or even semi-desert but can also acclimate to well-wooded swamps, extensively wooded riparian zones, waterways of other woodlands and the perimeter of forests. In Madagascar, the remnant population of Nile crocodiles has adapted to living within caves. Nile crocodiles may make use of ephemeral watering holes on occasion. Although not a regular sea-going species as is the American crocodile, and especially the saltwater crocodile, the Nile crocodile possesses salt glands like all true crocodiles (i.e., excluding alligators and caimans), and does on occasion enter coastal and even marine waters. They have been known to enter the sea in some areas, with one specimen having been recorded off St. Lucia Bay in 1917. Invasive potential Nile crocodiles have been recently captured in South Florida, though no signs that the population is reproducing in the wild have been found. Genetic studies of Nile crocodiles captured in the wild in Florida have revealed that the specimens are all closely related to each other, suggesting a single source of the introduction. This source remains unclear, as their genetics do not match samples collected from captives at various zoos and theme parks in Florida. When compared to Nile crocodiles from their native Africa, the Florida wild specimens are most closely related to South African Nile crocodiles. It is unknown how many Nile crocodiles are currently at large in Florida. The animals likely were either brought there to be released or are escapees. Behaviour Generally, Nile crocodiles are relatively inert creatures, as are most crocodilians and other large, cold-blooded creatures. More than half of the crocodiles observed by Cott (1961), if not disturbed, spent the hours from 9:00 a.m. to 4:00 p.m. continuously basking with their jaws open if conditions were sunny. If their jaws are bound together in the extreme midday heat, Nile crocodiles may easily die from overheating. Although they can remain practically motionless for hours on end, whether basking or sitting in shallows, Nile crocodiles are said to be constantly aware of their surroundings and aware of the presence of other animals. However, mouth-gaping (while essential to thermoregulation) may also serve as a threat display to other crocodiles. For example, some specimens have been observed mouth-gaping at night, when overheating is not a risk. In Lake Turkana, crocodiles rarely bask at all through the day, unlike crocodiles from most other areas, for unknown reasons, usually sitting motionless partially exposed at the surface in