A Radiotelemetric Study of Heating and Cooling Rates in Unrestrained, Captive Crocodylus porosus

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Abstract
Like other reptiles, crocodiles use a combination of behavioral and physiological mechanisms to balance heat gain and loss. Changes in skin temperature precede changes in deep body temperature and closely parallel fluctuations in ambient temperature. The thermal time constant, τ, can be used to compare rates of heat exchange for both heating and cooling in step- or ramp-function conditions. Unrestrained crocodiles tend to avoid conditions of negative heat loading and accordingly prefer step-function heating and ramp-function cooling. In general, a crocodile can heat twice as fast as it cools. It is suspected that active cardiovascular control is an important factor in regulating the rate of heat exchange between a crocodile and its environment. The rate of heat exchange between a crocodile and its environment is directly dependent on its body mass. The prediction is made that thermostability may be possible for a sufficiently large crocodile.