CLASS: Reptilia
ORDER: Crocodilia
FAMILY: Alligatoridae
GENUS & SPECIES: Alligator mississipiensis
CLASSIFICATION: Order Crocodilia is comprised of 3 families: Alligatoridae – American and Chinese alligators and caimans. Crocodylidae – Crocodiles, and Gavialidae – gavials.
RANGE:
Fresh to slightly brackish waters of coastal marshes, swamps, rivers, lakes, ponds, and man-made canals from North Carolina south to the Florida Keys, and west to eastern Texas. A suitable water source is required for feeding, social organization, reproduction and temperature regulation. The land adjacent to the water source must provide adequate vegetation for shade and shelter as well as areas for basking.
PHYSICAL DESCRIPTION:
All crocodilians have a four-chambered heart, a single penis, a non protrusible tongue, and scutes reinforced by bony plates in the back and tail regions. Alligatos and caimans general have broader, rounder snouts than crocodiles. Gavials have very slender pointed snouts and teeth which are longer and more slender in shape than in any other crocodilian. The well-known grinning expression of the crocodile with closed jaw is caused by interlocking upper and lower teeth and an enlarged 4th tooth in the lower jaw, which fits into a notch in the upper jaw and can be seen pointing upwards almost like a tusk. The teeth of the alligator and caiman are less visible, the lower teeth fitting inside the upper row. The enlarged 4th tooth fits into a pit in the upper jaw, concealed when the mouth is closed.
Coloration:
All species have counter-shading, being dark above and light underneath. The ventral color Is some shade of cream or yellow. The dorsal color is some shade of olive drab to brown. The dorsal coloration is often masked by algal growth.
DIET:
Insects, crustaceans, fish, frogs, snakes, waterfowl, and small mammals. Adults may eat dogs, cattle and other large mammals. Indiscriminate feeders; will take live prey or scavenge. Nonfood items, called gastroliths (stomach stones), are ingested and retained. Biologists disagree as to whether they function as ballast or aid in digestion.
BEHAVIOR:
Less aggressive than crocodiles. Bellowing is engaged in by both sexes and signals the beginning of courtship and mating in April. Males battle and victors establish territories in which they have priority access to females. Females guard nest sites against predators. Before hatching, the young are capable of vocalizing a high-pitched “erk” sound. Females respond to these vocalizations by opening the nest mound, carrying some young to water in her mouth and luring others from nest by vocalizations. Adults, other than the mother, will also respond to distress calls of the young. Maternal care is also exhibited by caimans and crocodiles.
Alligators do not chew; teeth are used for seizing, crushing and positioning prey. If prey is too large to swallow, the alligator swiftly rotates its body in a longitudinal spin until prey is dismembered. ‘Gators are inactive during the winter, especially in colder areas, where it winters in a water-filled “gator hole” or in a tunnel.
ADAPTATION:
The alligator is adapted for a predominately aquatic existence. Eyes, ears, and nostrils are positioned on top of the head, enabling it to see, hear, and breath when almost totally submerged.
The large eyes provide improved nocturnal vision and have well developed upper and lower eyelids and a nictitating membrane. The pupil closes down to a slit in daylight. Ears and nostrils can be closed when the animal is under water. All crocodilians are equipped with a secondary plate which runs the length of the muzzle.
Air is carried through the nasal cavities above the secondary plate and enters the throat behind a valve which seals off the throat from the mouth cavity. Since it lacks fleshy lips to seal out water, the valve enables the alligator to breath when almost entirely submerged and to open its jaws under water (to catch prey) without flooding its respiratory system.
Digits (5 forelimbs. 4 hind limbs) are webbed. When swimming the motive power is supplied by the muscular, laterally compressed tail. Limbs are used as rudders. The tail is also a powerful weapon of defense.
BREEDING & GROWTH:
20-60 eggs laid in center of nest (5′-7′ at base, 2′-3′ high) constructed by female from mud and vegetation, using both hind and forelimbs. Incubation 60-70 days. Outer shell of egg cracks and young slit the tough inner membrane with the caruncle on the tip of the snout. Hatchlings average 8″ long and are black with yellow bars. Grow one foot per year for the first 6 years. Growth slows after this period. Adult length for females is 6-8 feet, the male is 10-14 feet. Live to be 55 years old.
Eggs and young are extremely vulnerable to predation by raccoons, bears, otters, turtles, fish and herons. Probably only 10-20% survive the first 3 years. Adults have no natural enemies and are preyed upon only by man. Alligators play a crucial role in the life of the swamp. In areas of fluctuating water levels, the “gator holes” dredged by the alligators are often the last source of moisture during droughts, providing water for land animals as well as for fish, amphibians and aquatic invertebrates.
STATUS:
In this century the hunting of adults for their hides and capturing of young to sell as pets so drastically reduced populations that the American alligator was listed as an endangered species in 1967. In 1969 a federal law was passed making interstate shipment of alligators and skins taken in violation of state or federal law a federal offense. Under state and federal protection the alligator began a slow recovery in some areas.
In 1975 the IUCN reclassified the American alligator as recovered. In January, 1977, the U.S. Department of Interior listed the alligator as threatened over most of its range. This new status legalized the killing of alligators in “defense of human life” and the selling of hides so obtained. Human populations have expanded into alligator habitats in recent years, and complaints from residents in these areas are frequent. Florida will now permit licensed hunters to shoot “nuisance” alligators and sell their hides. In 1972, Louisiana began permitting annual controlled hunting for hides in 3 parishes (counties). If large males are killed, renewed hunting in Florida and Louisiana may disrupt the alligators’ male-dominated social structure during breeding, depriving populations of potentially important genetic contributions.
