American alligator

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American alligator
Temporal range: Miocene–Recent, 8–0  Ma [1]
American Alligator.jpg
At the Columbus Zoo and Aquarium in Powell, Ohio
CITES Appendix II (CITES) [3]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Alligatoridae
Subfamily: Alligatorinae
Genus: Alligator
Species:
A. mississippiensis
Binomial name
Alligator mississippiensis
(Daudin, 1802)
The range of the American Alligator.png
Approximate range of American alligator
Synonyms [4]

The American alligator (Alligatormississippiensis), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States and a small section of northeastern Mexico. It is one of the two extant species in the genus Alligator , and is larger than the only other living alligator species, the Chinese alligator.

Contents

Adult male American alligators measure 3.4 to 4.6 m (11.2 to 15.1 ft) in length, and can weigh up to 500 kg (1,100 lb), with unverified sizes of up to 5.84 m (19.2 ft) and weights of 1,000 kg (2,200 lb) making it the second largest member of the family Alligatoridae, after the black caiman. Females are smaller, measuring 2.6 to 3 m (8.5 to 9.8 ft) in length. [5] [6] [7] [8] [9] The American alligator inhabits subtropical and tropical freshwater wetlands, such as marshes and cypress swamps, from southern Texas to North Carolina. [10] It is distinguished from the sympatric American crocodile by its broader snout, with overlapping jaws and darker coloration, and is less tolerant of saltwater but more tolerant of cooler climates than the American crocodile, which is found only in tropical and warm subtropical climates.

American alligators are apex predators and consume fish, amphibians, reptiles, birds, and mammals. Hatchlings feed mostly on invertebrates. They play an important role as ecosystem engineers in wetland ecosystems through the creation of alligator holes, which provide both wet and dry habitats for other organisms. Throughout the year (in particular during the breeding season), American alligators bellow to declare territory, and locate suitable mates. [11] Male American alligators use infrasound to attract females. Eggs are laid in a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water. Young are born with yellow bands around their bodies and are protected by their mother for up to one year. [12]

The conservation status of the American alligator is listed as Least Concern by the International Union for Conservation of Nature. Historically, hunting had decimated their population, and the American alligator was listed as an endangered species by the Endangered Species Act of 1973. Subsequent conservation efforts have allowed their numbers to increase and the species was removed from endangered status in 1987. The species is the official state reptile of three states: Florida, Louisiana, and Mississippi.

Taxonomy

In the Okefenokee Swamp AlligatorFL2007.JPG
In the Okefenokee Swamp

The American alligator was first classified by French zoologist François Marie Daudin as Crocodilus mississipiensis in 1801. In 1807, Georges Cuvier created the genus Alligator; [13] the American alligator and the Chinese alligator are the only extant species in the genus. They are grouped in the family Alligatoridae with the caimans. The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator than to either the Nile crocodile (Crocodylus niloticus) or the gharial (Gavialis gangeticus). [14]

Phylogeny

Members of this superfamily first arose in the late Cretaceous, about 100–65 million years ago (Mya). Leidyosuchus of Alberta is the earliest known fossil, from the Campanian era 83 to 72 Mya. Fossil alligatoroids have been found throughout Eurasia, because bridges across both the North Atlantic and the Bering Strait connected North America to Eurasia about 66 to 23 Mya.

Alligators and caimans split in North America during the late Cretaceous, and the caimans reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period, from about 23 to 2.58 Mya. The Chinese alligator likely descended from a lineage that crossed the Bering land bridge during the Neogene. Fossils identical to the existing American alligator are found throughout the Pleistocene, from 2.5 million to 11.7 thousand years ago. [15] In 2016, a Miocene (about 23 to 5.3 Mya) fossil skull of an alligator was found at Marion County, Florida. Unlike the other extinct alligator species of the same genus, the fossil skull was virtually indistinguishable from that of the modern American alligator. This alligator and the American alligator are now considered to be sister taxa, meaning that the A. mississippiensis lineage has existed in North America for over 8 million years. [16]

The alligator's full mitochondrial genome was sequenced in the 1990s, and it suggests the animal evolved at a rate similar to mammals and greater than birds and most cold-blooded vertebrates. [17] However, the full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds. [18]

Characteristics

American alligator skull Alligator Crane et Mandibule.jpg
American alligator skull

Domestic American alligators range from long and slender to short and robust, possibly in response to variations in factors such as growth rate, diet, and climate.

Size

The American alligator is a relatively large species of crocodilian. On average, it is the largest species in the family Alligatoridae, with only the black caiman being possibly larger. [19] Weight varies considerably depending on length, age, health, season, and available food sources. Similar to many other reptiles that range expansively into temperate zones, American alligators from the northern end of their range, such as southern Arkansas, Alabama, and northern North Carolina, tend to reach smaller sizes. Large adult American alligators tend to be relatively robust and bulky compared to other similar-length crocodilians; for example, captive males measuring 3 to 4 m (9 ft 10 in to 13 ft 1 in) were found to weigh 200 to 350 kg (440 to 770 lb), although captive specimens may outweigh wild specimens due to lack of hunting behavior and other stressors. [20] [21]

Large male American alligators reach an expected maximum size up to 4.6 m (15 ft 1 in) in length and weighing up to 500 kg (1,100 lb), while females reach an expected maximum of 3 m (9 ft 10 in). [5] [6] [22] However, the largest free-ranging female had a total length of 3.22 m (10 ft 7 in) and weighed 170 kg (370 lb). [23] On rare occasions, a large, old male may grow to an even greater length. [24] [25]

