Alligators

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AMERICAN ALLIGATOR - Alligator mississippiensis

The American Alligator is a reptile and a member of the Crocodilia family.  There are only two members of the Crocodilia family that are native to the United States - the American Alligator and the American Crocodile.  There are 23 known species of Crocodilians that inhabit the Earth and only two species are alligators (the American Alligator and the very rare Chinese Alligator). Alligators are nocturnal creatures, hunting eating primarily from dusk until dawn, but they are also opportunistic feeders when it comes to eating, and if they are hungry, they will grab their prey regardless of time of day. In their habitat and range, alligators serve as a top predator in the food chain, feeding on the weak, diseased, and the unwary.  They help to maintain healthy prey populations and, as scavengers attracted to the dead and decomposing, they help to recycle nutrients into the food chain and help stop the spread of disease.

 

Their habitat consists of coastal marshes, large shallow lakes, swamps, ponds, creeks, and rivers. Alligators are equally at home in fresh or brackish water and have a high tolerance for poor water quality. Alligators will occasionally wander into the ocean or salt marshes for short periods of time to “cleanse” their skin and scales of leeches, bacteria, and other skin parasites or conditions. Captive alligators can have a life span of 50 to 80 years, but in the wild, alligators that live past 30 years are rare. Alligators can run faster than people over a short distance, usually at about 2-10 miles per hour.                                                                                                                 

 

Alligator Physiology

Alligators are ectothermic (cold-blooded) like all reptiles.  All activity, including feeding behavior, metabolic rate, and digestion is dependent upon external temperature.

Feeding behavior stops when water temperatures drop below about 60 degrees Fahrenheit.  All crocodilians need heat from the sun to activate digestive enzymes.  Cold temperatures can kill an alligator with a full stomach, as the food will rot instead of digest.

While it seems that alligators do nothing but lie in the sun on warm days, it is the need for warmth to facilitate digestion that drives this behavior. The dark skin of alligators quickly absorbs heat.  When they get too warm they return to the water.  In the summer, gators repeat this behavior several times a day.  Gators usually return to the water around dusk, when the air temperature begins to drop.  On cool windy days or on hot summer days, they remain in the water.

 

Courtship and Mating

Alligators are polygamous, meaning they will mate with more than one individual.

Spring is the season for courtship and mating. During this season, alligators can become very competitive which can occasionally turn violent.  Battles over territory can leave males wounded or dead.  During these challenges between males, the males will face off, glare at each other, hiss, and lash their tails back and forth.  Sometimes, the weaker male will concede and back off immediately.  Males that are about the same strength will usually stand their ground and fight.  When fighting, the males will grab onto each other with teeth and claws and roll each other through the water.  On land, they draw blood as they bite each other’s head, limbs, tail, and back.  Males can lose their legs and tails during such confrontations.  If the rival is killed and the surviving male is hungry, the survivor has been known to eat their victim.

 

Bellowing and Courtship

Alligators are the most vocal of all the crocodilians.  They will hiss, grunt, cough, growl, and bellow.  All of these sounds are part of a complex signaling system that allows alligators to communicate with one another.  The loud, deep, and long hiss is produced to be a warning that is emitted just prior to a defensive attack. Alligators have no vocal chords.  The males are able to bellow loudly by sucking air into their lungs and blowing it out in intermittent deep-toned roars.  This is done to attract a female and warn off other males in the area. While bellowing, the male alligator’s body inflates as he raises his head and tail out of the water.  He slowly waves his tail back and forth and puffs out his throat and begins to vibrate the air.  Right before they bellow, male alligators project an infrasonic signal through the water that causes vibrations in the ground and in nearby objects.  The low frequency vibrations travel great distances  through both air and water to announce the gators presence in the area.  The vibration is so strong, that it literally causes sparkling water droplets to leap off of the surface of the water.  This is called the “Water Dance”. Musically, the bellow of all male alligators is tuned to a B-flat tone. Along with the hormonal trigger, alligators bellow in response to thunder, sonic booms, and instruments that play on the B-flat key.  The bellowing chorus of a population of alligators most often occur during the spring when breeding groups gather together in close proximity to one another.  Bellowing usually occurs in the morning and late afternoon and can last from 10 minutes up to a half an hour and the sound can travel a great distance over water. Females also produce a single bellow that is usually more high pitched than the males. Males also usually other gestures to impress and win over females.  They will blow air bubbles underwater and make loud popping sounds by rapidly opening and closing their mouths as they slap their lower jaws against the surface of the water.  The males will also swish their tails back and forth rapidly in the water.  They perform these gestures to threaten and show dominance to other males and the courted female.

 

Reproduction

The reproductive cycle of crocodilians is the most advanced among reptiles.

Alligators are sexually dimorphic, meaning that males are larger than the females.  Males grow larger and faster than females. Both sexes lack secondary sexual characteristics, so there is really no way to accurately determine the sex of a gator be external features. Sexual maturity is determined by both size and age.  They are usually sexually mature at around six to ten years of age, or roughly six feet in length.  Growth rates vary depending on temperature and food availability.  In SC, which is in the northern portion of their range and which has a shorter growing season, female alligators can sometimes take up to eighteen years to reach sexual maturity. Females usually have small territories while a male’s territory can be as large as two miles. Between April and May, courtship and mating occurs. Within 3-4 weeks after mating, the females will move into secluded marsh areas to nest and will remain in that area until the following spring. Courtship can last for several hours, and it is thought to help synchronize both ovulation and spermatogenesis. Males generally court the female, but during a two week period of heightened fertility around the end of April and the beginning of May, females aggressively pursue the males.  She will gently push the male and nuzzle him around his head and neck ( the sides of which are loaded with sensitive touch receptors).  They then take turns rubbing and blowing bubbles for each other. Copulation usually only lasts two to three minutes, and after mating, the males and females have relatively little to do with each other. Only the females build and guard the nest and protect her offspring.

 

Nesting, Incubation, and Offspring

During late June and early July, females begin to nest by building a large mound of vegetation which will incubate the eggs as it decomposes.  The nest site is determined by the female.  Nests are usually about three feet high and about six feet in diameter. With her hind foot, the female digs a depression in the top of the nest and lays 20 to 50 eggs, about one every thirty seconds, in the egg chamber.  The egg chamber is then covered with more vegetation. Incubation lasts approximately 65 days during which the female remains very close to the nest to ward off predators. Most of the offspring hatch between mid-August and mid-September. They announce their readiness to hatch with squeaks and grunts that can be heard outside of the nest.  Their high pitched squeaks call the mother who then uncovers her hatchlings from the nest and carries them in her mouth down to the water. The hatchlings cut themselves out of their shells with a temporary egg tooth or caruncle that disappears shortly after hatching. Occasionally, the female will assist her offspring by cracking the egg shell for them gently between tongue and the top of her mouth At hatching, the young weigh about 2 ounces each and are about 8 inches long. Hatchlings have dark shin with yellow crossbands to assist in camouflaging themselves when trying to avoid heavy predation.  They are vulnerable to large fish, birds, bobcats, otters, snakes, turtles, raccoons and other alligators. As they mature, they will lose the yellow bands.  Eighty percent of the hatchlings will not survive to two years old. Once in the water, the hatchlings form a pod for protection under the watchful eye of the female. Female alligators are unique in the reptile world when it comes to the care and protection of their offspring.  She aggressively guards her nest and watches over them once they are hatched, often allowing them to rest on her back.  Alligators remain with their mothers for two years or more.