An alligator, or colloquially gator, is a large reptile in the genus Alligator of the family Alligatoridae in the order Crocodilia. The two Extant taxon species are the American alligator ( A. mississippiensis) and the Chinese alligator ( A. sinensis). Additionally, several extinct species of alligator are known from fossil remains. Alligators first appeared during the late Eocene epoch about 37 million years ago.
The term "alligator" is likely an anglicized form of el lagarto, Spanish language for "the lizard", which early Spanish explorers and settlers in Florida called the alligator.
the Southeastern United States |
eastern China |
Adult alligators are black or dark olive-brown with white undersides, while juveniles have bright yellow or whitish stripes which sharply contrast against their dark hides, providing them additional camouflage amongst reeds and wetland grasses.
Alligators commonly live up to 50 years, but there have been examples of alligators living over 70. One of the oldest recorded alligator lives was that of Saturn, an American alligator who was hatched in 1936 in Mississippi and spent nearly a decade in Germany before spending the majority of his life at the Moscow Zoo, where he died at the age of 83 or 84 on 22 May 2020. Another one of the oldest lives on record is that of Muja, an American alligator who was brought as an adult specimen to the Belgrade Zoo in Serbia from Germany in 1937. Although no valid records exist about his date of birth, as of 2012, he was in his 80s and possibly the oldest alligator living in captivity.
American alligators are found in the southeast United States: all of Florida and Louisiana; the southern parts of Georgia, Alabama, and Mississippi; coastal South Carolina and North Carolina; East Texas, the southeast corner of Oklahoma, and the southern tip of Arkansas. Louisiana has the largest alligator population.2005 Scholastic Book of World Records The majority of American alligators inhabit Florida and Louisiana, with over a million alligators in each state. Southern Florida is the only place where both alligators and live side by side."Trappers catch crocodile in Lake Tarpon", Tampa Bay Times, July 12, 2013
American alligators live in freshwater environments, such as , , , , , and , as well as in brackish water.Dundee, H. A., and D. A. Rossman. 1989. The Amphibians and Reptiles of Louisiana. Baton Rouge: Louisiana State University Press. When they construct alligator holes in the wetlands, they increase plant diversity and provide habitat for other animals during droughts.Craighead, F. C., Sr. (1968). The role of the alligator in shaping plant communities and maintaining wildlife in the southern Everglades. The Florida Naturalist, 41, 2–7, 69–74. They are, therefore, considered an important species for maintaining ecological diversity in wetlands.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Chapter 4. Farther west, in Louisiana, heavy grazing by and is causing severe damage to coastal wetlands. Large alligators feed extensively on nutrias, and provide a vital ecological service by reducing nutria numbers.
The Chinese alligator currently is found in only the Yangtze River valley and parts of adjacent provinces and is extremely endangered, with only a few dozen believed to be left in the wild. Far more Chinese alligators live in zoos around the world than can be found in the wild. Rockefeller Wildlife Refuge in southern Louisiana has several in captivity in an attempt to preserve the species. Zoo Miami in Florida also has a breeding pair of Chinese alligators.
Alligators move on land by two forms of locomotion, referred to as "sprawl" and "high walk". The sprawl is a forward movement with the belly making contact with the ground and is used to transition to "high walk" or to slither over wet substrate into water. The high walk is an up-on-four-limbs forward motion used for overland travel with the belly well up from the ground.Reilly & Elias, Locomotion In Alligator Mississippiensis: Kinematic Effects Of Speed And Posture and Their Relevance To The Sprawling-to-Erect Paradigm The Journal of Experimental Biology 201, 2559–2574 (1998) Alligators have also been observed to rise up and balance on their hind legs and semi-step forward as part of a forward or upward lunge. However, they can not walk on their hind legs.
Although the alligator has a heavy body and a slow metabolism, it is capable of short bursts of speed, especially in very short lunges. Alligators' main prey are smaller animals they can kill and eat with a single bite. They may kill larger prey by grabbing it and dragging it into the water to drown. Alligators consume food that cannot be eaten in one bite by allowing it to rot or by biting and then performing a "death roll", spinning or convulsing wildly until bite-sized chunks are torn off. Critical to the alligator's ability to initiate a death roll, the tail must flex to a significant angle relative to its body. An alligator with an immobilized tail cannot perform a death roll.
Most of the muscle in an alligator's jaw evolved to bite and grip prey. The muscles that close the jaws are powerful, but the muscles for opening their jaws are weak. As a result, an adult human can hold an alligator's jaws shut bare-handed. It is common to use several wraps of duct tape to prevent an adult alligator from opening its jaws when being handled or transported.
