Taxonomy, Phylogeny & Etymology
Distribution & Population
Anatomy & Physiology
Cultural & Commercial Impact
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.
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.
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.
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
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
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.
of the largest
measurements ever reported were by noted Louisiana
naturalist E. L. McIlhenny of a 19ft/ 2in / 5.8m
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
"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"
Gallery of Big 'Gators
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.
Starling/ Ross Allen's Reptile Institute.)
photographed here with a keeper in 2004. The 'gator was
taken from an Everglades area swamp. He died in January 2005.
"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.
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
The alligator is sometimes
depicted as having green skin, though it does not. Any green
on the alligator is vegetative, such as algae or duckweed, as
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
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.
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.
In the image below
one can clearly see a younger tooth protruding from the
(the "gums") of the alligator, where an older tooth was shed.
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.
"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
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.
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.
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.
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
& 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
Please refer to the "Diet"
section to learn more about the operation of the
does this pepper sauce and the
world's largest alligator
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,
on a link from the menu atop this page to navigate this article.
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