American alligators are found in the south eastern parts of the United States from the southern Virginia-North Carolina border, along the Atlantic coast to Florida and along the Gulf of Mexico as far west as the Rio Grande in Texas.
American alligators are usually found in freshwater swamps, marshes, rivers, lakes, and occasionally smaller bodies of water. They can also tolerate moderate amounts of salinity, but only for short periods of time due to their lack of buccal glands.
Alligators are carnivores preying on fish, turtles, snakes, and small mammals. When they are young they feed on insects, snails, and small fish. Alligators hunt primarily in the water at night, snapping up small prey and swallowing it whole. Large prey are dragged under water and devoured in pieces.
The first few years of a hatchling’s life are the most dangerous because many different types of animals will prey on them. Snakes, wading birds, osprey, raccoons, otters, large bass, garfish, and even larger alligators will prey on young alligators. Once an alligator reaches about 4 feet in length its only real predators are humans. Humans have hunted alligators for their hides to make wallets, purses, boots, and other textiles.
The average size for an adult female alligator is about 9 feet, while the adult male alligator usually falls between 13 to 15 feet long. American alligators reaching lengths of 16 to 20 feet have occasionally been reported.
Alligators have an “armored” body with embedded bony plates called osteoderms or scutes. Alligators are well adapted for life in water having an extremely muscular tail that is used in propelling the animal forward while swimming. Their nostrils are at the end of their snout allowing for breathing while the body of the alligator is fully submerged beneath the water’s surface.
Alligator courtship starts in April, with mating occurring in early May. After mating has taken place, the female builds a nest of vegetation. Then, around late June and early July, the female usually lays between 35 and 50 eggs. The eggs are covered with vegetation for a 65-day incubation period. The temperature at which American alligator eggs develop determines their sex. Eggs that are incubated in temperatures ranging from 90 to 93 degrees Fahrenheit become males, while eggs incubating at temperatures from 82 to 86 degrees Fahrenheit become females. Intermediate temperature ranges give a mix of both male and females. After hatching, alligators can grow rapidly, especially during the first four years of life, averaging about one foot of growth for each year of life. Both sexes reach sexual maturity at around 6 feet in length, however, this occurs earlier in males because they reach this length sooner than females. Young alligators make high-pitched calls from inside of the egg. These calls tell the mother that it is time to remove the nesting material, and the six to eight inch alligator is hatched. Male alligators provide no parental care, and parental care by the female is limited to the first year of life. She is responsible for removing any vegetation covering the nest when her young are ready to hatch, and she will often carry her young to water after hatching. During the first year or so she will defend her babies from predators. After the first year, the female leaves her young to tend to new hatchlings of the next breeding season.
In the wild alligators tend to live between 35 and 50 years, while those in captivity generally live longer, around 65-80 years and possibly longer. Factors that can lead to earlier mortality include predation early in life and hunting by humans.
Young alligators remain in the area where they are hatched and generally stay together while they are young. This tendency towards group living is associated with greater protection from predators. Adults do not display such close-knit bonds and tend to congregate loosely in social groups. When forced to congregate in smaller areas because of drought, these animals tend to tolerate each other. One interesting aspect of alligator biology is that even though they don’t hibernate, they undergo periods of dormancy when the weather becomes cold. Alligators often dig themselves into hollows in the mud, which fill with water. These tunnels are often as long as 65 feet and provide protection during extreme cold, or even hot, weather.
Female alligators usually remain in a small area. The males occupy areas greater than two square miles. Both males and females extend their ranges during the courting and breeding season.
American alligators are the most vocal of all crocodilians, and communication begins early in life, while alligators are still in eggs. When they are ready to hatch, the young will make high-pitched whining noises. Alligators commonly bellow and roar at one another. The bellow is loud and throaty, and can be heard from up to 165 yards away. Female alligators also emit sounds called chumpfs that are cough like purrs made during courting. Other forms of communication during mating season includes non-vocal gestures such as lifting the head out of the water to show good intentions, head slapping by males to display aggression towards intruders, and sub audible sounds such as vibrations, bubbles, and ripples that can be seen in the water.
The easiest and quickest way to determine the difference between an alligator and crocodile is to compare the snouts of the two. Alligators have a relatively broad snout whereas crocodiles have a snout that is much narrower. Think of the alligator as having a “U” shaped snout and crocodiles having a “V” shaped snout. Another difference between the two is with the placement of teeth. In alligators, the upper jaw is larger than their lower jaw and 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. In crocodiles, the upper jaw and lower jaw are approximately the same width. As a result, the large fourth tooth in the lower jaw fits outside the upper jaw and is easily visible. In general, alligators tend to prefer fresh water whereas crocodiles tend to prefer salt water. These differences are not strict rules and each may venture outside of their preferred water type for short periods of time.
American alligators are an important part of the environment and are therefore considered by many to be a “keystone” species. Not only do they control populations of prey species, they also create “alligator holes” that are used by other animals. For example, red-bellied turtles sometimes incubate their own eggs in old alligator nests. Alligators can be used as indicators of environmental factors, such as toxin levels. Mercury levels have been studied in the blood samples of alligators.
The American alligator is listed as threatened by the federal government because it is similar in appearance to the endangered American crocodile and identity of the two may be confused. Since the American crocodile is endangered, the government does not want hunters to mistake the two different types of animals. Hunting is allowed in some states, but is highly controlled.
References Pajerski, L., B. Schechter and R. Street. 2000. “Alligator mississippiensis” (On-line), Animal Diversity Web. Accessed December 10, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Alligator_mississippiensis.html.