Home range and movements of American alligators ( Alligator mississippiensis ) in an estuary habitat

Abstract

Background Understanding movement patterns of free-ranging top predators throughout heterogeneous habitat is important for gaining insight into trophic interactions. We tracked the movements of five adult American alligators to delineate their estuarine habitat use and determine drivers of their activity patterns in a seasonally-fluctuating environment. We also compared VHF- and satellite-tracks of one of the alligators to examine tradeoffs in data quality and quantity. Results All tracked alligators showed high site fidelity in the estuary, but estimated home range size and core-use areas were highly variable. Two alligators were relatively sedentary and remained in the upper stream zone. One alligator traveled to a transition zone between freshwater marsh and estuary habitat, but primarily remained in the upstream area. Two alligators traveled to the downstream zone into saline conditions and showed high salinity tolerance. Overall movement rates were highly influenced by salinity, temperature, and season. Both satellite and VHF radio telemetries resulted in similar home range, core-use area, and activity centers. Conclusions This study reveals consistent use of estuary habitat by American alligators. The alligators showed variations in their movement pattern and seasonal habitat, with movement attributable to environmental factors. Although satellite-derived locations were more dispersed compared to locations collected using VHF radio-tags, data collected from VHF tracking omitted some habitat used for a short period of time, indicating the effectiveness of satellite telemetry to continuously track animals for ecosystem-scale studies.