[5][6][7][8][9] The American alligator inhabits subtropical and tropical freshwater wetlands, such as marshes and cypress swamps, from southern Texas to North Carolina.

[17] In 2016, a Late Miocene fossil skull of an alligator, dating to approximately seven or eight million years ago, was discovered in Marion County, Florida.

[1] The alligator's full mitochondrial genome was sequenced in the 1990s, and it suggests the animal evolved at a rate similar to mammals and greater than birds and most cold-blooded vertebrates.

[19] Domestic American alligators range from long and slender to short and robust, possibly in response to variations in factors such as growth rate, diet, and climate.

Large adult American alligators tend to be relatively robust and bulky compared to other similar-length crocodilians; for example, captive males measuring 3 to 4 m (9 ft 10 in to 13 ft 1 in) were found to weigh 200 to 350 kg (440 to 770 lb), although captive specimens may outweigh wild specimens due to lack of hunting behavior and other stressors.

[21] A specimen that was 4.5 m (14 ft 9 in) long and weighed 458.8 kg (1,011.5 lb) is the largest American alligator killed in Alabama and has been declared the SCI world record in 2014.

[52] There is a common belief stated throughout reptilian literature that crocodilians, including the American alligator, exhibit indeterminate growth, meaning the animal continues to grow for the duration of its life.

[61] Adult American alligators held the record as having the strongest laboratory-measured bite of any living animal, measured at up to 13,172 N (1,343.2 kgf; 2,961 lbf).

This experiment had not been, at the time of the paper published, replicated in any other crocodilians, and the same laboratory was able to measure a greater bite force of 16,414 N (1,673.8 kgf; 3,690 lbf) in saltwater crocodiles;[62][63] notwithstanding this very high biting force, the muscles opening the American alligator's jaw are quite weak, and the jaws can be held closed by hand or tape when an American alligator is captured.

Historically, hunting and habitat loss have severely affected American alligator populations throughout their range, and whether the species would survive was in doubt.

[3] They inhabit swamps, streams, rivers, ponds, and lakes as well as wetland prairies interspersed with shallow open water and canals with associated levees.

[84] One study of American alligators in north-central Florida found the males preferred open lake water during the spring, while females used both swampy and open-water areas.

During summer, males still preferred open water, while females remained in the swamps to construct their nests and lay their eggs.

[50] In some areas of their range, American alligators are an unusual example of urban wildlife; golf courses are often favored by the species due to an abundance of water and a frequent supply of prey animals such as fish and birds.

[88] When the water begins to freeze, American alligators go into a period of brumation; they stick their snouts through the surface, which allows them to breathe above the ice,[83] and they can remain in this state for several days.

By balancing sticks and branches on their heads, American alligators are able to lure birds looking for suitable nesting material to kill and consume.

[96] This strategy has been documented in two Florida zoos occurring multiple times a day in peak nesting season and in some parks in Louisiana.

Adult American alligators also spend considerable time hunting on land, up to 160 feet (50 m) from water, ambushing terrestrial animals on trailsides and road shoulders.

Most American alligators eat a wide variety of animals, including invertebrates, fish, birds, turtles, snakes, amphibians, and mammals.

[27] A few examples of animals consumed are largemouth bass, spotted gar, freshwater pearl mussels, American green tree frogs, yellow mud turtles, cottonmouths, common moorhens, and feral wild boars.

[106] If an American alligator's primary food resource is not available, it will sometimes feed on carrion and non-prey items such as rocks and artificial objects, like bottle caps.

[118] The discovery of this unexpected part of the American alligator diet further reveals that they may be responsible for spreading seeds from the fruit they consume across their habitat.

[122] The diet of adult American alligators from central Florida lakes is dominated by fish, but the species is highly opportunistic based upon local availability.

[124] In East Texas, diets were diverse and adult American alligators took mammals, reptiles, amphibians, and invertebrates (e.g. snails) in often equal measure as they did fish.

[125] An American alligator is able to abduct and adduct the vocal folds of its larynx, but not to elongate or shorten them; yet in spite of this, it can modulate fundamental frequency very well.

[128] The American alligator can perform specific vocalizations to declare territory, signal distress, threaten competitors, and locate suitable mates.

Both males and females bellow loudly by sucking air into their lungs and blowing it out in intermittent, deep-toned roars to attract mates and declare territory.

[134] Observers of large bellowing choruses have noted they are often felt more than they are heard due to the intense infrasound emitted by males.

[136] A study conducted in the 1980s at an alligator farm showed that homosexual courtship is common, with two-thirds of the recorded instances of sexual behaviour having been between two males.

American alligators prevent predatory mammals from reaching island-based rookeries and in return eat spilled food and birds that fall from their nests.