Benefits and biases of VHF and GPS telemetry: A case study of American alligator spatial ecology

Abstract

ABSTRACTAmerican alligators (Alligator mississippiensis) historically occupied freshwater habitats such as isolated wetlands, lakes, rivers, bottomland swamps, and floodplains in coastal and inland sites. As a result of loss of aquatic habitats, alligators have adapted to inhabiting human‐made lagoons on golf courses and aquatic habitats in close proximity to developed areas. We conducted a telemetry study of adult (>1.8‐m) male alligators between July 2012 and September 2014 on Jekyll Island, Georgia, USA. Our objective was to compare the efficacy of using very‐high‐frequency (VHF) and Global Positioning System (GPS) telemetry in the framework of understanding the spatial ecology of American alligators in a developed landscape. We present both benefits and biases of using these technologies in studies with large, semiaquatic vertebrates. Global Positioning System telemetry produced larger 100% minimum convex polygon home range sizes (range = 67.0–1,094.0 ha) when compared with VHF telemetry (range = 27.5–596.0 ha). Data collected using a prototype GPS technology custom developed by Advanced Telemetry Systems (ATS, Isanti, MN, USA) allowed for the construction of larger, more biologically accurate home ranges. However, VHF telemetry allowed alligators to be detected in underground habitats where they could not be detected with GPS telemetry and yielded more information on behavior and microhabitat through direct observation. We recommend the use of traditional VHF telemetry to allow researchers to directly observe animal behaviors such as reproduction and foraging in conjunction with GPS telemetry to capture previously unavailable locational data. These data highlight the importance of choosing the appropriate telemetry technology based on habitat type, species, and research objectives. © 2016 The Wildlife Society.