[5] It is also found in river systems, but tends to prefer salinity, resulting in the species congregating in brackish lakes, mangrove swamps, lagoons, cays, and small islands.

Upon hearing of a "big old gator" in Arch Creek at the head of Biscayne Bay, Hornaday and his companions searched for it and reported: In a few hours, we got sight of him, out on the bank in a saw-grass wallow.

[22] Phylogenetic evidence supports Crocodylus diverging from its closest recent relative, the extinct Voay of Madagascar, around 25 million years ago, near the Oligocene/Miocene boundary.

[31] Adults have a uniform grayish-green coloration with white or yellow undersides, while juveniles have dark cross-banding on the tail and back.

With extensive conservation efforts underway, there appears to be an increase in the number of large American crocodiles in Florida, some of the largest reportedly exceeding 4 m (13 ft 1 in) in length.

On the other hand, another specimen measuring 3.95 m (13 ft 0 in) in total length was found to have weighed 500 kg (1,100 lb)[41] An individual named "Papillon" was considered to be one of the largest American crocodiles in captivity.

They inhabit waters such as mangrove swamps, river mouths, fresh waters, and salt lakes, and can even be found at sea, hence their wide distribution throughout southern Florida,[48] the Greater Antilles (excluding Puerto Rico and Isla de la Juventud, where they are replaced by the introduced spectacled caiman[49]), Martinique, southern Mexico (including the Yucatán Peninsula), Central America, and the South American countries of Colombia, Peru, Venezuela (including on Margarita Island), and Ecuador.

The crocodile likely originated in the Zapata Swamp of Cuba (the only place where these wild hybrids exist, and where the two species are sympatric), and swam to the Yucatán Peninsula.

There have been reports of American crocodiles in Trinidad, however, those sightings are thought to have arisen due to the accidental translocation of the animal outside of its normal range.

[54] The American crocodile's saline tolerance may have allowed it to inhabit limited portions of the United States, particularly southern Florida.

[55] Within the United States, the American crocodile's distribution is generally limited to the southern tip of Florida, though at least two have been found as far north as the Tampa Bay area.

However, at the end of the 19th century, hunting them for their leather became a cottage industry in South Florida, and beginning in 1910, habitat destruction commenced on a massive scale, with the construction of a railroad designed to connect the mainland with the Keys.

[63] As of 2020, further population seems to be expanding south to reclaim former habitat in the Florida Keys, where numbers are multiplying quickly, and old records indicate they once inhabited mangroves as far north as Tampa Bay.

[26] American crocodiles are apex predators, and any aquatic or terrestrial animal they encounter in freshwater, riparian and coastal saltwater habitats is potential prey.

Prey species have ranged in size from the insects taken by young American crocodiles to full-grown cattle taken by large adults, and can include various birds, mammals, turtles, snakes, lizards, smaller crocodilians, echinoderms, insects, arachnids, crabs, other crustaceans, snails, other molluscs, frogs, fish, and occasionally carrion and fruits.

[70] Elsewhere, aquatic insects and their larvae and snails are near the top of the food list for American crocodiles at this very early age.

[71] In Florida, bass, tarpon and especially mullet, large crabs, snakes, mammals that habit the riparian and coastal regions of the Everglades, such as opossums and raccoons appeared to be the primary prey of American crocodiles.

[75] In Costa Rica, American crocodiles have been recorded hunting and killing adult female olive ridley sea turtles (Lepidochelys olivacea) when they come to nest around beaches.

[82] American crocodiles breed in late fall or early winter, engaging in drawn-out mating ceremonies in which males emit low-frequency bellows to attract females.

Body size is more important than age in determining reproductive capabilities, and females reach sexual maturity at a length of about 2.8 m (9 ft 2 in).

In February or March, gravid females will begin to create nests of sand, mud, and dead vegetation along the water's edge.

Because sex determination is temperature-dependent in crocodilians, slight aberrations in temperature may result in all-male or all-female clutches, which would possibly harm the health of the population.

But in spite of these precautions, American crocodile eggs sometimes fall prey to raccoons (arguably the most virulent natural predator of crocodilian nests in the Americas), coatis, foxes, skunks or other scavenging mammals (including coyotes in Mexico and American black bears in southern Florida), as well as large predatory ants, crabs and vultures.

During the hatching process, when the young American crocodiles are most vulnerable to predation, they will instinctively call out in soft, grunt-like croaks.

Most of them will not survive, being preyed upon by several types of raptorial birds, other reptiles, and large fishes (e.g., barred catfish, Atlantic tarpons, common snook and lemon sharks, boa constrictors, black spiny-tailed iguanas and spectacled caimans).

[2] On March 20, 2007, the United States Fish and Wildlife Service declassified the American crocodile as an endangered species, changing its status to "threatened".

[89] Because of hide hunting, pollution, loss of habitat, and commercial farming, the American crocodile is endangered in parts of its range.

[90] In southern Florida, about two-thirds of American crocodile deaths are attributed to road collisions, about 10% to intentional killing, and only about 5% to natural causes.

[91] In recent years in Jamaica there has been rampant poaching of the species for their meat and there has been a significant population drop compounded by the lack of action by the government.

[36][95] In May 2007, two instances occurred within one week of children being attacked and killed by American crocodiles—one in Mexico just south of Puerto Vallarta and one in Costa Rica.