Basking
Basking is intentional exposure to solar radiation in order to increase body temperature. Most reptiles, including many species of water dwelling turtle, bask. In sea turtles, basking is typically restricted to floating near the surface of the water, allowing part of the carapace to breach the surface (Spotila and Standora, 1985). Sea turtles cannot emerge completely or even mostly from the water like other water-dwelling turtles because there are no objects in the ocean that extend above its surface. This constraint affects the way sea turtles bask in the ocean.

Green turtles have been observed basking on land. Terrestrial basking occurs in response to cool ocean temperatures, which are usually coupled with steady winds that prevent the turtles from overheating. Turtles also flip sand on their carapaces with their flippers to avoid hyperthermia when basking. Terrestrial basking in green turtles is most often seen in females during the nesting season (Spotila and Standora, 1985), but it occurs only sporadically (Boyer, 1965). Its frequency is not enough to establish it as an influential thermoregulatory strategy (Hochscheid, et al, 2002).

In order for basking to occur in sea turtles, the benefits must outweigh the costs. Costs include an inability to forage and potential cooling of the carapace due to wind. A sea turtle benefits from basking if solar radiation warms its carapace and the surrounding water, thus raising the its core body temperature. Other water-dwelling turtles benefit from basking because drying out decreases the incidence of parasites. Drying influences only green turtle terrestrial basking, but there is no proof that it reduces parasite infestation. In general, warming is more important that drying in basking (Boyer, 1965).

That small speck is a basking green turtle!

Opinions on the significance of basking in sea turtles vary. It occurs, but not as often as in non-marine water-dwelling turtles, and its importance to thermoregulation is debated. Most likely, the other manners in which a sea turtle thermoregulates are more important to the maintenance of an elevated body temperature.

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This web site was completed by Katie Fitzpatrick in partial fulfillment of the requirements for Dr. Michael Dorcas's Biology 312, Animal Physiology, at Davidson College in Fall Semester 2005.

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Please direct all comments and questions to Katie Fitzpatrick at kafitzpatrick@davidson.edu