Ecology of hawksbill turtles (Eretmochelys imbricata) on a western Caribbean foraging ground

We present results of an inwater research program focusing on basic ecology of juvenile hawksbill turtles (Eretmochelys imbricata) in the Cayman Islands. We made 206 captures of 135 hawksbills in Little Cayman (LC) and 103 captures of 97 hawksbills in Grand Cayman (GC). The Cayman Islands aggregation demonstrated a broad size distribution (20.5–62.6 cm straight carapace length), slow growth rate (3.0 ± 0.9 cm yr−1), and multiple recaptures, suggesting long-term residence in some individuals.

Demonstrated home range was small (mean distance from capture to recapture 545 ± 514 m, range 2–2080 m) although an international tag return suggested a long-range developmental migration. Vertical features provided important habitat in LC, and larger turtles were generally captured in deeper waters. Behavior at sighting varied by habitat: resting, swimming, and feeding were observed in coral reef, reef wall, and hardbottom colonized by sponges and gorgonians, and resting was frequently observed in uncolonized hardbottom.

Images obtained from underwater photographers enhanced understanding of hawksbill foraging behavior: turtles fed on  sponges (particularly the leathery barrel sponge, Geodia neptuni), by scraping the reef, and occasionally by consuming thimble jellyfish Linuche unguiculata. Intra- and interspecific interactions were recorded: an apparently commensal feeding relationship was noted with gray Pomacanthus arcuatus, French Pomacanthus paru, and queen angelfish Holacanthus ciliaris and aggressive, possibly territorial, interactions between hawksbills were observed. We also documented causes of injury and mortality in the study area – including legal, illegal and incidental take, vessel collisions, hurricanes, and natural predation.