Sea turtles are among the largest extant reptiles. These highly active marine animals consistently have body temperatures above those of their surroundings, allowing them to migrate to colder waters without greatly increasing the risk of hypothermic stunning. There is no one term that suffices to describe thermoregulatory strategies of sea turtles.

Sea turtles are gigantotherms, as they benefit from a large thermal inertia due to a large body size with a low surface area to volume ratio. Sea turtles are poikilothermic; their body temperature varies. They are endothermic in that they have a high aerobic capacity and an elevated metabolic rate that produces heat used to raise their body temperature. They benefit from regional blood flow and countercurrent exchangers to maintain this elevated temperature. But, like many classic ectotherms, sea turtles use their surroundings to regulate body temperature. In addition to heating endothermically, they bask or choose warmer waters in order to raise their temperatures. Sea turtles cool their bodies ectothermically, as they do not have any physiological mechanisms at their disposal to dump heat to their surroundings when they are in danger of overheating. Such mechanisms did not develop because they can swim into deeper, cooler waters if the need arises.

Though sea turtles are ancestral, they have a complex thermoregulatory biology that cannot be defined as purely endothermic or ectothermic.

Green sea turtle, photo courtesy of Jeffrey Seminoff


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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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