Alligator

Alligators
An American Alligator in captivity at the Columbus Zoo
Scientific classification
Phylum: Chordata Class: Sauropsida Order: Crocodilia Family: Alligatoridae Genus: Alligator Daudin, 1809
Species
Alligator mississippiensis Alligator sinensis

An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. The name alligator is an anglicized form of the Spanish el lagarto ("the lizard"), the name by which early Spanish explorers and settlers in Florida called the alligator. There are two living alligator species: the American Alligator (Alligator mississippiensis) and the Chinese Alligator (Alligator sinensis).

Alligatoridae

Alligators and caimans are reptiles, small species of crocodilians and forming the family Alligatoridae (sometimes regarded instead as the subfamily Alligatorinae).

Alligators differ from crocodiles principally in having wider and shorter heads, with more obtuse snouts; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in lacking a jagged fringe which appears on the hind legs and feet of the crocodile; in having the toes of the hind feet webbed not more than half way to the tips; and in tolerance to salinity, alligators strongly preferring fresh water, while crocodiles can tolerate salt water due to specialized glands for filtering out salt. In general, crocodiles tend to be more dangerous to humans than alligators.

Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age.

The true alligators are now restricted to two species, A. mississippiensis in the Southern United States, which grows to an average of 4 m (12 ft), with the record of 5.79 m (19 ft) in length, and the small A. sinensis in the Yangtze River, People's Republic of China, which grows to an average of 1.5 m (5 ft). Their name derives from the Spanish el lagarto, which appears to be a cognate of la lagartija, "the lizard").

In Central and South America, alligators are represented by five species of the genus Caiman, which differs from the alligator by the absence of a bony septum between the nostrils, and the ventral armour is composed of overlapping bony scutes, each of which is formed of two parts united by a suture. Some authorities further divide this genus into three, splitting off the smooth-fronted caimans into a genus Paleosuchus and the Black Caiman into Melanosuchus.

C. crocodilus, the Spectacled Caiman, has the widest distribution, from southern Mexico to the northern half of Argentina, and grows to a modest size of about 2.2 meters. The largest, attaining an enormous bulk and a length of 6 meters, is the near-threatened Melanosuchus niger, the Jacare-assu, Large, or Black Caiman of the Amazon. The Black Caiman and American Alligator are the only members of the alligator family posing the same danger to humans as the larger species of the crocodile family.

Although the Caiman has not been studied in-depth, it has been discovered that their mating cycles (previously thought to be spontaneous or year-round) are linked to the rainfall cycles and the river levels in order to increase their offspring's chances of survival.

An alligator nest at Everglades National Park, Florida.

Description

Alligators are characterized by a wider snout and eyes more dorsally located than their crocodile cousins. Both living species also tend to be darker in color, often nearly black but color is very dependent on the water. Algae-laden waters produce greener alligators; alligators from waters with a lot of tannic acid from overhanging trees are often darker (although the Chinese alligator has some light patterning.) Also, in alligators only the upper teeth can be seen with the jaws closed (in contrast to true crocodiles, in which upper and lower teeth can be seen), though many individuals bear jaw deformities which complicate this means of identification. The eyes of a large alligator will glow red and those of a smaller one will glow green when a light is shined on them. This fact can be used to find alligators in the dark.

An average American alligator's weight and length is 800 lbs. and 13 feet long. According to the Everglades National Park website, the largest alligator ever recorded in Florida was 17 feet 5 inches long (5.3 meters). The largest alligator ever recorded measured 19 feet 2 inches (5.8 meters) and was found on Marsh Island, Louisiana. Few of the giant specimens were weighed, but the larger ones could have exceeded a ton in weight. The Chinese Alligator is smaller, rarely exceeding 7 feet (2 meters) in length.

An alligator's lifespan is usually estimated in the range of 50 years or more. A specimen named Muja has resided in the Belgrade Zoo in Serbia since 1937, making it at least 70 years old. And in Riga Zoo, Latvia an alligator has been living since 1935.

Habitat

American Alligator

There are only two countries on Earth that have alligators: the United States and China.