Alligators are generally timid towards humans and tend to walk or swim away if one approaches. This may encourage people to approach alligators and their nests, which can provoke the animals into attacking. In Florida, feeding wild alligators at any time is illegal. If fed, the alligators will eventually lose their fear of humans and will learn to associate humans with food.
In summer, the female builds a nest of vegetation where the decomposition of the vegetation provides the heat needed to incubate the eggs. The sex of the offspring is determined by the temperature in the nest and is fixed within seven to 21 days of the start of incubation. Incubation temperatures of or lower produce a clutch of females; those of or higher produce entirely males. Nests constructed on leaves are hotter than those constructed on wet marsh, so the former tend to produce males and the latter, females. The baby alligator's egg tooth helps it get out of its egg during hatching time. The natural sex ratio at hatching is five females to one male. Females hatched from eggs incubated at weigh significantly more than males hatched from eggs incubated at . The mother defends the nest from predators and assists the hatchlings to water. She will provide protection to the young for about a year if they remain in the area. Adult alligators regularly cannibalize younger individuals, though estimates of the rate of cannibalism vary widely. In the past, immediately following the outlawing of alligator hunting, populations rebounded quickly due to the suppressed number of adults preying upon juveniles, increasing survival among the young alligators.
The alligator has a similar digestive system to that of the crocodile, with minor differences in morphology and enzyme activity. Alligators have a two-part stomach, with the first smaller portion containing Gastrolith. It is believed this portion of the stomach serves a similar function as it does in the gizzard of some species of birds, to aid in digestion. The gastroliths work to grind up the meal as alligators will take large bites or swallow smaller prey whole. This process makes digestion and nutrient absorption easier once the food reaches the second portion of the stomach. Once an alligator's meal has been processed it will move on to the second portion of the stomach which is highly acidic. The acidity of the stomach has been observed to increase once digestion begins. This is due to the increase in Carbon dioxide concentration of the blood, resulting from the right to left shunting of the alligators heart. The right to left shunt of the heart in alligators means the circulatory system will recirculate blood through the body instead of back to the lungs. The re-circulation of blood leads to higher CO2 concentration as well as lower oxygen affinity. There is evidence to suggest that there is increased blood flow diverted to the stomach during digestion to facilitate an increase in CO2 concentration which aids in increasing gastric acid secretions during digestion. The alligator's metabolism will also increase after a meal by up to four times its basal metabolic rate. Alligators also have highly folded mucosa in the lining of the intestines to further aid in the absorption of nutrients. The folds result in greater surface area for the nutrients to be absorbed through.
Alligators also have complex Microbiome that are not fully understood yet, but can be attributed to both benefits and costs to the animal. These microorganisms can be found in the high surface area of the mucosa folds of the intestines, as well as throughout the digestive tract. Benefits include better total health and stronger immune system. However alligators are still vulnerable to microbial infections despite the immune boost from other microbiota.
During brumation the process of digestion experiences changes due to the fasting most alligators experience during these periods of inactivity. Alligators that go long enough without a meal during brumation will begin a process called autophagy, where the animal begins to consume its fat reserves to maintain its body weight until it can acquire a sufficient meal. There is also fluctuation in the level of bacterial taxa populations in the alligator's microbial community between seasons which helps the alligator cope with different rates of feeding and activity.
Like other crocodilians, alligators have an armor of bony scutes. The dermal bones are highly vascularised and aid in calcium balance, both to neutralize acids while the animal cannot breathe underwater and to provide calcium for eggshell formation.
Alligators have muscular, flat tails that propel them while swimming.
The two kinds of white alligators are albino and Leucism. These alligators are practically impossible to find in the wild. They could survive only in captivity and are few in number. The Aquarium of the Americas in New Orleans has leucistic alligators found in a Louisiana swamp in 1987.
Alligator meat is also consumed by humans.
File:Florida-Everglades National Park-3.jpg|Alligator in the Everglades National Park
File:Alligator Canberra Zoo.jpg|Alligator in the Canberra Zoo in Australia
File:Gator in Lousiana bayou swim.jpg|Gator in Louisiana bayou swims
File:Gator in Lousiana bayou eats.jpg|Gator in Louisiana bayou eats
File:Juvenile alligator II.jpg|Juvenile alligator found in Everglades National Park
Behavior
Diet
Reproduction
Anatomy
Human uses
Differences from crocodiles
Image gallery of extant species
See also
External links
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