Body temperature and basking behaviour of Nile crocodiles (Crocodylus niloticus) during winter

The ability to thermoregulate in reptilians is often through behavioural modification. We investigated body temperature (Tb) patterns during winter in the amphibious Nile crocodile (Crocodylus niloticus) and its relationship to basking behaviour at the St. Lucia Crocodile Centre, St. Lucia, South Africa. It was found that crocodiles had no daily plateaus in Tb but rather continuous oscillations in Tb within a range of mean minimum Tb 18.8–19.6 °C to mean maximum Tb 26.9–29.2 °C. Crocodile Tb increased during the day, usually after 10:00 irrespective of body size. Behavioural data showed that the crocodiles usually left the water to bask around 10:00. It is suggested that basking behaviour is important for elevating Tb rather than attaining a preferred Tb. The increased Tb may allow them to perform optimally when they return to water. The basking occurrence has management implications as it suggests that the best time to conduct aerial censuses of the St. Lucia crocodiles is during winter after 10:00 when most of the individuals are basking and hence most easily seen.