crocodilians

Crocodilians are a group of large, semi-aquatic reptiles comprising the living families Alligatoridae (alligators and caimans), Crocodylidae (true crocodiles), and Gavialidae (gharials). They are among the closest living relatives of birds and dinosaurs, with a fossil record extending back more than 80 million years.

They inhabit tropical and subtropical regions of Africa, the Americas, Asia, and Australia, occupying rivers, wetlands, swamps, mangroves, and coastal areas, including brackish and saltwater habitats for some species.

Crocodilians have elongated snouts, powerful tails, and eyes and nostrils located on the top of the head for a semi-aquatic lifestyle. Their teeth are conical and frequently replaced. The skin bears osteoderms, or bony plates. They are ectothermic and possess a four-chambered heart with a vascular shunt that can adjust blood flow during dives.

They are carnivorous and opportunistic, feeding on fish, amphibians, reptiles, birds, and mammals, and will scavenge when available. They are typically ambush predators, relying on patience and a sudden bite. In many species, females guard nests and provide parental care; hatchlings may be carried to water by the mother.

Crocodilians reproduce by laying eggs; nests are usually built of vegetation or soil. Eggs incubate for several weeks to months, and incubation temperature influences hatchling sex. Some species exhibit extended parental care.

Many crocodilian species are threatened by habitat loss, hunting, and pollution. Conservation measures include protected areas, hunting restrictions, and captive breeding, with varying levels of success across regions.