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Alligator, Gator, American alligator, Florida alligator, Mississippi alligator, Louisiana alligator.

Alligator mississippiensis

What do they look like?

The average size for an adult female is just under 3 meters (9.8 feet), while the adult male usually falls between 4 and 4.5 meters (13 to 14.7 feet). American alligators reaching lengths of 5-6 meters (16 to 20 feet) have been reported in the past, but there have been no recent recordings equaling those lengths. (Britton, 1999; Ross, 1989)

American alligators have very short legs, but they are still able to run very quickly over short distances. The two front legs each have 5 toes, and the two back legs each have four webbed toes. The snout of America alligators is also very important. It is much broader for those animals kept in zoos and parks than for those that live in the wild. This is because of the animal's diet. (Britton, 1999)

Alligators have nostrils at the end of their snouts. This makes it easy for the alligator to breath while it is under water. All it has to do it stick the tip of it's snout into the air. During the winter alligators do this and let the top half of their body to freeze in the ice. (Britton, 1999)

Both males and females have an "armored" body with a muscular flat tail used for swimming. The skin is so tough because of hard bony plates called scutes. Adults have an olive brown or black color with a creamy white underside. Young alligators look different only because they are smaller and have yellow stripes on their tails. American alligators usually have silverish eyes. (Britton, 1999; Ross, 1989)

  • Sexual Dimorphism
  • male larger
  • Average mass
    150000 g
    5286.34 oz
    AnAge
  • Range length
    3 to 4.5 m
    9.84 to 14.76 ft
  • Average basal metabolic rate
    0.1539 W
    AnAge

Where do they live?

American alligators are found 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. (Britton, 1999)

What kind of habitat do they need?

American alligators are usually found in freshwater, slow-moving rivers. They are also found in swamps, marshes, and lakes. Unlike some crocodile species, American alligators can only live in salt water for a short time. (Britton, 1999; Ross, 1989)

American alligators are also known to modify their enivironment by creating burrows. These are created using both snout and tail and are used for shelter and hibernation during freezing temperatures. If the water they live in dries out, alligators will swim or walk to other bodies of water, sometimes even taking shelter in swimming pools. (Britton, 1999)

How do they grow?

The temperature at which American alligator eggs develop determines their sex. Those eggs which are hatched in temperatures ranging from 90 to 93 degrees Fahrenheit turn out to be male, while those in temperatures from 82 to 86 degrees Fehrenheit end up being female. Intermediate temperature ranges have proven to yield a mix of both male and females. After hatching, alligators can grow rapidly, espectially during the first four years of life, averaging over 1 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. (; Ross, 1989)

  • Development - Life Cycle
  • temperature sex determination

How do they reproduce?

Breeding takes place during the night, in shallow waters. Females usually start the courtship process. Attracting a mate often involves rubbing, touching, blowing bubbles, and making sounds. The sounds made by males create bubbles and ripples in the water. To test eachothers strength, both male and female will often try to push each other under water. (; Ross, 1989)

Alligators are polygynous. That means that each male mates with many females. During breeding season males alligators are very territorial, and they will defend their area against other males by headramming or attacking one another with open jaws. (; Ross, 1989)

Both males and females reach sexual maturity when they are about six feet long, a length attained at about 10 to 12 years, earlier for males than females. Courtship starts in April, with mating occuring in early May. After mating has taken place, the female builds a nest of vegetation. Then, around late June and early July, the female lays 35 to 50 eggs. Some females have been reported as laying up to 88 eggs. The eggs are then covered with the vegetation nest through the 65-day incubation period. (Britton, 1999; )

Around the end of August the young alligators begin to make high pitched noises from inside the eggs. The alligators then break free from their eggs. They are about 6-8 inches long when they are born. Most of these baby alligators will be eaten by predators before they reach one year of age. Mother alligators, though, stay with their young for a few months, and occasionally, a few years. (Britton, 1999; )

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • oviparous
  • How often does reproduction occur?
    American alligators breed once yearly.
  • Breeding season
    Breeding occurs in early May, with egg laying occuring in late June and early July.
  • Range number of offspring
    35 to 88
  • Range age at sexual or reproductive maturity (female)
    10 to 12 years
  • Range age at sexual or reproductive maturity (male)
    10 to 12 years

Males 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 bring them to water after hatching. During the first year or so she will defend her hatchlings from predators. After the first year, the female leaves her young to tend to new hatchlings of the next breeding season. ()

  • Parental Investment
  • pre-weaning/fledging
    • protecting
      • female

How long do they live?

While there are currently no methods for determining the age of an alligator while still alive, it is known that those in the wild tend to live to between 35 and 50 year, while those in captive generally live longer, around 65-80 years. Factors which can lead to earlier mortality include successful predation early in life and hunting by humans. ()

  • Typical lifespan
    Status: wild
    35 to 50 years
  • Typical lifespan
    Status: captivity
    65 to 80 years

How do they behave?