The American Alligators normally live along the coast of the Gulf of Mexico, Texas, Oklahoma, Louisiana, Mississippi, Alabama, and Florida as well as Arkansas, Georgia and the Carolinas. However in the last few years, the alligators range appears to be increasing northward. Alligators have been seen as far north as Memphis, Tennessee, [1] , presumably arriving there by swimming up the Mississippi River. [2] The majority of American Alligators inhabit Florida and Louisiana. In Florida alone there are estimated to be more than one million alligators. The United States is the only nation on earth where both alligators and crocodiles live side by side. American Alligators live in freshwater environments, such as ponds, marshes, wetlands, rivers, and swamps, as well as brackish environments.

The Chinese alligator is endangered and lives only in the Yangtze River valley though currently Rockefeller Wildlife refuge in southern Louisiana has several in captivity in an attempt to preserve the species. There are only estimated to be a couple of dozen left in the wild. There are many more of these alligators in zoos around the world than in the wild.

Behavior

File:American Alligator in Florida.jpg

Large male alligators are solitary, territorial animals. Smaller alligators can often be found in large numbers in close proximity 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 heavy bodies and slow metabolisms, they are capable of short bursts of speed that can exceed 30 miles per hour, though this could more properly be classified as a short fast lunge rather than a dash. 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 in the water to drown. Alligators consume food that cannot be eaten in one bite by allowing it to rot or by biting and then spinning or convulsing wildly until bite-size pieces are torn off. This is referred to as the "death roll."

Most of the muscle in an alligator's jaw is intended for biting and gripping prey. The muscles that close the jaws are so strong they have the same downward force of a truck falling off a cliff. However the muscles for opening their jaws are relatively weak. As a result, an adult man can hold an alligator's jaw shut with his bare hands. In general, a simple rubber band is enough to prevent an adult alligator from opening its jaws.

Alligators are generally timid towards humans and tend to walk or swim away if one approaches. Unfortunately, this has led to humans growing arrogant and approaching alligators and their nests in a way that provokes them. There are laws against feeding the alligators but some people continue to feed them nevertheless, resulting in some of the alligators losing their fear of humans and in turn, choosing to approach humans instead of moving away.

Diet

Alligators are opportunistic feeders, eating almost anything they can catch. When they are young they eat fish, insects, snails, and crustaceans. As they grow, they take progressively larger prey items, including larger fish such as gar, turtles, various mammals, birds, and other reptiles. Their stomachs also often contain gastroliths. They will even consume carrion if they are sufficiently hungry. Adult alligators can take razorbacks and deer and are well known to kill and eat smaller alligators. In some cases, larger alligators have been known to hunt the Florida panther and bears, making it the apex predator throughout its distribution. As humans encroach onto their habitat, attacks on humans are few but not unknown. Alligators, unlike the large crocodiles, do not immediately regard a human upon encounter as prey.

Human deaths caused by alligators have increased. While there were only nine fatal attacks in the U.S.A. between 1970 and 2000, eleven people were killed by alligators in the five years between 2001 and 2006 alone. Alligators do tend to be wary of humans, but overconfidence has led some people to enter the animals' habitat in ways that provoke aggression.

Reproduction

Alligator eggs and young

Alligators of various ages in Everglades National Park

The maturity of the alligator is dependent more upon the size of the animal than its age. An alligator is generally considered mature when it reaches a length of six feet or more. They are seasonal breeders. The mating season is in spring when the water warms. The female builds a nest of vegetation that rots, incubating the eggs. Sex is fully determined at the time of hatching and irreversible thereafter, and depends on the temperature of egg incubation, temperatures of 30 °C producing females, of 34 °C yielding only males. The temperature-sensitive period is between seven and 21 days of incubation. Natural nests constructed on levees are hotter (34 °C) than those constructed on wet marsh (30 °C); 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 30 °C weigh significantly more than males hatched from eggs incubated at 34 °C.[3] The mother will defend the nest from predators and will assist the babies to water once they hatch. She will provide protection to the young for about a year if they remain in the area. The largest threat to young alligators are adults, accounting for nearly a fifty percent percent mortality rate in some cases. Incidently, in the past there have been population explosions of alligators in the years following the outlawing of alligator hunting, as the young gators have a greater chance of surviving to adulthood once much of the previous adult generation had been killed off.