Largest

During the 19th and 20th centuries, larger males reaching 5 to 6 m (16 ft 5 in to 19 ft 8 in) were reported. [26] The largest reported individual size was a male killed in 1890 on Marsh Island, Louisiana, and reportedly measured at 5.84 m (19 ft 2 in) in length, but no voucher specimen was available, since the American alligator was left on a muddy bank after having been measured due to having been too massive to relocate. [25] If the size of this animal was correct, it would have weighed about 1,000 kg (2,200 lb). [27] In Arkansas, a man killed an American alligator that was 4.04 m (13 ft 3 in) and 626 kg (1,380 lb). [28] The largest American alligator ever killed in Florida was 5.31 m (17 ft 5 in), as reported by the Everglades National Park, although this record is unverified. [29] [30] The largest American alligator scientifically verified in Florida for the period from 1977 to 1993 was reportedly 4.23 m (13 ft 11 in) and weighed 473 kg (1,043 lb), although another specimen (size estimated from skull) may have measured 4.54 m (14 ft 11 in). [20] A specimen that was 4.5 m (14 ft 9 in) long and weighed 458.8 kg (1,011.5 lb) is the largest American alligator killed in Alabama and has been declared the SCI world record in 2014. [31] [32]

Reported sizes

Average

American alligators do not normally reach such extreme sizes. In mature males, most specimens grow up to about 3.4 m (11 ft 2 in) in length, and weigh up to 360 kg (790 lb), [7] while in females, the mature size is normally around 2.6 m (8 ft 6 in), with a body weight up to 91 kg (201 lb). [8] [9] In Newnans Lake, Florida, adult males averaged 73.2 kg (161 lb) in weight and 2.47 m (8 ft 1 in) in length, while adult females averaged 55.1 kg (121 lb) and measured 2.22 m (7 ft 3 in). [48] In Lake Griffin State Park, Florida, adults weighed on average 57.9 kg (128 lb). [49] Weight at sexual maturity per one study was stated as averaging 30 kg (66 lb) while adult weight was claimed as 160 kg (350 lb). [50]

Relation to age

There is a common belief stated throughout reptilian literature that crocodilians, including the American alligator, exhibit indeterminate growth, meaning the animal continues to grow for the duration of its life. However, these claims are largely based on assumptions and observations of juvenile and young adult crocodilians, and recent studies are beginning to contradict this claim. For example, one long-term mark-recapture study (1979–2015) done at the Tom Yawkey Wildlife Center in South Carolina found evidence to support patterns of determinate growth, with growth ceasing upon reaching a certain age (43 years for males and 31 years for females). [51]

Sexual dimorphism

While noticeable in very mature specimens, the sexual dimorphism in size of the American alligator is relatively modest among crocodilians. [52] For contrast, the sexual dimorphism of saltwater crocodiles is much more extreme, with mature males nearly twice as long as and at least four times as heavy as female saltwater crocodiles. [53] Given that female American alligators have relatively higher survival rates at an early age and a large percentage of given populations consists of immature or young breeding American alligators, relatively few large mature males of the expected mature length of 3.4 m (11 ft 2 in) or more are typically seen. [54]

Color

Dorsally, adult American alligators may be olive, brown, gray, or black. However, they are on average one of the most darkly colored modern crocodilians (although other alligatorid family members are also fairly dark), and can be reliably be distinguished by color via their more blackish dorsal scales against crocodiles. [24] Meanwhile, their undersides are cream-colored. [55] Some American alligators are missing or have an inhibited gene for melanin, which makes them albino. These American alligators are extremely rare and almost impossible to find in the wild. They could only survive in captivity, as they are very vulnerable to the sun and predators. [56]

Jaws, teeth, and snout

American alligator showing teeth AmericanAlligator3.jpg
American alligator showing teeth
The snout of an American alligator skull American alligator (Alligator mississippiensis) skull nostrils at the Royal Veterinary College anatomy museum.JPG
The snout of an American alligator skull

American alligators have 74–80 teeth. [26] As they grow and develop, the morphology of their teeth and jaws change significantly. [57] Juveniles have small, needle-like teeth that become much more robust and narrow snouts that become broader as the individuals develop. [57] These morphological changes correspond to shifts in the American alligators' diets, from smaller prey items such as fish and insects to larger prey items such as turtles, birds, and other large vertebrates. [57] American alligators have broad snouts, especially in captive individuals. When the jaws are closed, the edges of the upper jaws cover the lower teeth, which fit into the jaws' hollows. Like the spectacled caiman, this species has a bony nasal ridge, though it is less prominent. [26] American alligators are often mistaken for a similar animal: the American crocodile. An easy characteristic to distinguish the two is the fourth tooth. Whenever an American alligator's mouth is closed, the fourth tooth is no longer visible. It is enclosed in a pocket in the upper jaw.

Bite

Adult American alligators held the record as having the strongest laboratory-measured bite of any living animal, measured at up to 13,172  N (1,343.2  kgf ; 2,961  lbf ). This experiment had not been, at the time of the paper published, replicated in any other crocodilians, and the same laboratory was able to measure a greater bite force of 16,414 N (1,673.8 kgf; 3,690 lbf) in saltwater crocodiles; [58] [59] notwithstanding this very high biting force, the muscles opening the American alligator's jaw are quite weak, and the jaws can be held closed by hand or tape when an American alligator is captured. No significant difference is noted between the bite forces of male and female American alligators of equal size. [57] Another study noted that as the American alligator increases in size, the force of its bite also increases. [60]

Movement

"High walk" of an American alligator AmericanAlligator77.JPG
"High walk" of an American alligator
X-ray video of a female American alligator showing contraction of the lungs while breathing

