In-Water Observations of the Diving Behaviour of Immature Hawksbill Turtles, Eretmochelys imbricata, on a Coral Reef at D'Arros Island, Republic of Seychelles

The diving behavior of immature hawksbill turtles (Eretmochelys imbricata) was recorded by means of direct in-water observations during a period of 8 months over 4 years on a coral reef at D'Arros Island in the Seychelles. For 4 turtles that had become habituated, detailed behavioral observations were recorded and quantified during 148 contact hours during which 187 turtle dives were documented. Mean dive depth and duration were 8.2 m and 27.4 minutes, respectively. Surfacing intervals lasted on average 81.5 seconds and the mean number of breaths was 6.6 per surface interval. Dive duration was positively correlated with dive depth. On average, larger turtles conducted longer dives than smaller turtles and spent more time at the surface. Immature hawksbills at D'Arros averaged longer surface intervals and took more breaths than did those reported at other sites. We attribute this, at least in part, to the increased energy demands required to excavate cryptic food items at D'Arros. Although average foraging dives in this and other studies tended to be shallow (< 15 m) and short (< 30 minutes), the turtles are capable of significantly deeper and longer dives. We propose that immature hawksbills forage well below their physiological dive limits and do not strive to maximize their bottom times.