Insights into habitat utilisation of the hawksbill turtle, Eretmochelys imbricata (Linnaeus, 1766), using acoustic telemetry

Abstract

Patterns of distribution, key biometric parameters and home range extent were determined for hawksbill turtles at Lighthouse Reef Atoll (LRA), Belize over two field seasons (16days, 2009; 30days, 2010). Relative abundance was determined using 49 sightings transects (≈1km) distributed across the atoll and of all turtles encountered (n=68), 91% were immature (CCLmin≤65cm). Habitat type was significantly correlated with abundance, with more turtles encountered on the coral reef than in the lagoon (GzLMM, χ22=6.85, p<0.05; CPUE reef=1.41turtlesh−1, CPUE lagoon=0.62turtlesh−1). Hawksbills were also significantly more abundant within protected areas (GzLMM, χ21=8.69, p<0.05; CPUE Blue Hole Natural Monument (BHNM)=2.96turtlesperson−1h−1; CPUE Half Moon Caye Natural Monument (HMCNM)=2.34turtlesh−1; outside boundaries=0.88 turtlesh−1). Of 26 captures, 19 focal individuals were equipped with ultrasonic transmitters for active acoustic telemetry, and tracked for 6–25days (n=10, 2009; n=9, 2010). Spatial habitat utilisation was found to be highly variable, with large areas of overlap between distinct home ranges. Home range averaged 31.2ha±32.6 (range 5.1–111.3ha) for the juveniles that were successfully tracked (n=15), with maximum displacement in the order of 1.8km±1.0 (range 0.5–4.0km) and net displacement at 1.2km±0.9. This offshore atoll constitutes an important developmental habitat for the regional population and although our tracking durations were limited, home range of juvenile hawksbills at this site is significantly more expansive than that documented elsewhere.