When on land, an American alligator moves either by sprawling or walking, the latter involving the reptile lifting its belly off the ground. The sprawling of American alligators and other crocodylians is not similar to that of salamanders and lizards, being similar to walking. Therefore, the two forms of land locomotion can be termed the "low walk" and the "high walk". Unlike most other land vertebrates, American alligators increase their speed through the distal rather than proximal ends of their limbs. [61] In the water, American alligators swim like fish, moving their pelvic regions and tails from side to side. [62] During respiration, air flow is unidirectional, looping through the lungs during inhalation and exhalation; [63] the American alligator's abdominal muscles can alter the position of the lungs within the torso, thus shifting the center of buoyancy, which allows the American alligator to dive, rise, and roll within the water. [64]

Distribution

American alligator (right) and American crocodile (left) at Mrazek Pond, Florida Crocodile and Gator at Mrazek Pond (2), EVER, NPSPhoto, SCotrell, 4-2011 (9255694189).jpg
American alligator (right) and American crocodile (left) at Mrazek Pond, Florida

American alligators, being native both to the Nearctic and Neotropical realms, are found in the wild in the Southeastern United States, from the Lowcountry in South Carolina, south to Everglades National Park in Florida, and west to the southeastern region of Texas. [65] They are found in parts of North Carolina, South Carolina, Georgia, Florida, Louisiana, Alabama, Mississippi, Arkansas, Oklahoma and Texas. Some of these locations appear to be relatively recent introductions, with often small but reproductive populations. [66] Louisiana has the largest American alligator population of any U.S. state. In the future, possible American alligator populations may be found in areas of Mexico adjacent to the Texas border. [67] American alligators have been naturally expanding their range into Tennessee, [68] and have established a small population in the southwestern part of that state via inland waterways, according to the state's wildlife agency. [69] They have been extirpated from Virginia, and occasional vagrants from North Carolina wander into the Great Dismal Swamp. [70]

Conservation status

A leucistic American alligator at Gatorland LeucisticAlligator.jpg
A leucistic American alligator at Gatorland

American alligators are currently listed as least concern by the IUCN Red List, [2] even though from the 1800s to the mid-1900s, they were being hunted and poached by humans unsustainably.

Historically, hunting and habitat loss have severely affected American alligator populations throughout their range, and whether the species would survive was in doubt. In 1967, the American alligator was listed as an endangered species (under a law that was the precursor Endangered Species Act of 1973), since it was believed to be in danger of extinction throughout all or a significant portion of its range. [71]

Both the United States Fish and Wildlife Service (USFWS) and state wildlife agencies in the South contributed to the American alligator's recovery. Protection under the Endangered Species Act allowed the species to recuperate in many areas where it had been depleted. States began monitoring their American alligator populations to ensure that they would continue to grow. In 1987, the USFWS removed the animal from the endangered species list, as it was considered to be fully recovered. [72] The USFWS still regulates the legal trade in American alligators and their products to protect still endangered crocodilians that may be passed off as American alligators during trafficking. [71]

American alligators are listed under Appendix II of the Convention on International Trade in Endangered Species (CITES) meaning that international trade in the species (including parts and derivatives) is regulated. [3]

Habitat

They inhabit swamps, streams, rivers, ponds, and lakes. A lone American alligator was spotted for over 10 years living in a river north of Atlanta, Georgia. [73] Females and juveniles are also found in Carolina Bays and other seasonal wetlands. While they prefer fresh water, American alligators may sometimes wander into brackish water, [74] but are less tolerant of salt water than American crocodiles, as the salt glands on their tongues do not function. [75] One study of American alligators in north-central Florida found the males preferred open lake water during the spring, while females used both swampy and open-water areas. During summer, males still preferred open water, while females remained in the swamps to construct their nests and lay their eggs. Both sexes may den underneath banks or clumps of trees during the winter. [48]

In some areas of their range, American alligators are an unusual example of urban wildlife; golf courses are often favored by the species due to an abundance of water and a frequent supply of prey animals such as fish and birds. [76] [77]

Cold tolerance

American alligators are less vulnerable to cold than American crocodiles. Unlike an American crocodile, which would immediately succumb to the cold and drown in water at 45 °F (7 °C) or less, an American alligator can survive in such temperatures for some time without displaying any signs of discomfort. [78] This adaptiveness is thought to be why American alligators are widespread further north than the American crocodile. [78] In fact, the American alligator is found farther from the equator and is more equipped to handle cooler conditions than any other crocodilian. [79] When the water begins to freeze, American alligators go into a period of brumation; they stick their snouts through the surface, which allows them to breathe above the ice, [74] and they can remain in this state for several days. [80]

Ecology and behavior

Basking

An American alligator basks on the bank of a pond in Big Cypress National Preserve. Alligator mississippiensis (American alligator) 6.jpg
An American alligator basks on the bank of a pond in Big Cypress National Preserve.

American alligators primarily bask on shore, but also climb into and perch on tree limbs to bask if no shoreline is available. This is not often seen, since if disturbed, they quickly retreat back into the water by jumping from their perch. [81]

Holes

American alligators modify wetland habitats, most dramatically in flat areas such as the Everglades, by constructing small ponds known as alligator holes. This behavior has qualified the American alligator to be considered a keystone species. Alligator holes retain water during the dry season and provide a refuge for aquatic organisms, which survive the dry season by seeking refuge in alligator holes, so are a source of future populations. The construction of nests along the periphery of alligator holes, as well as a buildup of soils during the excavation process, provides drier areas for other reptiles to nest and a place for plants that are intolerant of inundation to colonize. Alligator holes are an oasis during the Everglades dry season, so are consequently important foraging sites for other organisms. [82] In the limestone depressions of cypress swamps, alligator holes tend to be large and deep, while those in marl prairies and rocky glades are usually small and shallow, and those in peat depressions of ridge and slough wetlands are more variable. [83]

A young American alligator preying on a bullfrog Gator with bullfrog at Lake Woodruff - Flickr - Andrea Westmoreland.jpg
A young American alligator preying on a bullfrog
American alligator in the Everglades

