Some aspects of thermoregulation in three species of southern African tortoise

Abstract

Behavioral and physiological thermoregulation were studied in Chersina angulata, Homopus areolatus and Geochelone pardalis. Response to thermal gradient suggests it to be of greatest significance in H. areolatus. Physiological thermoregulation was studied in terms of individual capacities to control thermal conductance. All 3 spp. showed definite capacities to thermoregulate by altering conductance. H. areolatus appears to possess the greatest physiological control of conductance and has a higher maximum preferred temperature than the other 2 spp. studied. Large specimens of G. pardalis show little physiological control of heat flux; this decreases with increasing size. C. angulata has a greater degree of control over conductance than G. pardalis. Size alone can not explain all the different thermoregulatory characteristics. The need for a holistic theory of physiology and ecology of thermoregulation in tortoises is demonstrated.