Exercise warms adult leatherback turtles

Leatherback sea turtles (Dermochelys coriacea) can maintain body temperature (TB) up to 18 °C above that of the surrounding sea water (TW) which allows leatherbacks to enter cold temperate waters and have the largest global range of any reptile. Using a cylindrical model of a leatherback we investigated the extent to which heat production through variation of swim speed could be used in a leatherback's thermal strategy. Drag force of a full scale cast of a leatherback was measured in a low velocity wind tunnel to obtain an estimate of the metabolic cost needed to offset drag. Heat released in the core of a turtle as a byproduct of the metabolic cost of locomotion is conducted from the core of the turtle to the surrounding water through its insulation layer. By keeping insulation thickness constant, we highlight the effectiveness of swim speed in maintaining TB − TW. Our model, when tested against published data at a given TW, showed a close correlation between predicted and measured swimming speed at a given TB. We conclude that the ability to maintain a large TB − TW is an interplay between mass, insulation thickness and water temperature selection but behavioural control of swimming speed predominates.