Prey

Bite and mastication

The teeth of the American alligator are designed to grip prey, but cannot rip or chew flesh like teeth of some other predators (such as canids and felids), and depend on their gizzard, instead, to masticate their food. The American alligator is capable of biting through a turtle's shell or a moderately sized mammal bone. [84]

Tool use

American alligators have been documented using lures to hunt prey such as birds. [85] This means they are among the first reptiles recorded to use tools. By balancing sticks and branches on their heads, American alligators are able to lure birds looking for suitable nesting material to kill and consume. This strategy, which is shared by the mugger crocodile, is particularly effective during the nesting season, in which birds are more likely to gather appropriate nesting materials. [86] This strategy has been documented in two Florida zoos occurring multiple times a day in peak nesting season and in some parks in Louisiana. The use of tools was documented primarily during the peak rookery season when birds were primarily looking for sticks. [87]

Aquatic vs terrestrial

American alligator about to eat a crab American Alligator eating Blue Crab 2.JPG
American alligator about to eat a crab

Fish and other aquatic prey taken in the water or at the water's edge form the major part of American alligator's diet and may be eaten at any time of the day or night. Adult American alligators also spend considerable time hunting on land, up to 160 feet (50 m) from water, ambushing terrestrial animals on trailsides and road shoulders. Usually, terrestrial hunting occurs on nights with warm temperatures. [88] When hunting terrestrial prey, American alligators may also ambush them from the edge of the water by grabbing them and pulling the prey into the water, the preferred method of predation of larger crocodiles. [24]

An American alligator in the process of consuming a slider turtle Alligator consuming turtle2.jpg
An American alligator in the process of consuming a slider turtle

Additionally, American alligators have recently been filmed and documented killing and eating sharks and rays; four incidents documented indicated that bonnetheads, lemon sharks, Atlantic stingrays, and nurse sharks are components of the animal's diet. Sharks are also known to prey on American alligators, in turn, indicating that encounters between the two predators are common. [89] [90]

Common

American alligators are considered an apex predator throughout their range. They are opportunists and their diet is determined largely by both their size and age and the size and availability of prey. Most American alligators eat a wide variety of animals, including invertebrates, fish, birds, turtles, snakes, amphibians, and mammals. Hatchlings mostly feed on invertebrates such as insects, insect larvae, snails, spiders, and worms, as well as small fish and frogs. [91] [92] As they grow, American alligators gradually expand to larger prey. Once an American alligator reaches full size and power in adulthood, any animal living in the water or coming to the water to drink is potential prey. Most animals captured by American alligators are considerably smaller than itself. [26] A few examples of animals consumed are largemouth bass, spotted gar, freshwater pearl mussels, American green tree frogs, yellow mud turtles, cottonmouths, common moorhens, and feral wild boars. [91] Stomach contents show, among native mammals, muskrats and raccoons are some of the most commonly eaten species. [93] In Louisiana, where introduced nutria are common, they are perhaps the most regular prey for adult American alligators, although only larger adults commonly eat this species. [94] [93] It has also been reported that large American alligators prey on medium-sized American alligators, which had preyed on hatchlings and smaller juveniles. [95]

If an American alligator's primary food resource is not available, it will sometimes feed on carrion and non-prey items such as rocks and artificial objects, like bottle caps. These items help the American alligator in the process of digestion by crushing up the meat and bones of animals, especially animals with shells. [91]

Large animals

Other animals may occasionally be eaten, even large deer or feral wild boars, but these are not normally part of the diet. American alligators occasionally prey on large mammals, but usually do so when fish and smaller prey levels go down. [96] Rarely, American alligators have been observed killing and eating bobcats, but such events are not common and have little effect on bobcat populations. [97] [98] Although American alligators have been listed as predators of the Nilgai and the West Indian manatees, very little evidence exists of such predation. [99] In the 2000s, when invasive Burmese pythons first occupied the Everglades, American alligators have been recorded preying on sizable snakes, possibly controlling populations and preventing the invasive species from spreading northwards. [100] However, the python is also known to occasionally prey on alligators, a form of both competition and predation. [101] American alligator predation on Florida panthers is rare, but has been documented. Such incidents usually involve a panther trying to cross a waterway or coming down to a swamp or river to get a drink. [102] American alligator predation on American black bears has also been recorded. [103] [104] [105]

Domestic animals

Occasionally, domestic animals, including dogs, cats, and calves, are taken as available, but are secondary to wild and feral prey. [26] Other prey, including snakes, lizards, and various invertebrates, are eaten occasionally by adults. [24]

Birds

Water birds, such as herons, egrets, storks, waterfowl and large dabbling rails such as gallinules or coots, are taken when possible. Occasionally, unwary adult birds are grabbed and eaten by American alligators, but most predation on bird species occurs with unsteady fledgling birds in late summer, as fledgling birds attempt to make their first flights near the water's edge. [24]

Fruit

In 2013, American alligators and other crocodilians were reported to also eat fruit. [106] Such behavior has been witnessed, as well as documented from stomach contents, with the American alligators eating such fruit as wild grapes, elderberries, and citrus fruits directly from the trees. Thirty-four families and 46 genera of plants were represented among seeds and fruits found in the stomach contents of alligators. [107] The discovery of this unexpected part of the American alligator diet further reveals that they may be responsible for spreading seeds from the fruit they consume across their habitat. [108]

Cooperative hunting

Additionally, American alligators engage in what seems to be cooperative hunting. [109] [110] One observation of cooperative hunting techniques was where there are pushing American alligators and catching American alligators and they were observed taking turns in each position. Another observation said that about 60 American alligators gathered in an area and would form a semicircle with about half of them and would push the fish closer to the bank. Once one of the American alligators caught a fish another one would enter into its spot, and it would take the fish to the resting area. This was reported to have occurred two days in a row. [111]

