National Zoo – American Alligator

By FNZ
August 25, 2009

The average size for an adult female American alligator is 8.2 feet (2.6 m), and the average size for a male is 11.2 feet (3.4 m). Exceptionally large males can reach a weight of nearly half a ton or 1,000 pounds.

Both males and females have an “armored” body with a muscular flat tail. The skin on the back is armored with embedded bony plates called osteoderms or scutes. They have four short legs; the front legs have five toes while the back legs have four toes.

Alligators have a long snout with upward facing nostrils at the end; this lets them breathe while the rest of the body is underwater. The young can be distinguished from adults by the bright yellow stripes on the tail; adults have dark stripes on the tail.

Distinguishing Alligators from Crocodiles

The easiest way to distinguish an alligator from a crocodile is by looking at the teeth. The large fourth tooth in the lower jaw of an alligator fits into a socket in the upper jaw and is not visible when the mouth is closed. This does not happen in crocodiles. Alligators have between 74 and 80 teeth in their mouth at a time. As teeth wear down they are replaced. An alligator can go through 2,000 to 3,000 teeth in a lifetime.

Female alligators usually remain in a small area. The males occupy areas larger than two square miles. Both males and females extend their ranges during the courting and breeding season. Young alligators remain in the area where they are hatched and where they are protected by their mother. After two to three years, they leave that area in search of food, or are driven out by larger alligators.

One interesting aspect of alligator biology is that they undergo periods of dormancy when the weather is cold. They excavate a depression called a “gator hole” along a waterway and use it during dormancy.

In areas where the water level fluctuates, alligators dig themselves into hollows in the mud, which fill with water. These tunnels are often as long as 65 feet (20 m) and provide protection during extreme hot or cold weather. Many other animals also use these burrows after they are abandoned by their creators.

Distribution and Habitat

The American alligator is found from North Carolina to the Rio Grande in Texas.

Alligators are usually found in freshwater, in slow-moving rivers. They are also found in swamps, marshes, and lakes. They can tolerate salt water for only brief periods because they do not have salt glands.

Diet in the Wild
Crocodilians are carnivorous. They have very strong jaws that can crack a turtle shell. They eat fish, snails and other invertebrates, birds, frogs, and mammals that come to the water’s edge. They use their sharp teeth to seize and hold prey. Small prey is swallowed whole. If the prey is large, crocodilians shake it apart into smaller, manageable pieces. If it is very large, crocodilians bite it, then spin on the long axis of their bodies to tear off easily swallowed pieces.

Zoo Diet
At the Zoo, the American alligator is fed rats and occasionally chickens and rabbits.

Reproduction
Both males and females reach sexual maturity when they are about six feet (1.8 m) long, a length attained at about ten to 12 years. Breeding takes place during the night, in shallow waters. Males roar to attract females and to ward off other males. The male circles the female and mounts. Courtship starts in April, with mating occurring in early May.

After mating, the female builds a nest of vegetation. The nest measures seven to ten feet (2.1 to 3 m) in diameter and is two to three feet (.6 to .9 m) high. Then, around late June and early July, the female lays 35 to 50 eggs. Some females lay up to 90 eggs. The eggs are then covered with the vegetation nest through the 65-day incubation period. The sex of the juveniles is determined by the temperature of the nest: above 93° F (33.8° C) all are male, below 86° F (30° C) all are female, and temperatures in between will produce both sexes. Red-bellied sliders may sometimes deposit their eggs in alligator nests.

Toward the end of August, the young alligators begin to make high-pitched noises from inside of the egg. This lets the mother know that it is time to remove the nesting material. When the alligator hatches it measures about six to eight inches (15 to 20 cm). Newly hatched alligators live in small groups called “pods.” Eighty percent of young alligators fall victim to birds and raccoons. Other predators include bobcats, otters, snakes, large bass, and larger alligators. Females aggressively defend their young during these first few years. Crocodilians are unusual among reptiles in providing maternal care to their young. The juveniles grow about a foot a year. Maturity is reached during the sixth year.

Life Span
American alligators may live to about 50 years in the wild. After it is four feet long, an alligator is safe from predators except humans and occasionally other alligators.

Status
Once on the verge of extinction, the American alligator has made a remarkable recovery. Due to strict conservation measures and extensive research, it is no longer endangered except in scattered areas of its range. However, the American alligator is listed as threatened on the U.S. Endangered Species List because it is very similar in appearance to the American crocodile, which is endangered, and hunters are likely to confuse the two species. Hunting is allowed in some states, but it is heavily controlled. The greatest threat is currently destruction of habitat; this includes water management systems and increased levels of mercury and dioxins in the water.

Because alligators will feed on almost anything, they pose a mild threat to humans. In Florida, where there is the greatest alligator population, there were five deaths to alligator attacks from 1973 to 1990. Dogs and other pets are also sometimes killed.

Fun Facts
The alligator became the official state reptile of Florida in 1987.

The alligator family includes the American and Chinese alligators and all caimans. Spanish sailors visiting the New World thought the unfamiliar alligator was a huge lizard. In Spanish, el lagarto means the lizard. English sailors took the name as allagarter and in time it has become alligator.

Alligators are hunted mostly for their skins, but also they are hunted for meat. Today, there is a multi-million dollar industry in which alligators are raised in captivity for the production of meat and skin. Also, alligators are a tourist attraction, especially in Florida, where visitors enjoy feeding them.

Taxonomy
Order: Crocodylia
Family: Alligatoridae
Genus/species: Alligator mississippiensis

Editor’s Note: For more information, including references, see the Animal Diversity Web account for this species, here: Animal Diversity Web

All or part of this information was provided by the Animal Diversity Web and Museum of Zoology of the University of Michigan.
It appears here with their permission. The original author of this information was Benjamin Schechter and Robin Street.

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Source: National Zoo