From Wikipedia, the free encyclopedia
For differences between alligators and crocodiles, see Crocodilia#Differences between alligators and crocodiles.
| Alligators Temporal range: Oligocene-Recent, 37–0Ma |
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| An American (top) and Chinese alligator (bottom) | |
Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Sauropsida |
| Clade: | Crocodylomorpha |
| Order: | Crocodylia |
| Family: | Alligatoridae |
| Subfamily: | Alligatorinae |
| Genus: | Alligator Daudin, 1809 |
| Type species | |
| Alligator mississipiensis Daudin, 1802 (originally Crocodylus) |
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| Species | |
The name alligator is an anglicized form of el lagarto, the Spanish term for "the lizard", which early Spanish explorers and settlers in Florida called the alligator.
Contents
Species (Extant)
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American alligator (Alligator mississippiensis)
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Chinese alligator (Alligator sinensis)
Description
A large adult American alligator's weight and length is 360 kg (790 lb) and 4.0 m (13.1 ft) long[citation needed], but can grow to 4.4 m (14 ft) long and weigh over 450 kg (990 lb).[2] The largest ever recorded was found in Louisiana and measured 5.84 m (19.2 ft).[3] The Chinese alligator is smaller, rarely exceeding 2.1 m (6.9 ft) in length.There is no measured average lifespan for an alligator.[4] In 1937, a one year-old specimen was brought to the Belgrade Zoo in Serbia from Germany. It is now 76 years old.[5] Although there are no valid records about its date of birth, this alligator in the Belgrade Zoo is officially named Muja (eng. Mooya), and he is considered the oldest alligator living in captivity. [6]
Habitat
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, Eastern Texas, the southeast corner of Oklahoma and the southern tip of Arkansas. According to the 2005 Scholastic Book of World Records, Louisiana is the state with the largest alligator population.[7] 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 live side by side.[citation needed]
American alligators live in freshwater environments, such as ponds, marshes, wetlands, rivers, lakes, and swamps, as well as in brackish environments.[8] When they construct gator holes in the wetlands, they increase plant diversity and also provide habitat for other animals during drought periods.[9] They are therefore considered an important species for maintaining ecological diversity in wetlands.[10] Further west, in Louisiana, heavy grazing by nutria and muskrat are causing severe damage to coastal wetlands. Large alligators feed extensively on nutria, and provide a vital ecological service by reducing nutria numbers.[11]
The Chinese alligator currently is found only in the Yangtze River valley[citation needed] and is extremely endangered, with only a few dozen believed to be left in the wild. Indeed, 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), will defend prime territory; smaller alligators have a higher tolerance of other alligators within a similar size class.Although alligators have a heavy body and a slow metabolism, they are capable of short bursts of speed, especially in very short lunges. Alligators' main prey are smaller animals that they can kill and eat with a single bite. Alligators may kill larger prey by grabbing it and dragging it into the water to drown. Alligators consume food that can not be eaten in one bite by allowing it to rot, or by biting and then spinning or convulsing wildly until bite-size chunks are torn off. This is referred to as a "death roll." 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.[12]
Most of the muscle in an alligator's jaw evolved to bite and grip prey. The muscles that close the jaws are exceptionally powerful, but the muscles for opening their jaws are comparatively weak. As a result, an adult human can hold an alligator's jaws shut barehanded. It is common today to use several wraps of duct tape to prevent an adult alligator from opening its jaws when handled or transported.[13]
Alligators are generally timid towards humans and tend to walk or swim away if one approaches. This has led some people to the practice of approaching alligators and their nests in a manner that may provoke the animals into attacking. In the state of Florida, it is illegal to feed wild alligators at any time. If fed, the alligators will eventually lose their fear of humans and will learn to associate humans with food, thereby becoming a greater danger to people.[14]
Diet
The type of food eaten by alligators depends upon their age and size. When young, alligators eat fish, insects, snails, crustaceans, and worms. As they mature, progressively larger prey is taken, including larger fish such as gar, turtles, various mammals, particularly nutria and muskrat,[8] as well as birds, deer and other reptiles.[15][16] Their stomachs also often contain gizzard stones. They will even consume carrion if they are sufficiently hungry. In some cases, larger alligators are known to ambush dogs, Florida panther and black bears, making it the apex predator throughout its distribution. In this role as a top predator, it may determine the abundance of prey species including turtles and nutria[17][18] As humans encroach onto their habitat, attacks are few but not unknown. Alligators, unlike the large crocodiles, do not immediately regard a human upon encounter as prey, but may still attack in self-defense if provoked.Reproduction
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 7 to 21 days of the start of incubation. Incubation temperatures of 86 °F (30 °C) or lower produce a clutch of females; those of 93 °F (34 °C) or higher produce entirely males. Nests constructed on leaves are hotter than those constructed on wet marsh and, thus, the former tend to produce males and the latter, females. The natural sex ratio at hatching is five females to one male. Females hatched from eggs incubated at 86 °F (30 °C) weigh significantly more than males hatched from eggs incubated at 93 °F (34 °C).[22] The mother will defend the nest from predators and will assist the hatchlings to water. She will provide protection to the young for about a year if they remain in the area. The largest threat to the young are adult alligators. Baby alligators have an egg tooth that helps them get out of their egg during hatching time. Predation by adults on young can account for a mortality rate of up to fifty percent in the first year. 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.
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Anatomy
Alligators, much like birds, have been shown to exhibit unidirectional movement of air through their lungs.[23] All other amniotes are believed to exhibit bidirectional, or tidal breathing. For a tidal breathing animal, such as a mammal, air flows into and out of the lungs through branching bronchi which terminate in small dead-end chambers called alveoli. As the alveoli represent dead-ends to flow, the inspired air must move back out the same way that it came in. In contrast air in alligator lungs makes a circuit moving in only one direction through the parabronchi. The air first enters the outer branch, moves through the parabronchi, and exits the lung through the inner branch. Extensive vasculature around the parabronchi are where oxygen exchange takes place.[24]They have a muscular flat tail that propels them while swimming.
There are two kinds of white alligators, albino and leucistic. These alligators are practically impossible to find in the wild. They could survive only in captivity and are few in number.[25][26] The Aquarium of the Americas in New Orleans has leucistic alligators found in a Louisiana swamp in 1987.[26]
Human uses
Main article: Alligator farm
Alligators are raised commercially for their meat and skin, which is
used for bags and shoes. They also provide economic benefits to humans
through the ecotourism industry, since many visitors enjoy swamp tours, in which alligators are highly valued. Their most important economic benefit to humans may be the control of nutria and muskrats.[27]
Louisiana spends millions of dollars of bounty money to control nutria;
this service is provided free by alligators. The protection of coastal
wetlands has many other economic benefits to Louisiana.
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