Hunters below the Water’s Surface: American Alligators

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Deep within the confines of a swamp, a lone deer approaches a nearby body of water to quench its thirst. Separated from its herd and vulnerable by itself, the wary animal attentively scans its surroundings for any predators. The isolated creature has managed to escape the jaws of several hungry bears and cougars throughout its days, and is especially cautious in its solitary state. A good look around the area assures the deer that no dangerous animals are within sight and it proceeds to drink. Yet there are dangerous predators nearby. Below the water’s surface, a cold-blooded hunter has detected the deer’s presence through the ripples in the water caused by the deer as it drinks. Not about to let this opportunity slip away, the submerged predator prepares itself for an ambush attack. Above the water’s surface, the deer ceases its drinking in order to check its surroundings once more. Again, there appears to be no danger in sight. Suddenly, the water explodes in front of the deer and, before it can react, powerful jaws brimming with fearsome teeth slam down onto one of the mammal’s forelegs. The attacker’s appearance can be momentarily seen amidst the violently dispersing water. It is unlike many other predators the deer has encountered, with its long, broad jaws, scaly bulk, and massive tail. Yet as soon as the aggressor makes its appearance known it swings the seized deer into the water, causing another large splash which obscures the scene once again. Both animals disappear into the dark waters of the swamp, which soon returns to its previously placid state. Moments later, a figure partially emerges from the water, holding the now lifeless deer in its jaws. Resembling a floating log as it slowly swims to a deeper section of the swamp, this powerful reptile has dragged many other creatures to a watery grave over the course of its life. Its aggressive nature, large size, and superior might have allowed it to become the top predator of the swamps. It is the ruler of this dangerous habitat and among the largest of all reptiles. This deadly ambush predator is the American alligator.

Photograph credit:

American alligators (Alligator mississippiensis) are among the largest predators in North America, capable of reaching up to 15 feet in length and 1000 lbs in weight.[1] As such, they are much larger than the only other living alligator species, the Chinese alligator (Alligator sinensis).[2] Their bulky bodies make it difficult for them to move around on land, as their small (though fairly powerful) legs usually cannot carry them too far before they tire out. However, their webbed feet and powerful tails make them excellent swimmers as well as formidable predators in the water. Alligators, like all other crocodilians, possess a rough and scaly hide which provides protection against other potentially dangerous animals.[3] Since the waters that these predators thrive in are usually dirty, they possess nictitating membranes over their eyes which function similarly to water goggles, protecting their eyes when they submerge. Instead of relying on vision when hunting underwater, alligators are said to respond to vibrations or pressure changes created by prey moving in the water. These vibrations travel through the water and are sensed by the large reptile, alerting it to the potential target’s location.[4] The alligator can then search for the animal and kill it using its powerful jaws (crocodilians can slam their jaws shut with more power than any other animal) or drown it by pulling it under the water’s surface.

Adult alligators can reach 15 feet in length and weigh up to half a ton. Photograph Credit:

Though similar in appearance to their relatives, the crocodiles, alligators possess several characteristics which separate them from their more numerous cousins. Alligators are generally dark-colored, possess broad, rounded snouts, and usually prefer freshwater habitats. On the other hand, crocodiles are mostly of a grayish-green coloration and are normally found in coastal, brackish, and saltwater habitats. They possess narrow, tapered, triangular snouts as opposed to the alligators’ wider jaws. Interestingly, the fourth tooth on either side of an alligator’s lower jaw fits into an internal pocket in the upper jaw designed to hide these teeth when the jaws are closed. This is not the case with crocodiles, where the fourth tooth is always exposed.[5]

Alligators possess broad jaws, a feature which differentiates them from crocodiles. Photograph Credit: Dr. Jerry Gingerich

Alligators occur throughout the southeastern United States and are especially numerous in Florida and Louisiana. As stated before, they prefer freshwater habitats, commonly residing in the rivers, lakes, swamps, and marshes present throughout their range.[6] They will, however, occasionally enter brackish waters around mangrove swamps. Despite not possessing buccal salt-secreting glands like their crocodile cousins (which, as a result, thrive in saline water), alligators can temporarily tolerate the increased salinity in these habitats.[7]

Alligators feed on a wide variety of animals. Young alligators mainly prey on frogs, small fish, and invertebrates and progress to larger animals as they grow. As full grown adults, alligators can tackle any animal which dares to enter their domain, making them the apex predators of their range. However, relatively small animals always make up a large portion of the alligator’s diet, with common prey including fish, turtles, small mammals, birds, and reptiles (including other alligators). Alligators are opportunistic feeders and will consume carrion if it is available to them.[8] As both apex predators and scavengers, alligators possess an essential role in their environment. Their consumption of carrion lowers the chances of disease spreading throughout the environment, while their predation on many species results in the moderation of prey populations, allowing no species to truly overpopulate.[9]

