American Alligator

Wild alligators range from long and slender to short and robust, possibly due to variations in factors such as growth rate, diet, and climate. 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' depressions. Like the spectacled caiman, this species has a bony nasal ridge, though it is less prominent.[8] The teeth number from 74–80.[8] Dorsally, adult alligators may be olive, brown, gray, or black in color, while their undersides are cream-colored.[9]
Some alligators are missing an inhibited gene for melanin, which makes them albino. These alligators are extremely rare and almost impossible to find in the wild. They could survive only in captivity, as they are very vulnerable to the sun and predators.[10]
Size[edit]
The American alligator is a fairly large species of crocodilian. As in all crocodilians, as opposed to many mammals where size eventually dimishes with old age, healthy alligators continue to grow throughout their lives and the oldest specimens are the largest. Very old, large male alligators reach an expected maximum size of 4.6 m (15 ft) in length, weighing up to 453 kg (999 lb), while females grow to a maximum of 3 m (9.8 ft).[11][12] On rare occasions, a large, old male may grow to an even greater length.[13][14] During the 19th and 20th centuries, larger males reaching 5 to 6 m (16 to 20 ft) have been reported.[8] The largest reported individual size was a male killed in 1890 on Marsh Island, Louisiana, and reportedly measured at 5.8 m (19 ft) in length, but no voucher specimen was available, since the alligator was left on a muddy bank after having been measured due to having been too massive to relocate.[14] If the size of this animal were correct, it would have weighed around 1,000 kg (2,200 lb). The largest alligator shot in Florida was 5.31 m (17.4 ft), as reported by the Everglades National Park.[15][16]
However, American alligators do not normally reach such extreme sizes. In mature males, size averages around 3.4 m (11 ft) in length, weighing slightly in excess of 227 kg (500 lb), while in smaller females, the mature size averages 2.6 m (8.5 ft), weighing slightly more than 91 kg (201 lb).[17][18] While noticeably sexual dimorphic in size, the sexual dimorphism of this species is relatively modest amongst crocodilians.[19] In the saltwater crocodile, for example, the females are only slightly larger at average (2.8 m (9.2 ft) in the crocodile, 2.6 m (8.5 ft) in the alligator) than female American alligators, but the mature males, at 4.3 to 5.2 m (14 to 17 ft) on average as opposed to 2.7 to 4 m (8.9 to 13.1 ft) expected in mature male alligators, are considerably bigger than male American alligators and at median are nearly twice as long as and at least four times as heavy as the female crocodiles of the same species.[20] Given that female alligators have relatively higher survival rates at an early age and a large percentage of given populations are comprised by immature or young breeding alligators, relatively few large mature males of the expected length of 3.4 m (11 ft) or more are typically seen.[21] Weight varies considerably depending on length, age, health, season and available food sources. Similar to many other reptiles than range expansively into temperate zones, American alligators from the northern end of their range, such as southern Arkansas, Alabama, and northern North Carolina, tend to grow to smaller sizes. The largest alligator caught in Alabama was 4.5 m (15 ft) in length, weighing 459 kg (1,012 lb). [22]

http://en.wikipedia.org/wiki/American_alligator