An alligator, or colloquially gator, is a large reptile in the genus Alligator of the family Alligatoridae in the order Crocodilia. The two extant 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 , Spanish for "the lizard", which early Spanish explorers and settlers in Florida called the alligator. Early English spellings of the name included allagarta and alagarto.Morgan, G. S., Richard, F., & Crombie, R. I. (1993). The Cuban crocodile, Crocodylus rhombifer, from late quaternary fossil deposits on Grand Cayman. Caribbean Journal of Science, 29(3–4), 153–164.
Alligators are notable for their ability to inhabit climates that are considerably more temperate than those of most other crocodilians. Although they generally prefer subtropical to tropical regions, they are also capable of surviving colder winters in the northern parts of their range.
Evolution Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million to 65 million years ago). The Chinese alligator split from the American alligator about 33 million years ago and probably descended from a lineage that crossed the Bering land bridge during the Neogene. The modern American alligator is well represented in the fossil record of the Pleistocene. The alligator's full mitochondrial genome was sequenced in the 1990s. The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.
Phylogeny The genus Alligator belongs to the subfamily Alligatorinae, which is the sister taxon to Caimaninae (the caimans). Together, these two subfamilies form the family Alligatoridae. The cladogram below shows the phylogeny of alligators.
Species
Extant Image Scientific name Common name Distribution Alligator mississippiensis American alligator the Southeastern United States Alligator sinensis Chinese alligator eastern China
Extinct
Alligator hailensis Alligator luicus Alligator mcgrewi Alligator mefferdi Alligator munensis Alligator olseni Alligator prenasalis Alligator thomsoni
Description
An average adult American alligator's weight and length is and , but they sometimes grow to long and weigh over . The largest ever recorded, found in Louisiana, measured . The Chinese alligator is smaller, rarely exceeding in length. Additionally, it weighs considerably less, with males rarely over .
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.
Habitat
Alligators are native only to the United States and China.
American alligators are found in the southeast United States: all of Florida and Louisiana; the southern parts of Georgia, Alabama, and Mississippi; coastal South 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 crocodiles coexist."Trappers catch crocodile in Lake Tarpon", Tampa Bay Times, July 12, 2013
American alligators live in freshwater environments, such as ponds, wetlands, rivers, and lakes, 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 nutrias and muskrats 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. Miami MetroZoo in Florida also has a breeding pair of Chinese alligators.
Behavior
Large male alligators are solitary territorial animals. Smaller alligators can often be found in large numbers close to each other. The largest of the species (both males and females) defend prime territory; smaller alligators have a higher tolerance for other alligators within a similar size class.
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.
Diet
The type of food eaten by alligators depends upon their age and size. When they are young, alligators eat fish, insects, snails, crustaceans, and worms. As they mature, progressively larger prey is taken, including larger fish, such as gar, turtles, and various mammals, particularly nutrias and muskrats, as well as birds, deer, and other reptiles.Wolfe, J. L., D. K. Bradshaw, and R. H. Chabreck. 1987. Alligator feeding habits: New data and a review. Northeast Gulf Science 9: 1–8.Gabrey, S. W. 2005. Impacts of the coypu removal program on the diet of American alligators (Alligator mississippiensis) in south Louisiana. Report to Louisiana Department of Wildlife and Fisheries, New Orleans. Their stomachs also often contain gizzard stones. They will consume carrion if they are sufficiently hungry. In some cases, larger alligators are known to ambush dogs, Florida panthers, and black bears, making them the apex predator throughout their distribution. In this role as a top predator, it may determine the abundance of prey species, including turtles and nutrias.Bondavalli, C., and R. E. Ulanowicz. 1998. Unexpected effects of predators upon their prey: The case of the American alligator. Ecosystems 2: 49–63.
Reproduction
Alligators generally mature at a length of . The mating season is in late spring. In April and May, alligators form so-called "bellowing choruses". Large groups of animals bellow together for a few minutes a few times a day, usually one to three hours after sunrise. The bellows of male American alligators are accompanied by powerful blasts of infrasound. Another form of male display is a loud head-slap. In 2010, on spring nights alligators were found to gather in large numbers for group courtship, the so-called "alligator dances".
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.
Anatomy