Alligators are slow and somewhat clumsy on land yet swift and deadly when in water. Photograph Credit: James Dowling-Healey

Their predatory instincts and great strength can sometimes get them into trouble, though, as many alligators will incorporate dogs and other family pets into their diet when they travel closer to human-populated areas. On rare occasions, large alligators will also attack and kill children and even adults. Although reasons for these attacks can vary, many are the result of people provoking alligators into aggression or feeding the alligators (thus making the large reptiles associate humans with food).[10] This has led them to become notorious creatures which are hated by some people. On occasions, alligators will react aggressively to humans (or any other creature) with little to no provocation, though many alligators are, ironically, very shy. Ultimately, the best way to prevent an alligator attack is to simply avoid interacting with the animals and keeping a good distance away from them.

Though alligators rely on brute force to take down their prey (as many large predators do), their method of locating prey through the target’s movement in water is quite uncommon. The secret to this style of hunting could possibly lie in integumentary sense organs which all crocodilians possess. Though the sense organs are present only on the jaws and heads of alligators and caimans, they can be found throughout the bodies of crocodiles and gharials. The specific distribution of these sense organs varies from one species to another, most likely due to somewhat different functions depending on each species’ natural environment. As their name suggests, these integumentary sense organs are found only in the skin layer of the animals, and can be observed as small pigmented spots located on the outer edges of the crocodilians’ scales (a single scale can hold up to four sensory pits, though it is much more common to find only one per each scale). In reality, the functions of these sensory organs have yet to be determined, though there are several possible theories. The sense organs located around the jaws are probably mechanoreceptors which can detect pressure changes in the water. As animals swim in the water, their movements create pressure waves which impinge on the crocodilians’ sense organs and fire them. The wave of firing across the reptiles’ heads may alert them to where the pressure waves are coming from, leading the predators to the location of their prey. The sense organs can also help the crocodilians compensate for the poor visibility in the dirty waters of swamps and similar habitats. As an alligator searches for food underwater, objects such as rocks and pebbles will not elicit a biting response. A piece of meat or a living animal, however, will probably cause the alligator to react with a bite. Yet why do alligators and caimans only possess these organs on their heads and jaws while their cousins possess them throughout their body? It is possible that the sense organs located throughout the bodies of crocodiles and gharials may be involved in salinity assessment (which would explain their absence in alligators and caimans, considering they do not possess the salt glands present in both crocodiles and gharials). However, there is no evidence to support this function.[11]

A mother alligator with her offspring. Photograph Credit:

The possible combination of sensory organs and immense strength may make alligators seem invincible, but even apex predators encounter danger throughout their lives. Hatchlings and juvenile alligators are vulnerable to attacks from dozens of predators, including birds, raccoons, bobcats, and other alligators.[12] Adult alligators are generally free of predators (apart from humans), though the invasive Burmese python (Python molurus bivittatus) will occasionally prey on alligators.[13] Alligators will also prey on Burmese pythons, and it is not very rare to encounter both animals locked in struggles with each other.

A Burmese python and an American alligator locked in a struggle. Both species are known to prey on each other. Photograph Credit: Lori Oberhofer, National Park Service

Breeding takes place after temperatures rise during the spring, though it may also take place earlier in the alligators’ southernmost range, where temperatures rise earlier in the year, and breeding may not even take place at all within the most northerly populations. Both sexes take part in courtship rituals, which include low-frequency bellowing (which produce vibrations that travel considerable distances), slapping the water’s surface with their heads or jaws, and releasing odor from paired musk glands everted from under the chin and from the cloaca. Once courtship nears its end, pairs will engage in bouts of snout and back rubbing. These courtship rituals can last several hours and are thought to help synchronize spermatogenesis (the production of sperm) and ovulation (the release of eggs from the ovaries).[14]

