American Alligator

The **American alligator** (*Alligator mississippiensis*), sometimes referred to colloquially as a **gator** or **common alligator**, is a large crocodilian reptile endemic to the southeastern United States. It is one of two living species in the genus *Alligator* within the family Alligatoridae; it is larger than the other extant alligator species, the Chinese alligator. Adult male American alligators measure 3.4 to 4.6 m (11 to 15 ft) in length, and can weigh up to 453 kg (1,000 lb). Females are smaller, measuring around 3 m (9.8 ft). 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, and is less tolerant of saltwater but more tolerant of cooler climates than the American crocodile, which is found only in tropical climates.

American alligators are apex predators and consume fish, amphibians, reptiles, birds, and mammals. Hatchlings feed mostly on invertebrates. They play an important role as ecosystem engineers in wetland ecosystems through the creation of alligator holes, which provide both wet and dry habitats for other organisms. Throughout the year, but particularly during the breeding season, American alligators bellow to declare territory and locate suitable mates. Male American alligators use infrasound to attract females. Eggs are laid in a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water. Young are born with yellow bands around their bodies and are protected by their mother for up to one year.

The American alligator is listed as Least Concern by the International Union for Conservation of Nature. Historically, hunting had decimated their population, and the American alligator 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. American alligators are now harvested for their skins and meat. The species is the official state reptile of three states: Florida, Louisiana, and Mississippi.

## Description

The American alligator was first classified by French zoologist François Marie Daudin as *Crocodilus mississipiensis* in 1801. In 1807 Georges Cuvier created the genus *Alligator*; the American alligator shares this genus with the Chinese alligator. They are grouped in the family Alligatoridae with the caimans. The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator than to either the Nile crocodile or the gharial.

Members of this superfamily first arose in the late Cretaceous. *Leidyosuchus* of Alberta is the earliest known genus. Fossil alligatoroids have been found throughout Eurasia as land bridges across both the North Atlantic and the Bering Strait have connected North America to Eurasia during the Cretaceous, Paleogene, and Neogeneperiods. Alligators and caimans split in North America during the late Cretaceous and the latter reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period. The Chinese alligator likely descended from a lineage that crossed the Bering land bridge during the Neogene. The modern American alligator is well represented in the fossil record of the Pleistocene. 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. However, the full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.

In 2016, a Miocene fossil alligator's skull was found at Marion County, Florida. Unlike the other extinct alligator species of in the same genus, the fossil skull was virtually indistinguishable from that of the modern American alligator. This alligator and the American alligator are now considered to be sister taxa, meaning that the *Alligator mississippiensis* lineage has existed in North America for over 8 million years.

Domestic American alligators range from long and slender to short and robust, possibly due to variations in factors such as growth rate, diet, and climate. American alligators have broad snouts, especially in captive individuals. When the jaws are closed, the edges of the upper jaws cover the lower teeth which fit into the jaws' hollows. Like the spectacled caiman, this species has a bony nasal ridge, though it is less prominent. The teeth number 74–80. Dorsally, adult American alligators may be olive, brown, gray, or black in color, while their undersides are cream-colored.

Some American alligators are missing an inhibited gene for melanin, which makes them albino. These American alligators are extremely rare and almost impossible to find in the wild. They could only survive in captivity, as they are very vulnerable to the sun and predators.

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