In South Africa, Nile crocodiles are more easily observed in winter because of the extensive amount of time they spend basking at this time of year. More time is spent in water in overcast, rainy, or misty days. In the southern reaches of their range, as a response to dry, cool conditions that they cannot survive externally, crocodiles may dig and take refuge in tunnels and engage in aestivation. Pooley found in Royal Natal National Park that during aestivation, young crocodiles of total length would dig tunnels around in depth for most, some tunnels measuring more than , the longest there being . Crocodiles in aestivation are totally lethargic, entering a state similar to animals that hibernate. Only the largest individuals engaging in aestivation leave the burrow to sun on warmest days, otherwise these crocodiles rarely left their burrows. Aestivation has been recorded from May to August.