Female alligators begin constructing mound nests at the start of summer, when it is both damp and warm. The nests are created from a combination of freshly torn vegetation and mud, and are usually situated on banks and mats of vegetation. These nests can be quite large, rising 3.5 feet high and being twice as wide. This is to prevent the eggs from being flooded when water levels rise. The exact site where a nest is constructed can depend on a number of factors, as chosen by the female alligator. Many alligators use the same nest locations from year to year, and these nests are sometimes close to holes dug by females to rest in. Once she chooses her location and finishes building a mound, she will excavate a conical depression at the top of the nest using her back feet and lay anywhere from 20 to 50 eggs inside. She then covers the hole with more vegetation, using her legs to scoop the material into the hole of the mound. Some females abandon completed mounds before beginning to lay their eggs. Reasons for this can vary; perhaps they are not satisfied with the nest locations, or felt stressed from the presence of nearby alligators. Whatever the reasons, there are females which will also take advantage of these abandoned nest sites, using them to lay their own egg clutches. The female alligators remain near the nests to protect them, usually residing in nearby water or shelters that they dig for themselves (named “alligator holes”). If a threat comes too close to the nest, the female immediately rushes to the protection of her precious eggs, scaring away or killing the intruder. After about 65 days (the incubation period of the eggs can vary depending on temperature), the eggs are finally ready to hatch and the young alligators call out from the nest. Their calls alert the mother, which then proceeds to dig out the nest (her presence is sometimes necessary in order to break apart the hardened mud and vegetation covering the eggs). After breaking apart the mound, she gently carries 8-10 of the hatchlings in her mouth down to the water, pushing down her tongue to form a special pouch for the young alligators. Once she enters the water, she opens her jaws and slowly shakes her head side to side, encouraging the babies to swim out. The young alligators remain with their mother for around a year, though they may stay with her for a longer period of time. They will need her protection at this vulnerable stage in their lives. When the young alligators feel threatened they call out to their mothers, which will respond swiftly and aggressively to the threat. The young alligators remain in pods (which can include alligators from other nests) during this stage in life, affording them safety in numbers along with the protection their mother provides them with.[15] Though their chances for survival are small, this family-style behavior usually guarantees that at least some of the hatchlings survive to adulthood. If the hatchlings can survive this early yet dangerous stage in their lives, they will one day become the dominant predators of their world and can enjoy a long lifespan which can exceed 60 years.[16]

Most young alligators die before reaching adulthood. Those which survive and attain adult size become the dominant predators of their habitat. Photograph Credit:

Though alligators now possess a stable and healthy population, they were once heavily hunted for their meat and skin, which was useful for creating leathery goods. Before alligator hunting was controlled in 1970, an estimated 10,000,000 alligators were killed for their skins. This ignorant excess in hunting nearly led to the extinction of the American alligator. Fortunately, conservation efforts saved the species from extinction, and it is no longer classified as endangered.[17]

Although notorious for their potential danger and occasional attacks on humans, alligators are understood as fascinating and important animals by those who study them. As both apex predators and scavengers, they are a vital species for the maintenance of their ecosystem’s health. They are marvelously designed hunters, capable of locating prey by unconventional means which are yet to be entirely understood. They are incredibly powerful and are the dominant hunters throughout their range. Despite the fact that the American alligator was nearly hunted to extinction several decades ago, conservation efforts were able to save the species and the population eventually reverted back to a healthy state. Now numerous and widespread, these amazing reptiles can be observed in their natural environment, fulfilling their role as the swamp’s mighty apex predators.

[1] “American Alligator.” Available from Internet; accessed 20 June 2011.

[2] “Chinese Alligator.” Available from Internet; accessed 20 June 2011.

[3] “AMERICAN ALLIGATOR.” Available from Internet; accessed 20 June 2011.

[4] “American Alligator (Alligator mississippiensis).” Available from Internet; accessed 20 June 2011.

[5] “AMERICAN ALLIGATOR.” Available from Internet; accessed 20 June 2011.

[6] “American Alligator.” Available from Internet; accessed 20 June 2011.

[7] “Alligator mississippiensis.” Available from Internet; accessed 20 June 2011.

[8] Ibid

[9] “American Alligator.” Available from Internet; accessed 20 June 2011.

[10] “Alligator mississippiensis.” Available from Internet; accessed 20 June 2011.

[11] “Integumentary Sense Organs.” Available from Internet; accessed 21 June 2011.

[12] “American Alligator.” Available from Internet; accessed 21 June 2011.

[13] “Burmese Python: Species Profile.” Available from Internet; accessed 21 June 2011.

[14] “Alligator mississippiensis.” Available from Internet; accessed 20 June 2011.

[15] Ibid

[16] “American Alligator (Alligator mississippiensis).” Available from Internet; accessed 21 June 2011.

[17] “American Alligator.” Available from Internet; accessed 21 June 2011.

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On June 21, 2011
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