In Florida and East Texas

The diet of adult American alligators from central Florida lakes is dominated by fish, but the species is highly opportunistically based upon local availability. In Lake Griffin, fish made up 54% of the diet by weight, with catfish being most commonly consumed, while in Lake Apopka, fish made up 90% of the food and mostly shad were taken; in Lake Woodruff, the diet was 84% fish and largely consists of bass and sunfish. Unusually in these regions, reptiles and amphibians were the most important nonpiscivore prey, mostly turtles and water snakes. [112] In southern Louisiana, crustaceans (largely crawfish and crabs) were found to be present in the southeastern American alligators, but largely absent in southwestern American alligators, which consumed a relatively high proportion of reptiles, although fish were the most recorded prey for adults, and adult males consumed a large portion of mammals. [113]

In East Texas, diets were diverse and adult American alligators took mammals, reptiles, amphibians, and invertebrates (e.g. snails) in often equal measure as they did fish. [114]

Vocalizations

Mechanism

An American alligator is able to abduct and adduct the vocal folds of its larynx, but not to elongate or shorten them; yet in spite of this, it can modulate fundamental frequency very well. [115] Their vocal folds consists of epithelium, lamina propria and muscle. Sounds ranged from 50 to 1200 Hz. In one experiment conducted on the larynx, the fundamental frequency depended on both the glottal gap and stiffness of the larynx tissues. As the frequency increases, there's high tension and large strains. The fundamental frequency has been influenced by the glottal gap size and subglottal pressure and when the phonation threshold pressure has been exceeded, there will be vocal fold vibration. [116]

Calls

Crocodilians are the most vocal of all non-avian reptiles and have a variety of different calls depending on the age, size, and sex of the animal. [117] The American alligator can perform specific vocalizations to declare territory, signal distress, threaten competitors, and locate suitable mates. Juveniles can perform a high-pitched hatchling call (a "yelping" trait common to many crocodilian species' hatchling young) [118] to alert their mothers when they are ready to emerge from the nest. Juveniles also make a distress call to alert their mothers if they are being threatened. Adult American alligators can growl, hiss, or cough to threaten others and declare territory.

Bellowing

Both males and females bellow loudly by sucking air into their lungs and blowing it out in intermittent, deep-toned roars to attract mates and declare territory. [119] Males are known to use infrasound during mating bellows. Bellowing is performed in a "head oblique, tail arched" posture. Infrasonic waves from a bellowing male can cause the surface of the water directly over and to either side of his back to literally "sprinkle", [120] in what is commonly called the "water dance". [121] Large bellowing "choruses" of American alligators during the breeding season are commonly initiated by females and perpetuated by males. [122] Observers of large bellowing choruses have noted they are often felt more than they are heard due to the intense infrasound emitted by males. American alligators bellow in B flat (specifically "B♭1", defined as an audio frequency of 58.27 Hz), and bellowing choruses can be induced by tuba players, sonic booms, and large aircraft. [123]

Lifespan

American alligators typically live to the age of 50, and possibly over 70 years old. Males reach sexual maturity at around 11.6 years, and females at around 15.8 years. Although it was originally thought that American alligators never stop growing, studies have now found that males stop growing at around the age of 43 years, and females stop growing at around the age of 31 years. [51]

Reproduction

Nest and young in Florida Crocnest.JPG
Nest and young in Florida
Young American alligator swimming, showing the distinctive yellow striping found on juveniles Alligator mississippiensis baby.jpg
Young American alligator swimming, showing the distinctive yellow striping found on juveniles
Juvenile resting on adult Alligator mississippiensis 113744549.jpg
Juvenile resting on adult

Breeding season

The breeding season begins in the spring. On spring nights, American alligators gather in large numbers for group courtship, in the aforementioned "water dances". [124] The female builds a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water.

Eggs

After the female lays her 20 to 50 white eggs, about the size of a goose egg, she covers them with more vegetation, which heats as it decays, helping to keep the eggs warm. This differs from Nile crocodiles, which lay their eggs in pits. [78] The temperature at which American alligator eggs develop determines their sex (see temperature-dependent sex determination). Studies have found that eggs hatched at a temperature below 88.7 °F or a temperature above 94.1 °F will produce female offspring, while those at a temperature between 90.5 °F to 92.3 °F will produce male offspring. [125] The nests built on levees are warmer, thus produce males, while the cooler nests of wet marsh produce females. [126] The female remains near the nest throughout the 65-day incubation period, protecting it from intruders. When the young begin to hatch — their "yelping" calls can sometimes even be heard just before hatching commences — the mother quickly digs them out and carries them to the water in her mouth, [26] as some other crocodilian species are known to do.

Young

The young are tiny replicas of adults, with a series of yellow bands around their bodies that serve as camouflage. [26] Hatchlings gather into pods and are guarded by their mother and keep in contact with her through their "yelping" vocalizations. Young American alligators eat small fish, frogs, crayfish, and insects. [127] They are preyed on by large fish, birds, raccoons, Florida panthers, and adult American alligators. [26] Mother American alligators eventually become more aggressive towards their young, which encourages them to disperse. [127] Young American alligators grow 3–8 in (7.6–20.3 cm) a year and reach adulthood at 6 ft (1.8 m). [74]

Parasites

American alligators are commonly infected with parasites. In a 2016 Texas study, 100% of the specimens collected were infected with parasites, and by at least 20 different species of parasites, including lung pentastomids, gastric nematodes, intestinal helminths. When compared to American alligators from different states there was no significant difference in prevalence. [128]

