The most famous resident of the bayou this week we’re looking at the American alligator. Larger, vocal, and armoured they have become synonymous with the southeast of the United States with them being the state reptile for Florida, Louisiana, and Mississippi.
Taxonomy and Evolution
The American alligator has the scientific name Alligator mississippiensis and is one of two members of the genus Alligator – the other being the much smaller Chinese alligator. Alligators originally evolved in the Americas around 40 million years ago and made their way to the Americas via the Bering Land Bridge, and when the bridge vanished the alligator populations were separated. Over thirty million years before that alligators had diverged from their closest living relatives, the caiman, and they are today part of the family Alligatoridae. They belong to the wider order of reptiles called Crocodilia which consists of crocodiles, alligators, and gharials. How do you tell the difference between an alligator and a crocodile? Other than geographic ranges the skull is the best place to spot the difference. Alligators have a rounded u-shaped snout whereas crocodiles have a more pointed v-shaped snout. If they have their mouths closed you will be unable to see the teeth of alligators while crocodiles have a visible teeth. Alligators are also not as aggressive as crocodiles – alligator wrestling has been a sport first practiced by Native Americans and later US Southerners, something far more dangerous with crocodiles. Although wrestling an alligator is still a very dangerous thing to do, it is like jumping from a first storey window instead of a second storey window.
Biology and Behaviour
American alligators can reach massive sizes with them easily reaching 5 metres (16 feet) in length, although larger alligators have been recorded. They can reach weights of around 300 kilograms (660 pounds) with males generally being larger than the females. Other than that there is little noticeable differences between male and female alligators. This makes them the sixth largest reptile in the world, exceeded only by some of the largest crocodiles. They also have one of the strongest bite forces of all animals have a force exceeding 2,000 psi – we have one of 162 psi – only exceeded by the saltwater crocodile. Alligators have stronger bite forces than hippos, great whites, hyenas, and polar bears! To top off this bite force they have 80 conical teeth which they replace throughout their life, and can go through 3,000 during this time. Like other crocodilians American alligators are covered in hard scales called scutes giving them a lot of protection that only become harder as they age.
Alligators are solitary but social. They often congregate in large numbers, especially when young, but are content being by themselves. During breeding season the males can get territorial. This happens April to May when males make deep bellowing roars coming from the back of their throat to attract females. After mating the females will make a large nest out of vegetation – 3 metres by 1 metres – which they lay 20 to 50 eggs in. The temperature in the nest is very important for many reptiles, alligators included, as it determines the sex of the hatchlings – if it is below 31 degrees Celsius or above 32.5 degrees Celsius most, if not all, the hatchlings will be female, but if it is 32 degrees Celsius then 75% of the nest will be male. By August the eggs hatch, the chicks make high pitch chirps which alerts mum that her babies have hatched, so she will dig them out and gently pick them up in her mouth to take them to the water. Females are most aggressive when they have the nest and hatchlings, lunging at things that come too close if they are not put off by hisses. After a year the hatchlings go on their own, getting larger until they reach maturity – they reach maturity based on size, not age, and this is at 1.83 metres. This takes about a decade to do. From there alligators keep growing if they have space and food and have a very long lifespan – on average they reach 50 years, although ages exceeding 70 have been recorded.
American alligators are most active at night coming onto the land and more actively hunting. During the day they bask in the sun or bob in the water – their nostrils and eyes being on the top of their head allows them to remain submerged while allowing them to see and smell. Their snout is covered in very precise sensors which they use to detect pheromones and movement which helps them both hunt and communicate. They are very vocal crocodilians using a variety of hisses, bellows, chirps, and roars to communicate with one another where zoologists have found out that these calls are individualised. When on the land their walk is unique. Unlike lizards they can do a ‘high walk’, keeping their legs under their body giving them a faster speed that can turn into a fast ‘gallop’. While they do not hibernate in cold temperatures they can go into a state of dormancy; building themselves tunnels they go inside and enter a state of very low metabolism. These tunnels also serve for hot weather as a way to help them cool down.
