The average size for an adult female is just under 3 meters (9.8 feet), while the adult male usually falls between 4 and 4.5 meters (13 to 14.7 feet). American alligators reaching lengths of 5-6 meters (16 to 20 feet) have been reported in the past, but there have been no recent recordings equaling those lengths.
Legs of American alligators are characteristically short, though capable of carrying the animal at a gallop. The front legs have five toes while the back legs have only four. The snout of this alligator species is also distinct, being significantly broader for those in captive, mainly due to a difference in diet.
Nostrils at the end of the snout allow for breathing while the alligator is otherwise fully submerged beneath the water's surface. During times of hibernation, alligators keep these nostrils just above the water's surface, allowing the top part of the body to freeze in ice. The large fourth tooth in the lower jaw fits into a socket in the upper jaw and is not visible when the mouth is closed.
Both males and females have an "armored" body with a muscular flat tail, used in propelling the animal forward while swimming. The skin on their back is armored with embedded bony plates called osteoderms or scutes. Adult males and females have an olive brown or black color with a creamy white underside. The young can be distinguished from adults because they have bright yellow stripes on their tails. Eye color of American alligators is generally silverish.
Range length: 3 to 4.5 m.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger
Average mass: 150000 g.
Average basal metabolic rate: 0.1539 W.