We determined diurnal and seasonal patterns of body temperature (T(b)) in Crocodylus johnstoni in the wild by monitoring T(b) and behavior of 15 crocodiles, as well as measuring water, air and ground temperatures, and solar radiation. Two fundamentally different diurnal patterns of T(b) occurred. One (pattern A) was similar to that described as typical for thermoregulating heliothermic reptiles, in that crocodiles shuttled between basking on land and cooling in water so that T(b) formed a plateau elevated above water temperature (Tw) during the day. In the other (pattern B), crocodiles did not leave die water, and T(b) equalled T(w) throughout the day. Some crocodiles showed either pattern A or pattern B throughout the year, and some behaved differently at different seasons. The preferred body temperature range (PBTR) of those crocodiles that thermoregulated for all or most of the year changed seasonally, parallelling seasonal changes in T(w). The midpoint of the PBTR changed from approximately 29 C to 33 C, winter to summer. Intraspecific aggression prevented some crocodiles from thermoregulating effectively, and their PBTR was significantly lower when experiencing aggression from other crocodiles, compared with when undisturbed.
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Seebacher et al. (1997) studied this question.
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