Thermoregulation in Tortoises

Abstract

ALTHOUGH reptiles in a laboratory cage may show feeble powers of thermoregulation, it is now known that, when active in natural conditions, their body temperature is often regulated by behavioural means at a thermal level higher than that of many mammals¹. Tortoises are no exception and sun themselves when the air is cool. Experiments on young desert tortoises, Testudo sulcata Miller (= T. calcarata Schn.), have shown that water loss by evaporation increases greatly in dry air at temperatures above 40°–41° C. At ambient temperatures of 55° C the body temperature rises rapidly to about 40.5° C, at which level it is maintained by copious salivation which wets the head, neck and front legs. Although they do not usually take water when supplied with green food, these tortoises drink deeply after such experiments.