Farming

Alligator farming is a big and growing industry in Florida, Texas and Louisiana. These states produce a combined annual total of some 45,000 alligator hides. Alligator hides bring good prices and hides in the 6-7 foot range have sold for $300 each, though the price can fluctuate considerably from year to year. The market for alligator meat is growing and approximately 300,000 pounds of meat is produced annually. According to the Florida Department of Agriculture, raw alligator meat contains roughly 200 calories per 3oz serving size, of which 27 calories come from fat.

The Difference Between Alligators and Crocodiles

While alligators are often confused with crocodiles, they belong to two quite separate taxonomic families, and are as distinct from one another as humans are from gorillas. As for appearance, one generally reliable rule is that alligators have U-shaped heads, while crocodiles are V-shaped - which can be remembered by noting that "A" in alligator comes before "C" in crocodile, and "U" comes before "V". Crocodiles have a longer narrower snout, with eyes further forward. Also, if one looks at an alligator and then a crocodile, one will notice a difference in their mouths: only the upper teeth are visible when an alligator's mouth is closed, while a crocodile's mouth will reveal both upper and lower teeth, as their fourth tooth sticks out from th lower jaw, rather than fitting neatly into the upper jaw. Crocodiles also tend to have green eyes, while alligators have brown ones.^{[citation needed]}

Media

Alligator bellow (file info) Alligator bellow, ogg/Vorbis format). Another alligator bellow (file info) Alligator bellow, ogg/Vorbis format). Alligator hiss (file info) Alligator hiss ogg/Vorbis format). Problems listening to the files? See media help.

Species

• ORDER Crocodilia
  • Family Alligatoridae
    • Genus Leidyosuchus (extinct)
    • Genus Deinosuchus (extinct)
    • Subfamily Alligatorinae
      • Genus Albertochampsa (extinct)
      • Genus Chrysochampsa (extinct)
      • Genus Hassiacosuchus (extinct)
      • Genus Navahosuchus (extinct)
      • Genus Ceratosuchus (extinct)
      • Genus Allognathosuchus (extinct)
      • Genus Hispanochampsa (extinct)
      • Genus Arambourgia (extinct)
      • Genus Procaimanoidea (extinct)
      • Genus Wannaganosuchus (extinct)
      • Genus Alligator
        • Alligator prenasalis (extinct)
        • Alligator mcgrewi (extinct)
        • Alligator olseni (extinct)
        • Chinese Alligator, Alligator sinensis
        • Alligator mefferdi (extinct)
        • American Alligator, Alligator mississippiensis
    • Subfamily Caimaninae
      • Genus Necrosuchus (extinct)
      • Genus Eocaiman (extinct)
      • Genus Paleosuchus
        • Cuvier's Dwarf Caiman, Paleosuchus palpebrosus
        • Smooth-fronted Caiman, Paleosuchus trigonatus
      • Genus Purussaurus (extinct)
      • Genus Mourasuchus (extinct)
      • Genus Orthogenysuchus (extinct)
      • Genus Caiman
        • Yacare Caiman, Caiman yacare
        • Spectacled Caiman, Caiman crocodilus
          • Rio Apaporis Caiman, C. c. apaporiensis
          • Brown Caiman, C. c. fuscus
        • Caiman lutescans (extinct)
        • Caiman sorontans (extinct) - Not reported in the literature, probably a nomen nudum
        • Broad-snouted Caiman, Caiman latirostris
      • Genus Melanosuchus
        • Melanosuchus fisheri (extinct)
        • Black Caiman, Melanosuchus niger

External links

Wikimedia Commons has media related to:

Alligator

• Crocodilian Online
• Everglades National Park Alligators
• Temperature of egg incubation determines sex

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