Crocodilians are found in over 90 countries and islands, generally in tropical and subtropical regions warm enough for successful reproduction. American and Chinese alligators, found in the highest latitudes of any species, do have a limited ability to survive seasonal freezing where deep water or shelter is available. Large adults can even endure being trapped in ice, as long as their internal organs do not freeze and their nostrils project above the surface.

Alligatoridae are restricted to North, Central, and South America, except for the Chinese alligator (A. sinensis), which occurs in eastern China. The stronghold of the Crocodylidae is Africa, India, and Asia, although a handful are found in the Americas. The single member of Gavialidae is found in India and adjacent countries. Estuarine crocodiles have the widest distribution (India to Vanuatu), although Nile crocodiles cover the greatest area (most of Africa and Madagascar). Spectacled caimans (Caiman crocodilus) number in the millions and are the most numerous throughout Central and South America. Introduced populations of certain species, particularly caimans, are established outside their natural ranges.

Crocodilians favor freshwater habitats, although several members of Crocodylidae tolerate higher salinity. Estuarine (also known as saltwater) crocodiles live in freshwater tidal rivers, hypersaline creeks, and along coastlines, and can travel at sea. Their ability to excrete excess salt through lingual salt

American crocodiles (Crocodylus acutus) along the river bank in the Everglades National Park. (Photo by Guido Cozzi. Bruce Coleman, Inc. Reproduced by pemission.)

glands and produce concentrated urine make this possible. All species frequent freshwater and low-salinity areas where available, including tidal rivers, freshwater marshes, and both natural and artificial lakes and pools. Distribution is influenced by the density and diversity of prey, available nesting habitat, shelter for juveniles and adults, thermal conditions, seasonal changes, and competition between species. Temporary range extensions have occurred when competition from one species over another has been reduced due to hunting, etc.

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