Dive behaviour of adult hawksbills (Eretmochelys imbricata, Linnaeus 1766) in the eastern Pacific Ocean highlights shallow depth use by the species

Understanding the movement and dive behaviour of marine turtles directly informs spatial management strategies. Hawksbill turtles (Eretmochelys imbricata, Linnaeus 1766) are a globally endangered marine turtle species, with populations in the eastern Pacific Ocean identified as particularly threatened. To date, very little research on the dive behaviour of hawksbills has been conducted. Most studies have focused on juveniles in the Wider Caribbean region, and no dive behaviour has been described for hawksbills in the eastern Pacific. Using satellite-relayed dive loggers attached to five adult hawksbills, we analyzed dive trends and differences among individuals, movement phases and diel time periods, and compared our findings with those from hawksbills in other regions of the world. Our research indicates that adult hawksbills in the eastern Pacific predominantly use shallow waters (i.e. ≤ 10 m), with dives rarely occurring to depths > 20 m. Additionally, in contrast to previous research, we found similar dive behaviour across diel time periods, suggesting nocturnal activity may be more prevalent than previously believed. Despite some similarities in dive behaviour across individuals, individual variability was also evident. More research on adult hawksbills is urgently needed to increase our understanding of basic hawksbill ecology and behaviour, and improve management of this critically endangered species in the eastern Pacific Ocean.

► First dive study of hawksbills in the eastern Pacific Ocean.
► Overwhelming majority of dives occurred at depths ≤ 10 m.
► Similar dive behaviour across diel time periods.
► Shallower dives exhibited during foraging, compared to inter-nesting and migration phases.
► Important implications for hawksbills management.