American Alligator at Circle B Bar Reserve in Florida.

Meet the Amazing Alligator



Introduction  Taxonomy, Phylogeny & Etymology  Distribution & Population  Ecology

Anatomy & Physiology  |  Diet & Digestion  |  Thermoregulation  Reproduction  |  Neonate Care  |  Ethology

Survival  |  Human Conflict  Cultural & Commercial Impact  |  Conservation


Prime Observation Locations Bibliography  |  Filmography  |  Suggested Publications  |  References



An alli gator afloat in water reflecting the gold of a sunset.AMERICAN ALLIGATOR

Alligator mississippiensis


Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Superorder: Crocodylomorpha

Order: Crocodilia

Family: Alligatoridae

Genus: Alligator


(Image: © istockphoto/LarryLynch)



4. Anatomy & Physiology


A study of the alligator's bodily features and functions provides insight into this animal's evolution and its ability to survive to the present day. This section aims to briefly review various aspects of the anatomy and physiology. Some experts have believed that, unlike some other animals (and humans) alligators continue to grow until death, but a 2016 study indicates that this may not be the case.


SIZE. We begin with this aspect of the alligator since it is perhaps the most widely discussed feature of them all. The alligator when hatched may be as small as 8in./ 20.3cm in length. In the wild its average growth rate is about one foot per year for the first five years or so. In captivity, methods of growth inducement (particularly for hide producers) are so refined that an alligator may grow 4 ft/ 1.2m or more in the first year.


A baby alligator emerging form an egg. 

The male grows larger than the female, a condition referred to as sexual dimorphism. A female seldom grows larger than 8ft/ 2.4m while males reach 10-12ft/ 3m-3.6m and sometimes nearly as long as 14ft/ 4.3m and weighing up to 1000lbs/ 454kg. Crocodilians have one of the largest hatchling-to-adult growth ratios in the animal kingodm.


The hatchling shown at right has just emerged from the egg.

(Image: © istockphoto/clark42)



Impressive claims made regarding record sizes for alligators are many and usually sensational, resulting in widespread public misunderstanding of the maximum length of the species, and thus misperception of its danger to humans. While there are a few crocodiles found in the tropics which may measure close to 20ft / 6.1m in length, there is no evidence whatsoever that the American alligator species contemporarily reaches such size. So, the subject requires due attention here. Here are a few notes of record sizes, from which you may draw perspective.


In August, 2014 Mandy Stokes of Alabama hunted what is now considered the largest confirmed size of an alligator. The riverine bull was measured by state biologists (using scientific standards) to be 14ft. 9-1/4in/ 4.5m in length and weighing 1,011.5lbs/ 459kg (with a head length of 24in/ 61cm). The longest alligator ever found in Florida was a bull shot in the Lake Washington area of St. Johns River in Brevard County during the statewide annual harvest in 2010. One of the heaviest alligators ever  recorded was a specimen from Orange Lake in Alachua County, Florida, which weighed 1,043lbs/473kg.


E. L. McIlhenny, conservationist.Some of the largest measurements ever reported were by noted Louisiana naturalist E. L. McIlhenny of a 19ft/ 2in / 5.8m long animal and another longer than 17ft/ 5.2m. Unfortunately, there is no photographic or eyewitness confirmation for these records and there is reasonable suspicion of the claim.


E. L. McIlhenny, ca. 1930.  (Image: Public domain.)


Another among the largest, and perhaps the largest ever kept in the care of humans, was "Big George", who was caught in the wild by famed herpetologist Ross Allen. Allen claimed that the alligator measured at 14ft- 7in/ 4.4m in length (just 2.25in shy of the confirmed record), George was a major attraction for visitors to Allen's Reptile Institute at Silver Springs park in Florida. After George died, his mounted body was displayed at the institute in the years following (until the facility closed in 2013) and currently at the Silver River Museum.


A jumbo alligator was caught by the Miccosukee Native American tribe's former chief James Billie. When Billie encountered the big bull in an Everglades swamp, so the story goes, he startlingly exclaimed, "That's Superman!". The name stuck. While the animal's length has never been formally confirmed, a source connected to the exhibitor told this author that the alligator measured 13ft-7.75 in/ 4.2m when captured. "Superman" was exhibited at Billie's wildlife park until the reptile died in January 2005 after being relocated to another enclosure (the stress of relocation combined with the colder temperature of the time may have been the cause of his demise).


Sensational claims have been circulating the Internet reporting of giant alligators measuring up to 28ft./ 2.6m. The photographs which accompany these stories seem to display an oversized alligator, but the appearance is merely an optical illusion or the subject of a written deception promoted by the respective claimant. These reports have been publicly dubunked by simple fact-checking efforts. It should be stated that there is no valid reason to believe that the alligator, perhaps the most studied of all reptiles, can reach such enormous size. One such false report is addressed in the "Diet" section herein.