Interactions with exotic species

Nutria were introduced into coastal marshes from South America in the mid-20th century, and their population has since exploded into the millions. They cause serious damage to coastal marshes and may dig burrows in levees. Hence, Louisiana has had a bounty to try to reduce nutria numbers. Large American alligators feed heavily on nutria, so American alligators may not only control nutria populations in Louisiana, but also prevent them spreading east into the Everglades. Since hunting and trapping preferentially take the large American alligators that are the most important in eating nutria, some changes in harvesting may be needed to capitalize on their ability to control nutria. [94]

Recently, a population of Burmese pythons became established in Everglades National Park. Substantial American alligator populations in the Everglades might be a contributing factor, as a competitor, in keeping the python populations low, preventing the spread of the species north. While events of predation by Burmese pythons on any sizable American alligators have been observed, [101] [129] [130] no evidence of a net negative effect has been seen on overall American alligator populations. [131]

Indicators of environmental restoration

American alligator at Avery Island, Louisiana Avery Island, Louisiana-044.JPG
American alligator at Avery Island, Louisiana

American alligators play an important role in the restoration of the Everglades as biological indicators of restoration success. [132] American alligators are highly sensitive to changes in the hydrology, salinity, and productivity of their ecosystems; all are factors that are expected to change with Everglades restoration. American alligators also may control the long-term vegetation dynamics in wetlands by reducing the population of small mammals, particularly nutria, which may otherwise overgraze marsh vegetation. [94] In this way, the vital ecological service they provide may be important in reducing rates of coastal wetland losses in Louisiana. [133] They may provide a protection service for water birds nesting on islands in freshwater wetlands. American alligators prevent predatory mammals from reaching island-based rookeries and in return eat spilled food and birds that fall from their nests. Wading birds appear to be attracted to areas with American alligators and have been known to nest at heavily trafficked tourist attractions with large numbers of American alligators, such as the St. Augustine Alligator Farm in St. Augustine, Florida. [134]

Relationship with humans

An American alligator swimming in an enclosure at a zoo. American alligator swimming.jpg
An American alligator swimming in an enclosure at a zoo.

Attacks on humans

Defensive American alligator with mouth open Alligator mississippiensis defensive.jpg
Defensive American alligator with mouth open

American alligators are capable of killing humans, but fatal attacks are rare. Mistaken identity leading to an attack is always possible, especially in or near cloudy waters. American alligators are often less aggressive towards humans than larger crocodile species, a few of which (mainly the Nile and saltwater crocodiles) may prey on humans with some regularity. [25] [135] Alligator bites are serious injuries, due to the reptile's sheer bite force and risk of infection. Even with medical treatment, an American alligator bite may still result in a fatal infection. [136]

As human populations increase, and as they build houses in low-lying areas, or fish or hunt near water, incidents are inevitable where humans intrude on American alligators and their habitats. Since 1948, 257 documented attacks on humans in Florida (about five incidents per year) have been reported, of which an estimated 23 resulted in death. [137] Only nine fatal attacks occurred in the United States throughout the 1970s–1990s, but American alligators killed 12 people between 2001 and 2007. An additional report of alligator attacks showed a total of 376 injuries and 15 deaths recorded all from 1948 to 2004, leading this to an increase of the alligator population. [138] In May 2006, American alligators killed three Floridians in less than a week. [139] At least 28 fatal attacks by American alligators have occurred in the United States since 1970.

Wrestling

Man wrestling American alligator GilletteAlligatorWrestling.jpg
Man wrestling American alligator

Since the late 1880s, alligator wrestling has been a source of entertainment for some. Created by the Miccosukee and Seminole tribes prior to the arrival of Europeans, this tourism tradition remains popular despite criticism from animal-rights activists. [140]

Farming

Alligator skins FMIB 33999 Alligator Skins edited.png
Alligator skins

Today, alligator farming is a large, growing industry in Georgia, 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- to 7-ft range have sold for $300 each. [141] The market for alligator meat is growing, and about 300,000 pounds (140,000 kg) of meat are produced annually. [142] According to the Florida Department of Agriculture and Consumer Services, raw alligator meat contains roughly 200 Calories (840 kJ) per 3-oz (85-g) portion, of which 27 Calories (130 kJ) come from fat.

An American alligator sunning itself on the grass at a zoo. American alligator on grass.jpg
An American alligator sunning itself on the grass at a zoo.

Culture and film

The American alligator is the official state reptile of Florida, [143] Louisiana, [144] and Mississippi. [145] Several organizations and products from Florida have been named after the animal.

"Gators" has been the nickname of the University of Florida's sports teams since 1911. In 1908, a printer made a spur-of-the-moment decision to print an alligator emblem on a shipment of the school's football pennants. [146] The mascot stuck, and was made official in 1911, perhaps because the team captain's nickname was Gator. [147] Allegheny College and San Francisco State University both have Gators as their mascots, as well. [148]

The Gator Bowl is a college football game held in Jacksonville annually since 1946, with Gator Bowl Stadium hosting the event until the 1993 edition. The Gatornationals is a NHRA drag race held at the Gainesville Raceway in Gainesville since 1970.

See also

Related Research Articles

<span class="mw-page-title-main">Crocodile</span> Family of large reptilian carnivores

Crocodiles or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant members of the order Crocodilia, which includes the alligators and caimans, the gharial and false gharial among other extinct taxa.

<span class="mw-page-title-main">Crocodilia</span> Order of mostly large, predatory, semiaquatic reptiles

Crocodilia is an order of mostly large, predatory, semiaquatic reptiles known as crocodilians. They first appeared 94 million years ago in the Late Cretaceous period and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the order's total group, the clade Pseudosuchia, appeared about 250 million years ago in the Early Triassic period, and diversified during the Mesozoic era. The order Crocodilia includes the true crocodiles, the alligators and caimans, and the gharial and false gharial. Although the term crocodiles is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group.

