An
alligator is a
crocodilian in the
genus Alligator of the family
Alligatoridae. There are two
living alligator
species: the
American alligator (
Alligator mississippiensis) and the
Chinese alligator (
Alligator sinensis). In addition, several extinct species of alligator are known from fossil remains. Alligators first appeared during the
Oligocene epoch about 37 million years ago.
[1]
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.
Species (Extant)
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
Head of
Alligator mississippiensis
Eye of
Alligator mississippiensis
Alligators are native only to the United States and China.
[citation needed]
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
A rare
albino American alligator.
An albino alligator swimming.
Alligators generally mature at a length of 6 feet (1.8 m). 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-three hours after sunrise. The
bellows of male American alligators are accompanied by powerful blasts
of
infrasound.
[19] Another form of male display is a loud head-slap.
[20]
Recently it was discovered that on spring nights alligators gather in
large numbers for group courtship, the so-called "alligator dances".
[21]
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.
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.
See also