Young alligators remain in the area where they are hatched and are generally a social species when young. This method of group living is associated with greater protection from predators. Adults do not display such close knit bonds, however, they do tend to associate loosly in social groups. When forced to live in tighter areas as a result of drought, though, these animals tend to ignore each other. (Britton, 1999; Levy, 1991; Ross, 1989)

One interesting aspect of alligator biology is that even though they don't hibernate, they undergo periods of dormancy when the weather becomes cold. They may excavate a cave in a waterway and leave a portion of it above water during this time. In areas where water level fluctuates, alligators 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 hot or cold weather. (Britton, 1999; Levy, 1991)

Perhaps the most interesting aspect of alligator behavior is its means of locomotion. Besides swimming, American alligators walk, run, and crawl. Most often they will use a "high walk". In this walk alligators keep their legs almost directly beneath them, as opposed to most reptiles which keep their legs to the sides at a diagonal. This "high walk" results in greater elevation, allowing alligators to almost entirely lift their tales up off of the ground. (Ross, 1989)

When alligators wish to increase speed they diagonally opposite limbs move forward almost simultaneously. This allows for faster movement, but it also decreases the animal's stability. When the eqilibrium is lost an alligator begins moving in a new way, moving its limbs out to the sides and crashing onto its chest. In this manner an alligator quickly crawls along. This method of movement is most useful when going down steep shorelines into the water. (Ross, 1989)

Home Range

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. (Britton, 1999; Levy, 1991)

How do they communicate with each other?

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. Alligators also emit sounds called chumpfs. These are cough like purrs made during courting. (; Levy, 1991; Ross, 1989)

Other communication during mating season includes non-verbal forms such as lifting the head out of the water to show honorable intentions, headslapping by males as a sign of aggression to ward off intruders, and perhaps most notably, the virbrations, bubbles, and ripples seen in the water as a result of subaudible noises.

What do they eat?

Alligators are basically carnivores, but they eat more than just meat, feeding on anything from sticks to fishing lures to aluminum cans. Mostly, they consume fish, turtles, snakes, and small mammals. When they are young they feed on insects, snails, and small fish. (Britton, 1999; Levy, 1991)

Alligators hunt primarily in the water at night, snapping up small prey and swallowing it whole. Large prey are dragged under water, drowned and then devoured in pieces. Alligators have also been known to hold food in their mouth until it deteriorates enough to swallow. They also have a specialized valve in the throat called a glottis, which allows them to capture prey underwater. ()

With regards to hunting animals on land, alligators are usually considered idle hunters, waiting offshore for unsuspecting prey to drink at the water's edge. With this approach an alligator is likely to grab the drinking animal's head, slowly pulling it underwater until it drowns. In this way alligators exert minimal energy in capturing prey.

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • eggs
  • insects
  • mollusks
  • Plant Foods
  • wood, bark, or stems

What eats them and how do they avoid being eaten?

The first few years of a hatchlings life are the most dangerous, as anything that can eat a small alligator will. Snakes, wading birds, osprey, raccoons, otters, large bass, garfish, even larger alligators will feed upon young alligators. Once the alligator reaches about 4 feet, its only real predator is man. Extremely thick skin protected by bony plates called scutes prevent harm from most attacks. It is this skin, though, which attracts man to alligators. It is commercially used for the creation of wallets, purses, boots, and other textiles. (; Ross, 1989)

What roles do they have in the ecosystem?

American alligators have proven to be an important part of the environment, and therefor, are considered by many to be a "keystone" species. Not only do they control populations of prey species, they also create peat and "alligator holes" which are invaluable to other species. Red-bellied turtles, for example, incubates its own eggs in old alligator nests. Alligators also are good indicators of environmental factors, such as toxin levels. Increased levels of mercury have been found in recent blood samples. (Britton, 1999)

Do they cause problems?

Since the alligator will feed on almost anything, they pose a 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. (University of Florida)

How do they interact with us?

Alligators are hunted mostly for their skin, but also they are hunted for their meat. Today, there is a multimillion dollar industry in which alligators are raised in captivity for the production of their meat and skin. Also, alligators are a tourist attraction, especially in Florida.

  • Ways that people benefit from these animals:
  • food
  • body parts are source of valuable material
  • ecotourism

Are they endangered?

American alligators are listed as threatened by the federal government because they are similar in appearance to American crocodiles (Crocodylus acutus). American crocodiles are endangered and the government does not want hunters to confuse the two species. Hunting is allowed in some states, but is is heavily controlled.

Contributors

Lauren Pajerski (author), Undergraduate Research Opportunity Program, University of Michigan.

Benjamin Schechter (author), University of Michigan-Ann Arbor, Robin Street (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

animals that have little or no ability to regulate their body temperature, body temperatures fluctuate with the temperature of their environment, often referred to as 'cold-blooded'.

keystone species

this species is important to many other species. If it is wiped out in a place, many other species will be wiped out too.

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

threatened

describes species which may become endangered. See glossary entries for IUCN categories and Endangered Species Act.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Levy, Charles K. 1991. Crocodiles and Alligators. The Apple Press. London. Pages 8-22, 59.

National Audobon Society Field Guide to North American Reptiles and Amphibians; 1994.

Britton, A. 1999. "Alligator mississippiensis in the Crocodilians, Natural History and Conservation" (On-line). Accessed 31 March 2000 at http://www.flmnh.ufl.edu/cnhc/csp_amis.htm.

Levy, C. 1991. Crocodiles and Alligators.. London: The Apple Press.

Ross, C. 1989. Crocodiles and Alligators. New York, New York: Facts on File, Inc..

 
University of Michigan Museum of ZoologyNational Science Foundation

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Schechter, B. and R. Street 2000. "Alligator mississippiensis" (On-line), Animal Diversity Web. Accessed April 24, 2014 at http://www.biokids.umich.edu/accounts/Alligator_mississippiensis/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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