<span class="mw-page-title-main">Alligator</span> Crocodilian in the genus Alligator of the family Alligatoridae

An alligator, or colloquially gator, is a large reptile in the genus Alligator of the family Alligatoridae of the order Crocodilia. The two extant species are the American alligator and the Chinese alligator. Additionally, several extinct species of alligator are known from fossil remains. Alligators first appeared during the Oligocene epoch about 37 million years ago.

<span class="mw-page-title-main">Saltwater crocodile</span> Reptile of South Asia, Southeast Asia and Oceania

The saltwater crocodile is a crocodilian native to saltwater habitats, brackish wetlands and freshwater rivers from India's east coast across Southeast Asia and the Sundaic region to northern Australia and Micronesia. It has been listed as Least Concern on the IUCN Red List since 1996. It was hunted for its skin throughout its range up to the 1970s, and is threatened by illegal killing and habitat loss. It is regarded as dangerous to humans.

<span class="mw-page-title-main">Black caiman</span> Largest extant species of caiman

The black caiman is a crocodilian reptile endemic to South America. With a maximum length of around 5 to 6 m and a mass of over 450 kg (1,000 lb), it is the largest living species of the family Alligatoridae, and the third-largest crocodilian in the Neotropical realm. True to its common and scientific names, the black caiman has a dark greenish-black coloration as an adult. In some individuals, the pigmentation can appear almost jet-black. It has grey to brown banding on the lower jaw; juveniles have a more vibrant coloration compared to adults, with prominent white-pale yellow banding on the flanks that remains present well into adulthood. The banding on young animals helps with camouflage by breaking up their body outline, on land or in water, in an effort to avoid predation. The morphology is quite different from other caimans but the bony ridge that occurs in other caimans is present. The head is large and heavy, an advantage in catching larger prey. Like all crocodilians, caimans are long, squat creatures, with big jaws, long tails and short legs. They have thick, scaled skin, and their eyes and noses are located on the tops of their heads. This enables them to see and breathe while the rest of their bodies are underwater.

<span class="mw-page-title-main">Chinese alligator</span> One of two species in genus Alligator

The Chinese alligator, also known as the Yangtze alligator, China alligator, or historically the muddy dragon, is a crocodilian endemic to China. It and the American alligator are the only living species in the genus Alligator of the family Alligatoridae. Dark gray or black in color with a fully armored body, the Chinese alligator grows to 1.5–2.1 metres (5–7 ft) in length and weighs 36–45 kilograms (80–100 lb) as an adult. It brumates in burrows in winter and is nocturnal in summer. Mating occurs in early summer, with females most commonly producing 20–30 eggs, which are smaller than those of any other crocodilian. The species is an opportunistic feeder, primarily eating fish and invertebrates. A vocal species, adults bellow during the mating season and young vocalize to communicate with their parents and other juveniles. Captive specimens have reached age 70, and wild specimens can live past 50.

<span class="mw-page-title-main">Nile crocodile</span> Reptile of Africa

The Nile crocodile is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed in sub-Saharan Africa, occurring mostly in the eastern, southern, and central regions of the continent, and lives in different types of aquatic environments such as lakes, rivers, swamps, and marshlands. Although capable of living in saline environments, this species is rarely found in saltwater, but occasionally inhabits deltas and brackish lakes. The range of this species once stretched northward throughout the Nile River, as far north as the Nile Delta. Generally, the adult male Nile crocodile is between 3.5 and 5 m in length and weighs 225 to 750 kg. However, specimens exceeding 6.1 m (20 ft) in length and 1,000 kg (2,200 lb) in weight have been recorded. It is the largest freshwater predator in Africa, and may be considered the second-largest extant reptile in the world, after the saltwater crocodile. Size is sexually dimorphic, with females usually about 30% smaller than males. The crocodile has thick, scaly, heavily armoured skin.

<span class="mw-page-title-main">American crocodile</span> Species of crocodile endemic to the Neotropics

The American crocodile is a species of crocodilian found in the Neotropics. It is the most widespread of the four extant species of crocodiles from the Americas, with populations present from South Florida and the coasts of Mexico to as far south as Peru, Ecuador, and Venezuela.

<i>Deinosuchus</i> Genus of a giant crocodylian

Deinosuchus is an extinct genus of alligatoroid crocodilian, related to modern alligators and caimans, that lived 82 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos (δεινός), "terrible", and soukhos (σοῦχος), "crocodile". The first remains were discovered in North Carolina in the 1850s; the genus was named and described in 1909. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator.

<span class="mw-page-title-main">Freshwater crocodile</span> Species of reptile

The freshwater crocodile, also known as the Australian freshwater crocodile, Johnstone's crocodile or the freshie, is a species of crocodile endemic to the northern regions of Australia. Unlike their much larger Australian relative, the saltwater crocodile, freshwater crocodiles are not known as man-eaters, although they bite in self-defence, and brief, nonfatal attacks have occurred, apparently the result of mistaken identity.

<span class="mw-page-title-main">Nile monitor</span> Species of lizard

The Nile monitor is a large member of the monitor family (Varanidae) found throughout most of Sub-Saharan Africa, particularly in drier regions, and along the Nile River and its tributaries in East Africa. Additionally, there are modern, invasive populations in North America. The population found in West African forests and savannahs is sometimes recognized as a separate species, the West African Nile monitor. While it is dwarfed by its larger relatives, such as the Komodo dragon, the Asian water monitor or the crocodile monitor, it is still one of the largest lizards in the world, reaching Australia’s perentie in size. Other common names include the African small-grain lizard, as well as iguana and various forms derived from it, such as guana, water leguaan or river leguaan.

