Diving behaviour of hawksbill turtles during the inter-nesting interval: Strategies to conserve energy
Hawksbill sea turtles (Eretmochelys imbricata) nesting in Barbados were outfitted with time-depth recorders (TDRs) with temperature sensors to investigate the form and patterns of diving behaviour during the inter-nesting interval (INI; average 14.7 days). All females, regardless of size, surfaced infrequently during dives of average 56 min duration, and the majority of dives (90%) were spent in the bottom phase at 15–25 m depths, which corresponded to the depth of benthic habitat at each location. Diving activity was highest while commuting to and from the nesting beach (about 1–2 days each way), with a level of quiescence during the intermediate period (i.e. the majority of the INI). Despite little thermal variation in seawater at this latitude (13.1°N), the length of the INI was influenced by ambient sea water temperature. Diving behaviour was consistent with females conserving energy reserves built up at foraging grounds prior to arrival at the nesting beach and minimising time spent in the water column away from safe refuge at night. The frequency of surfacing and the depths at which females spend most of their time varies between sites even within one species and may be crucial in managing the risks to animals temporarily residing offshore from important nesting beaches.