Gallery of Big 'Gators

Ross Allen and the alligator 'Big George'.

This iconic image from the 1950s shows "Big George", perhaps the largest
alligator ever kept in the care of humans. Here he is lunging at his keeper,
herpetologist Ross Allen.
  (Image: Rena Starling/ Ross Allen's Reptile Institute.)

'Superman" the alligator.

"Superman" was photographed here with a keeper in 2004. The 'gator was
taken from an Everglades area swamp. He died in January 2005.

'Goliath" the alligator.

"Goliath" well lives up to his name, at nearly 13ft./ 4m in length; his
enormous mass dwarfs a 6ft./ 1.8m- long female behind him, at an
attraction in central Florida.


SKIN. Alligators begin life outside the egg in a hide of distinctive patterns of variations of yellow, brown and black, and tend to lose color as they grow older, affected by solar burn, water tannins and other environmental factors. The result may be a hide of black, gray, brown, or a combination of such. Some believe that alligators are green, but the green color seen on some alligators is only from a covering of algae, duckweed or other vegetation (refer to the photo at the opening of this article for an example). The dark coloration may be an adaptation that serves to efficiently absorb heat, being that most of the reptile's range is in the temperate range. The bands and spots serve as camoflage for the alligator to deceive potential predators, especialy effective in dark water.


An aligator emerges from the water.The alligator is sometimes depicted as having green skin, though it does not. Any green seen on the alligator is vegetative, such as algae or duckweed, as seen here. 

(Image: © istockphoto/AndreAshby)


The alligator is one of the most heavily armored animals of them all. Thick bony tiles on its neck, back and tail, called osteoderms (see "Temperature Regulation", below), help protect it from attacks by other animals, and have even been known to deflect bullets from some lesser powered guns.                                                      


DENTITION. Teeth number just more than 70 in an alligator, and, being a polyphyodont, it will generate new ones throughout its life, totalling in the hundreds or thousands. Unlike a crocodile, its lower teeth typically fit into indentations in the upper jaw when the mouth is closed, revealing fewer teeth. The teeth are conical, being more pointed in younger animals. The tooth shape is necessary especially for grasping and tearing, since crocodilians cannot chew- that is, pivot the jaw from side to side.


The shed teeth of an American alligator.The teeth seen at right (a U. S. penny is shown for scale) were naturally shed over several months by a captive alligator measuring more than 13ft/ 4m in length. A crocodilian sheds teeth throughout its lifetime, with new ones, stacked conically, growing and ready just underneath. The largest tooth pictured is 1.6in/ 4cm long.An alligator tooth protruding form the jaw.



In the image below one can clearly see a younger tooth protruding from the alveoli (the "gums") of the alligator, where an older tooth was shed.


JAWS. Crocodilian jaws are known as the most powerful in all of the animal kingdom. Bite force is measured in pounds per square inch (PSI). Consider the following approximate maximum measurements. Human: 170; African lion: 970; Dusky shark: 300; hyena: 1,000; alligator: 3,000 (2,982 is the actual record). A 2012 study reports that the Saltwater Crocodile (Crocodylus porosus), seems to have a greater bite force.


Some believe that the crocodilian opens both jaws (on “hinges”), a popular belief based on folklore. The alligator has one jaw, or mandible, the piece on the bottom, and when it opens its mouth to breathe, eat, bite and vocalize, it merely flexes its mandible (bottom section of skull) and, if desired, tilts its cranium (top section) - exactly as humans do.

A vintage postcard depicitng an large alligator with its jaws agape. 


"Drop in any time": The image at right is from a postcard sensationally advertising the intimidating maw of an  'exotic' Florida inhabitant. (Image: Public domain,)


The tongue inside resting in the lower jaw does not extend from the alligators mouth like ours does, but it is good for holding food, and for mother 'gator to carry her babies comfortably in her mouth. The tongue also has the all-important taste buds like ours do.


Integumentary sense receptors.The tiny dark dots on the 'gator's jaw look like freckles but they're actually very sensitive buttons called integumentary sensory organs (see image at left). These enable the animal to sense movement in the water, such as fish swimming nearby. This field of receptors lining the jaws is just another adaptation that makes the alligator such a superb hunter. Interestingly, the crocodile has these receptors all over its body. You may learn more on this subject in the "Ethology" and "Reproduction" sections.


VISION.  Alligators see quite well at night, due to the tapetum lucidum, a structure beneath its array of light receptors in the retina of the eyeball that enhances light reflection. This also gives the alligator its famous reddish-orange reflection in the dark when light is shined on it (see the image below). The pupil of the eye opens to a large circle in darkness(in order to catch as much light as possible), and to a cat-eye-like slit in the light. However, the eyes become darker in appearance when the alligator grows larger.


