The American Alligator sometimes referred to colloquially as a gator, is a large crocodilian endemic to the Southeastern United States. It is one of the two living species in the genus Alligator, within the family Alligatoridae. It is larger than the other extant alligator species, the Chinese alligator. The American alligator inhabits freshwater wetlands, such as marshes and cypress swamps from Texas to North Carolina. It is distinguished from the sympatric American crocodile by its broader snout, with overlapping jaws and darker coloration. It is less tolerant of seawater but is more tolerant of colder climates.
The American alligator is listed as Least Concern by the International Union for Conservation of Nature. Historially, hunting has decimated their population and it was listed as an endangered species by the Endangered Species Act of 1973. Subsequent conservation efforts have allowed their numbers to increase and the species was removed from the list in 1987. Alligators are now harvested for their skins and meat. The species is the official state reptile of three states: Florida, Louisiana and Mississippi.
American alligators typically range 4–4.5 m (13–15 ft) for adult males and under 3 m (9.8 ft) for adult females. There have been reports during the 19th and 20th centuries of larger males reaching 5–6 m (16–20 ft), although these are disputed. Adult males may weigh around 227 kg (500 lb) while females weigh around 91 kg (200 lb). Wild alligators range from long and slender to short and robust, possibly due to variations in factors like growth rate, diet and climate. Alligators have broad snouts, especially in captive individuals. When the jaws are closed, the edge of the upper jaws covers the lower teeth which fit into the jaws' depressions. Like the spectacled caiman, this species has a bony nasal ridge, though it is less prominent. Dorsally, adult alligators may be olive, brown, gray or black in color while their undersides are cream colored. The teeth number from 74–84.
Alligators inhabit swamps, streams, rivers, ponds and lakes. Females and juveniles are also found in Carolina Bays and other seasonal wetlands. While they prefer freshwater, alligators sometimes enter more brackish water. Alligators modify some wetland habitat, in flat areas such as the Everglades, by constructing small ponds known as "alligator holes". These create wetter or drier habitats for other organisms, such as plants, fish, invertabrates, amphibians, reptiles and mammals. In the limestone depressions of cypress swamps, alligator holes tend to be large and deep while those in marl prairies and rocky glades are usually small and shallow and those in peat depressions of ridge and slough wetlands are more variable. Man-made holes do not appear to have as large an effect. Alligators also may control the long term vegetation dynamics in wetlands by reducing the population of small mammals, particularly nutria, which may otherwise over-graze marsh vegetation. In this way, they provide a vital ecological service that may be important in reducing rates of coastal wetland losses in Louisiana.
The American alligator is considered the apex predator throughout its range. They are opportunists and their diet is determined largely by both the size and age of the predating alligator and the size and availability of prey. Most alligators will eat a wide variety of animals, including invertebrates, fish, birds, turtles, snakes, amphibians and mammals, in their life cycle. Hatchlings mostly feed on on invertebrates such as insects, larvae, snails, spiders, and worms. As they grow, alligators gradually move on to larger prey. Once an alligator reaches adulthood, any animal living in the water or coming to the water to drink is potential prey, due to the size and power of the alligator. However, most animals captured by alligators are considerable smaller than the alligator itself. Stomach contents show that, among native mammals, muskrats and raccoons are some of the most commonly eaten species. In Louisiana, where introduced nutria (a large aquatic rodent) are common, they are perhaps the most regular prey for adult alligators, although it is only larger adults alligators that commonly eat this species.
Other animals may occasionally be eaten, even large deer or feral wild boars, but these are not normally part of the diet. Occasionally, domestic animals, including dogs and calves, are taken as available but are secondary to wild and feral prey. Water birds, such as herons and egrets, storks and waterfowl, are taken when possible. Occasionally, unwary adult birds are grabbed and eaten by alligators, but most predation on bird occurs on unsteady fledgling birds in late summer as they attempt to make their first flights near the water's edge. Other prey, including snakes, lizards and various invertebrates are eaten occasionally by adults.