<span class="mw-page-title-main">Orinoco crocodile</span> Species of reptile

The Orinoco crocodile is a critically endangered crocodile. Its population is very small, and they can only be found in the Orinoco river basin in Venezuela and Colombia. Extensively hunted for their skins in the 19th and 20th centuries, it is one of the most endangered species of crocodiles. It is a very large species of crocodilian; males have been reported up to 6.8 m in the past, weighing over 900 kg (2,000 lb), but such sizes do not exist today, 5.2 m being a more widely accepted maximum size. A large male today may attain 4.2 m in length and can weigh up to 450 kg (1,000 lb), while females are substantially smaller with the largest likely to weigh around 225 kg (496 lb). Sexual dimorphism is not as profound as in other crocodilian species. The coloration is light even in adults.

<span class="mw-page-title-main">Cuvier's dwarf caiman</span> Species of reptile

Cuvier's dwarf caiman is a small crocodilian in the alligator family from northern and central South America. It is found in Brazil, Bolivia, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Trinidad and Venezuela. It lives in riverine forests, flooded forests near lakes, and near fast-flowing rivers and streams. It can traverse dry land to reach temporary pools and tolerates colder water than other species of caimans. Other common names for this species include the musky caiman, the dwarf caiman, Cuvier's caiman, and the smooth-fronted caiman. It is sometimes kept in captivity as a pet and may be referred to as the wedge-head caiman by the pet trade community.

<span class="mw-page-title-main">Smooth-fronted caiman</span> Species of reptile

The smooth-fronted caiman, also known as Schneider's dwarf caiman or Schneider's smooth-fronted caiman, is a crocodilian from South America, where it is native to the Amazon and Orinoco Basins. It is the second-smallest species of the family Alligatoridae, the smallest being Cuvier's dwarf caiman, also from tropical South America and in the same genus. An adult typically grows to around 1.2 to 1.6 m in length and weighs between 9 and 20 kg. Exceptionally large males can reach as much as 2.3 m (7.5 ft) in length and 36 kg (79 lb) in weight.

<span class="mw-page-title-main">New Guinea crocodile</span> Species of reptile

The New Guinea crocodile is a small species of crocodile found on the island of New Guinea north of the mountain ridge that runs along the centre of the island. The population found south of the mountain ridge, formerly considered a genetically distinct population, is now considered a distinct species, Hall's New Guinea crocodile. In the past it included the Philippine crocodile, C. n. mindorensis, as a subspecies, but today they are regarded as separate species. The habitat of the New Guinea crocodile is mostly freshwater swamps and lakes. It is most active at night when it feeds on fish and a range of other small animals. A female crocodile lays a clutch of eggs in a nest composed of vegetation and she lies up nearby to guard the nest. There is some degree of parental care for newly hatched juveniles. This crocodile was over-hunted for its valuable skin in the mid 20th century, but conservation measures have since been put in place, it is reared in ranches and the International Union for Conservation of Nature (IUCN) lists it as being of "Least Concern".

<span class="mw-page-title-main">Morelet's crocodile</span> Species of reptile

Morelet's crocodile, also known as the Mexican crocodile or Belize crocodile, is a modest-sized crocodilian found only in fresh waters of the Atlantic regions of Mexico, Belize and Guatemala. It usually grows to about 3 metres (10 ft) in length. It is a Least Concern species. The species has a fossil record in Guatemala.

<span class="mw-page-title-main">Spectacled caiman</span> Species of crocodilian native to the Neotropics

The spectacled caiman, also known as the white caiman, common caiman, and speckled caiman, is a crocodilian in the family Alligatoridae. It is brownish-, greenish-, or yellowish-gray colored and has a spectacle-like ridge between its eyes, which is where its common name come from. It grows to a length of 1.4–2.5 m and a weight of 7–40 kg (15–88 lb), with males being both longer and heavier than females. Its diet varies seasonally, commonly consisting of crabs, fish, small mammals, amphibians and snails. Breeding occurs from May to August and 14–40 eggs are laid in July and August. This crocodilian has a large range and population; it is native to much of Latin America, and has been introduced to the United States, Cuba, and Puerto Rico.

<span class="mw-page-title-main">Caiman</span> Subfamily of reptiles

A caiman is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico and Central and South America from marshes and swamps to mangrove rivers and lakes. They have scaly skin and live a fairly nocturnal existence. They are relatively small-sized crocodilians with an average maximum weight of 6 to 40 kg depending on species, with the exception of the black caiman, which can grow more than 4 m (13 ft) in length and weigh in excess of 1,000 kg. The black caiman is the largest caiman species in the world and is found in the slow-moving rivers and lakes that surround the Amazon basin. The smallest species is the Cuvier's dwarf caiman, which grows to 1.2 to 1.5 m long. There are six different species of caiman found throughout the watery jungle habitats of Central and Southern America. The average length for most of the other caiman species is about 2 to 2.5 m long.

<span class="mw-page-title-main">Crocodile farm</span> Establishment for breeding and raising of crocodilians

A crocodile farm or alligator farm is an establishment for breeding and raising of crocodilians in order to produce crocodile and alligator meat, leather from crocodile and alligator skin, and other goods. Many species of both alligators and crocodiles are farmed internationally. In Louisiana alone, alligator farming is a $60 to $70 million industry. Most crocodile farms are located in Thailand.

<span class="mw-page-title-main">Dietary biology of the Nile crocodile</span>

Nile crocodiles are apex predators throughout their range. In the water, this species is an agile and rapid hunter relying on both movement and pressure sensors to catch any prey that presents itself inside or near the waterfront. Out of the water, however, the Nile crocodile can only rely on its limbs, as it gallops on solid ground, to chase prey. No matter where they attack prey, this and other crocodilians take practically all of their food by ambush, needing to grab their prey in a matter of seconds to succeed. They have an ectothermic metabolism, so can survive for long periods between meals—though when they do eat, they can eat up to half their body weight at a time. However, for such large animals, their stomachs are relatively small, not much larger than a basketball in an average-sized adult, so as a rule, they are anything but voracious eaters.

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