Alligators eyes shining like hot coals.This image dramatically displays the orange glow reflected in the tapetum lucidum of the orbit (eyeball). (Image: © istockphoto/LarryLynch)


An alligator wears 'swimming goggles'. Its 'third eyelid' is called the nictitating membrane, which closes horizontally over its eye as it submerges, giving the animal an opaque view underwater while protecting the eye.


The alligator does not "blink" constantly as humans and other animals do in order to lubricate the orbit (eye), and the reptile's eyes may stay open for relatively long periods of time. Alligators have been observed closing the eyes when wind strikes them, or closing only the one on the side of the head at which wind is blowing. They also close the eyes during sleep.


You may have heard or read of crocodilians shedding tears, and folklore describes this condition as a result of the animal's remorse for having eaten another animal. Not so, as reptiles have no known capacity for emotion -- at least not in the sense of that of sentient animals and humans -- or nuanced rationalization, such as guilt or regret. Alligator handlers frequently witness these 'tears' when the reptile is under physical stress, such as in combat, while being captured, or even in the excitement and agression of feeding. A study of this seeming phenomenon revealed that the tears may be the result of the air pressure from the reptile's hissing and puffing forced from the sinus canal into its lacrimal (tear) glands and forcing drips of natural tear liquid from the eye.


HEARING. The ear, is located on the surface of each side of the cranial table just behind the eye. Instead of an outward "flap" like a humans' it is a slit-like flap that he animal will close tightly when it submerges. It can hear within a range of 10-15 kHz, similar to mammals and birds.


RESPIRATION. The alligator can breathe even when it is almost completely submerged, thanks to those two small, curved slits on the upper plane near the tip of the snout. and to the palatal valve located at the throat's entrance, all of which can close tightly to seal out water intrusion. Alligator breathing canals work just as a human's does. It breathes through nostrils and through their throats. An alligator can hold its breath for a long time under water, maybe as long as three hours. Interestingly, the alligator has a septum, a bony division between the nostrils (similar to humans), but crocodiles do not. When the crocodilian is in water hydrostatis pressure renders breathing more difficult and energy-consuming than if on land.


CARDIOVASCULAR SYSTEM. The heart of an alligator is a significant feature because unlike almost every other reptile, the organ has four chambers. This complexity enables the cardiovascular system to divert oxygenated blood to the brain to keep it activated (thus keeping the animal alive), enabling the 'gator to hold its breath for long periods, and even to practically "shut down" its brain during brumation (reptilian "hibernation") in the colder parts of its natural range. Under freezing conditions, its "icing response" includes lying in torpor in the frozen water, bringing its heart rate down to a few beats per minute or fewer, compared to an average of 31 in a normal, minimally-stimulated alligator. (If you'd like to read in more depth on this particular subject and view a striking photograph of a brumating alligator, you may enjoy this article.) The cardiovascular system can also divert carbon dioxide-rich blood to the stomach to increase the efficiency of digestion after an alligator has taken in a meal. The system can also separate oxygenated blood from deoxygentated and send the former to the brain- enabling the animal to remain submerged (as discussed above).


Scientists are just starting to learn how powerful alligator blood is in resisting infection and disease. An alligator may swim in foul water, or sustain a gaping wound from combat, but in many cases survives. Proteins in its blood fight infectious intruders to the body (learn more in the section, "Cultural & Commercial Impact,")


FEET. The alligator has five "fingers" on each front foot and four "toes" on each rear one. Claws on the feet may appear menacing, but they are not sharp, compared to a cat or a bird. They are mostly used for touch and, as they are webbed, for slow paddling and steering in water; mother gator will use those claws for scraping mud and vegetation when building or enhancing her nest.


TAIL. The very powerful tail is used mostly for swimming, being used as a rudder and a power "motor" as it is flexed in an "S" motion. The tail is generally flat, as many fish bodies are, in order to streamline movement for efficiency, and to generate powerful water resistance. The "keels" or "whorls" atop the length of the tail allow the non-displaced water to flow more efficiently over the tail as it undulates laterally. The tail is also used for propelling the alligator upward, such as when attempting to snatch prey from an overhanging tree branch. In shallow water the tail may be pressed against the water bed and then forced into flexion, launching the alligator body from the water; this kind of behavior is often seen at various zoos and parks where captive alligators are fed from over the water (A good example of this may be seen in an image in the section, "Cultural & Commercial Impact"). The alligator may also use this for other instances, such as in attempting to scale a barrier (natural, as in dense high brush, or artificial, as in a fence).


The tail can also be very dangerous to any attacker, including a human; the tail of a large alligator whipping at high force could snap an adult human's leg bones.


DIGESTIVE SYSTEM. Please refer to the "Diet" section to learn more about the operation of the digestive system.



A jar of Tabasco sauce.What does this pepper sauce and the world's largest alligator have closely in common?


The son of the inventor of Tabasco sauce was E. L. McIlhenny, who happened to be one of America's foremost naturalists, recorded the two largest known alligators ever reported – and he literally wrote the book on gators back in 1938; you may download a free copy of it, here.




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