Distribution and Habitat
American alligators are only found in one part of the world – the US southeast. Alligators stretch from the eastern Texas to the coast and up to North Carolina and Oklahoma. They are most common in the states of Mississippi, Florida, and Louisiana, hence the name Alligator mississippiensis. Alligators are found in freshwater lakes, swamps, wetlands, and rivers, although some have been found in more brackish water. The Everglades in Florida is perhaps the best place to spot wild alligators – being a protected area it allows the alligators to live undisturbed. Despite the urban legends they are not found in sewers – at most they might be found in storm drains in Florida and Louisiana.
Diet and Predators
Alligators are apex predators and often are at the top of the food chain. Depending on their location their diet does change – in the more waterlogged territory of the Everglades they are found to eat more fish compared to the Texan ‘gators. Fish, turtles, birds, lizards, snakes, raccoons, frogs, boar, and even bull sharks and bobcats have all been eaten by alligators. Being unable to tear or chew alligators instead crush their food with their powerful jaws – easily being able to crush the shells of turtles – swallowing the crushed remains. Very interestingly they have used sticks to entice birds looking for foliage to make their nests. Looking like a floating log they rest sticks on their snout so when a bird comes swooping down with one snap the alligator gets an easy meal. Adult alligators do not really have any predators, but they do have competitors. They sometimes share their habitat with bull sharks and American crocodiles, (who both live in brackish water in south Florida), but introduced Burmese pythons also compete with them. Young alligators, hatchlings, and eggs can be eaten by snakes, lizards, birds, raccoons, and large fish. A 2013 paper did find that alligators would sometimes eat fruit, serving as another important vessel for transporting seeds.
Conservation and Threats
We are lucky that these amazing animals are thankfully classified as ‘Least Concern’ meaning they are not endangered. Things were not as positive as this rating – hunters wiped out alligators seeing them as a pest or to use their hide. So much so that they were wiped out further north – until the twentieth-century they were found as far north as Virginia. The setting up of nature reserves and placing alligators under the protection of legislation gave them some opportunity to bounce back. However, they are not in the all clear. Irresponsible pet owners released Nile monitors and Burmese pythons into the Everglades creating competitors that they never once had. On top of this climate change could easily cause their habitat to dry out or flood (which stops them from building nests) and rising temperatures impacts the sex ratio in nests. Unfortunately alligators are found in the arch-conservative Republican states, mainly Ron DeSantis’ Florida, whose desire to repeal wildlife conservation legislation in the name of profit putting alligators at risk once again.
Bibliography:
- Chris Mattison, Nature Guide: Snakes and Other Reptiles and Amphibians, (New York, NY: DK, 2014)
- Don Wilson, (ed.), Wildlife of the World, (New York, NY: DK, 2015)
- S. G. Platt, R. M. Elsey, H. Liu, T. R. Rainwater, J. C. Nifong, A. E. Rosenblatt, M. R. Heithaus, and F. J. Mazzotti, ‘Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?’, Journal of Zoology, 291:2, (2013), 87-99
- Gregory M. Erickson, A. Kristopher Lappin, Trevor Parker, and Kent A. Vliet, ‘Comparison of bite-force performance between long-term captive and wild American alligators (Alligator mississippiensis)’, Journal of Zoology, 262:1, (2004), 21-28
- Katharyn Seay, ‘Alligator mississippiensis‘, Animal Diversity Web, (2019), [Accessed 13/03/2024]
- ‘American alligator’, Smithsonian Zoo, [Accessed 13/03/2024]
- Thomas Rejsenhus Jensen, Andrey Anikin, Mathias Osvath, and Stephan A. Reber, ‘Knowing a fellow by their bellow: acoustic individuality in the bellows of the American alligator’, Animal Behaviour, 207, (2024), 157-167
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