GPS Technology Reveals Larger Home Ranges for Immature Gopher Tortoises

Abstract

Movement data and estimation of home-range sizes provide insight into the types and amount of habitat needed to support wildlife populations, which is critical for conservation planning. Gopher Tortoises, which are important ecosystem engineers and keystone species across the southeastern United States, are experiencing ongoing population declines and warrant additional habitat protection and management throughout their range. Conservation assessments for Gopher Tortoises are currently limited by scant knowledge of the ecology of younger age classes. We implemented a short-term study of immature Gopher Tortoise spatial ecology at Archbold Biological Station (ABS), Florida to determine home-range size, movements, and activity levels of 3-7-yr-old tortoises. We used GPS technology to obtain high-resolution temporal tracking data (approximately 10-fold increase compared with the radio tracking frequency in prior studies). Despite the relatively short duration of our study (≤40 d), immature Gopher Tortoises (n = 6) at ABS had home-range sizes ranging from 0.38 to 1.46 ha, which are approximately 6.6-fold larger than previously reported annual home-range estimates. Tortoises also left their burrows more often (4.0 ± 3.2 SD times per day) and for longer duration (31.5 ± 10.6 SD min per emergence) than in studies conducted elsewhere (1.6 times and 18.8 min, respectively). Our results illustrate the importance of employing new technologies to track previously difficult-to-observe life stages and improve conservation efforts for imperiled species.