Some aspects of thermoregulation in three species of southern African tortoise

Abstract

Behavioural and physiological thermoregulation were studied in Chersina angulata, Homopus areolatus and Geochelone pardalis. Results on behavioural thermoregulation (response to thermal gradient) suggest it to be of greatest significance in H. areolatus. Physiological thermoregulation was studied in terms of individual capacities to control thermal conductance. All three species showed definite capacities to thermo- regulate by altering conductance. H. areolatus appears to possess greatest physiological control of conductance and has a higher maximum preferred temperature than the other two species studied. Large specimens of G. pardalis show little physiological control of heat flux and this decreases with increasing size. C. angulata has a greater degree of control over conductance than G. pardalis. It is concluded that size alone can not explain all the different thermoregulatory characteristics. The study demonstrates the need for a holistic theory of physiology and ecology of thermoregulation in tort...