Cold-blooded divers: temperature-dependent dive performance in the wild hawksbill turtle Eretmochelys imbricata

Abstract

Sea turtles are diving ectotherms that are influenced by the temperature of the ambient water, although swimming activity can temper this influence via increased body temperatures enhanced by the thermal inertia of these large animals. We successfully equipped 3 nesting hawksbill turtles Eretmochelys imbricata with time-depth recorders (TDRs) to monitor water temperature and dive depth over the duration of the re-migration interval between 2 successive nesting seasons. Data sets for up to 22 mo were obtained, showing fluctuations in water temperature over the seasons. Nocturnal dive behaviour of the turtles at their foraging grounds revealed an increase in dive duration with decreasing water temperatures in winter. A model is provided to estimate dive duration for the range of temperatures experienced by this species in the wild. The data on vertical velocity during ascent and descent phases as a parameter for activity failed to show thermal dependence. It is concluded that changes in water temperature have an effect on the behavioural ecology of hawksbill turtles.

Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders

“…Dives made during the hours of darkness were longer and less variable than those undertaken during daylight. Taken together, these observations suggest periods of decreased activity at night, which has been reported for other juvenile and adult hawksbill turtles (Van Dam & Diez 1996, 1997, Storch et al 2005, Houghton et al 2008, Blumenthal et al 2009b). However, there was no diel difference in dive depths, highlighting the influence of a depthlimited environment on habitat utilisation behaviour.…”

The behaviour of a hawksbill turtle data-logged during the passage of hurricane Georges through the Caribbean

“…It is well known that undisturbed hawksbill turtles routinely conduct long dives (van Dam and Diez 1997;Storch et al 2005), and this same behaviour is seen in other marine turtle species such as the green turtle (Chelonia mydas) (Hays et al 2002(Hays et al , 2004b. The shortened dive duration during the hurricane can be interpreted as an indication of increased metabolism resulting from active swimming behaviour.…”

“…Deployments of data loggers onto hawksbill turtles at this site are described in detail by Storch et al (2005). Data readings of all channels were taken at intervals of 15 s in non-volatile 1 MB memory.…”

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

“…For diurnal time periods, it is likely that dive behaviour is related to foraging and feeding, activities that occur almost exclusively during the day (Blumenthal et al, 2009;Okuyama et al, 2010;Storch et al, 2005;van Dam and Diez, 1997). Surface times have been found to be longer between feeding bouts as turtles recover from extended foraging dives (Blumenthal et al, 2009).…”