were conducted on gopher tortoises in south Georgia, USA. The first study assessed the survivability of 174 passive integrative transponder (PIT) tagged gopher tortoise hatchlings released in 2008 and 2009 at Reed Bingham State Park (RBSP), Cook County, Georgia. It was hypothesized that 10% (17/174) would be recaptured. From March 2020 to July 2021, release sites Gopher Tortoise Management Area and Pioneer Site were surveyed. Zero (N = 0) of the 174 PIT-tagged hatchling tortoises were recaptured. Suggestions for recapture failure were predation, human presence, detection difficulty, dispersal away from release sites, and Upper Respiratory Tract Disease. The second study analyzed movement activity of an adult male gopher tortoise utilizing Global Positioning System (GPS) technology at Moody Air Force Base, a military installation in Lowndes and Lanier Counties, Georgia. Movement was GPS-tracked from September 2020 to January 2021. GPS data contained location, temperature, and satellite-specific acquisition information. A total of 263 (N = 263) Fixed Locations (FL) were acquired. FL were analyzed for home range, core area, distance >300 m, and nocturnal movement (20:00 – 05:00). Home range increased 10-fold with increasing horizontal dilution of precision (HDOP) (range: 3.55 – 15.86 ha, HDOP ≤ 1.5 – 9.9), core area was 0.13 ha, greatest straight-line distance was 345 m, and 41 nocturnal events occurred. GPS unit troubleshooting and gopher tortoises’ fossorial nature attributed to early battery life depletion and FL accuracy and precision analysis. Most FL occurred in the core area; long distance movement outside the core area was exhibited five times, one included nocturnal movement. Suggestions for long distance movement were habitat quality, overwinter burrowing, reproduction, social interaction, and energy expenditure recovery.
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