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 extant species in the genus Alligator within the family Alligatoridae; it is larger than the only other living alligator species, the Chinese alligator.
Adult male American alligators measure 3.4 to 4.6 m (11.2 to 15.1 ft) in length, and can weigh up to 453 kg (999 lb). Females are smaller, measuring 2.6 to 3 m (8.5 to 9.8 ft) in length. The American alligator inhabits freshwater wetlands, such as marshes and cypress swamps from Texas to southeastern and coastal 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, in particular 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 conservation status of 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 endangered status in 1987. The species is the official state reptile of three states: Florida, Louisiana, and Mississippi.
Description & appearance
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. The American alligator is a relatively large species of crocodilian. On average, it is the second-largest species in the family Alligatoridae, behind only the black caiman. Weight varies considerably depending on length, age, health, season, and available food sources. Similar to many other reptiles that 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 reach smaller sizes. 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. As with all crocodilians, and as opposed to many mammals where size eventually diminishes with old age, healthy American alligators may continue to grow throughout their lives and the oldest specimens are the largest. Very old, large male American alligators reach an expected maximum size up to 4.6 m (15 ft 1 in) in length and weighing up to 453 kg (999 lb), while females reach a maximum of 3 m (9 ft 10 in). On rare occasions, a large, old male may grow to an even greater length.
During the 19th and 20th centuries, larger males reaching 5 to 6 m (16 ft 5 in to 19 ft 8 in) have been reported. The largest reported individual size was a male killed in 1890 on Marsh Island, Louisiana, and reportedly measured at 5.84 m (19 ft 2 in) in length, but no voucher specimen was available, since the American alligator was left on a muddy bank after having been measured due to having been too massive to relocate. If the size of this animal was correct, it would have weighed about 1,000 kg (2,200 lb). In Arkansas, a man killed an American alligator that was 4.04 m (13 ft 3 in) and 626 kg (1,380 lb). The largest American alligator ever killed in Florida was 5.31 m (17 ft 5 in), as reported by the Everglades National Park. The largest American alligator scientifically verified in Florida for the period from 1977 to 1993 was reportedly 4.23 m (13 ft 11 in) and weighed 473 kg (1,043 lb), although another specimen (size estimated from skull) may have measured 4.54 m (14 ft 11 in). A specimen that was 4.8 m (15 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.
Dorsally, adult American alligators may be olive, brown, gray, or black. However, they are on average one of the most darkly colored modern crocodilians (although other alligatorid family members are also fairly dark), and can be reliably be distinguished by color via their more blackish dorsal scales against crocodiles. Meanwhile, their undersides are cream-colored. Some American alligators are missing or have 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.
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; 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. No significant difference is noted between the bite forces of male and female American alligators of equal size.
When on land, an American alligator moves either by sprawling or walking, the latter involving the reptile lifting its belly off the ground. The sprawling of American alligators and other crocodylians is not similar to that of salamanders and lizards, being similar to walking. Therefore, the two forms of land locomotion can be termed the "low walk" and the "high walk". Unlike most other land vertebrates, American alligators increase their speed through the distal rather than proximal ends of their limbs. In the water, American alligators swim like fish, moving their pelvic regions and tails from side to side. During respiration, air flow is unidirectional, looping through the lungs during inhalation and exhalation; the American alligator's abdominal muscles can alter the position of the lungs within the torso, thus shifting the center of buoyancy, which allows the American alligator to dive, rise, and roll within the water.
Distribution & habitat
They inhabit swamps, streams, rivers, ponds, and lakes. A lone American alligator was spotted for over 10 years living in a river north of Atlanta, Georgia. Females and juveniles are also found in Carolina Bays and other seasonal wetlands. While they prefer fresh water, American alligators may sometimes wander into brackish water, but are less tolerant of salt water than crocodiles, as the salt glands on their tongues do not function. One study of 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. Both sexes may den underneath banks or clumps of trees during the winter. Food
The teeth number 74–80. As American alligators grow and develop, the morphology of their teeth and jaws change significantly. Juveniles have small, needle-like teeth that become much more robust and narrow snouts that become more broad as the individuals develop. These morphological changes correspond to shifts in the alligators' diets, from smaller prey items such as fish and insects to larger prey items such as turtles, birds, and other large vertebrates. 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. Reproduction
The breeding season begins in the spring. On spring nights, American alligators gather in large numbers for group courtship, in the aforementioned "water dances". The female builds a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water.
After the female lays her 20 to 50 white eggs, about the size of a goose egg, she covers them with more vegetation, which heats as it decays, helping to keep the eggs warm. This differs from Nile crocodiles, which lay their eggs in pits. The temperature at which American alligator eggs develop determines their sex (see temperature-dependent sex determination). Those eggs hatched at a temperature of 93 °F (34 °C) or more become males, while those at a temperature of 86 °F (30 °C ) or lower become female. The nests built on levees are warmer, thus produce males, while the cooler nests of wet marsh produce females. The female remains near the nest throughout the 65-day incubation period, protecting it from intruders. When the young begin to hatch — their "yelping" calls can sometimes even be heard just before hatching commences — the mother quickly digs them out and carries them to the water in her mouth, as some other crocodilian species are known to do.
The young are tiny replicas of adults, with a series of yellow bands around their bodies that serve as camouflage. Hatchlings gather into pods and are guarded by their mother and keep in contact with her through their "yelping" vocalizations. Young American alligators eat small fish, frogs, crayfish, and insects. They are preyed on by large fish, birds, raccoons, and adult American alligators. Mother American alligators eventually become more aggressive towards their young, which encourages them to disperse. Young alligators grow 3–8 in (7.6–20.3 cm) a year and reach adulthood at 6 ft (1.8 m).