Crocodiles in this genus are believed to have changed very little in the past 20 million years. They may even have been around during the extinction of the dinosaurs. These large, aquatic reptiles tend to congregate in the slow-moving rivers and swamps of Africa, Asia, Australia and the Americas - the perfect places from which to ambush prey. Many populations of the 13 living species are now endangered and protected, having come under pressure from hunting and habitat loss. It is the larger species, such as the Nile and saltwater crocodiles, that pose a real threat to humans.

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