American Alligator

Laura Evans Duncan

Introduction

Welcome… to Jurassic Park. Whether you look at them outside in your backyard, along a golf course or in a National Wildlife Refuge, the American alligator is a living piece of history. A true dinosaur. Even though our current day crocodilians do have some prehistoric ancestors in the Jurassic Period, our true long-snouted crocodilians actually began in the Cretaceous Period.

Being the largest reptile in the United States, these awesome creatures can grow 13 feet long – or more – and weight 1,000 pounds. They can live up to 50 years in the wild and have been known to live for 70 years in captivity. These apex predators are often marred in fear and half-truths; misrepresented as only dangerous pests rather than biological wonders and important keystone species. What do these giant reptilians have to offer?

American alligator, Bulls Island, SC

Laura Evans Duncan, May 2020

Slide mark from tail and tracks, Bulls Island, SC

Laura Evans Duncan, May 2020

American alligator tooth, Topsail Beach, NC

Laura Evans Duncan, June 2020

Alligator (top) crocodile (bottom)

(Image: © National Park Service photos by Rodney Cammauf.)

Taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Crocodilia

Family: Alligatoridae

Genus: Alligator

Species: mississippiensis

Common name: American alligator, common alligator, gator

Scientific name: Alligator mississippiensis

American alligators are a member of the order Crocodilia; which includes all alligators, caimans, true crocodiles, and gharial’s (a fish eating crocodile with a long snout from Asian). The family Alligatoridae includes eight individual species such as the Chinese Alligator (Alligator sinensis), Black Caiman (Melanosuchus niger) and Spectacled Caiman (Caiman crocodilus). Only two species of crocodilians are found in the United States: the American alligator and the American crocodile (Crocodylus acutus) which can be found in Florida. The American alligator’s scientific name, Alligator mississippienis, comes from the Spanish word “lagarto” meaning “lizard” in Spanish and “mississippienis” of Latin derivation meaning “of the Mississippi (river)”.

Niche and Habitat

American alligators are primarily found in freshwater environments but can also be found in brackish water; wetlands, rivers, lakes and other small bodies of water. They have occasionally been found along salt water beaches but will usually remain for only a couple of days; lack of a salt gland that is seen in saltwater crocodiles does not enable them to live long-term in saltwater environments. This gland excretes excess salt through their lingual salt glands located on the tongues of crocodiles.

Their range encompasses most of the southeastern United States from North Carolina down along the coast to Texas and as far north as Arkansas. Their inhabitance in wetlands ties directly into their biological roles as apex predator; their predation upon rodents and other mesopredators helps control their populations and as result ends up benefitting many of species in the food web. A mature American alligator has no natural predators other than humans and other alligators. However, juvenile alligators are often predated upon by wading birds, ospreys, snakes, river otters and raccoons. To learn more about their role in ecosystem, benefitted species, and their status as a keystone species, read on in “Environmental Impacts” and “Friends and Foes”.

https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.100172/Alligator_mississippiensis

https://www.coastalreview.org/2013/10/how-many-alligators-in-n-c/

Evolutionary History

Amazingly, today’s American alligator has remained mostly the same for the past 8 million years. Many characteristics have led this creature in becoming the ultimate nocturnal predator it is today. Their strong muscular bodies covered in an armored like “scute” or modified scale and possess massive tails used for navigating and propelling themselves thorough the water. Their eyes, ears, and nostrils are all positioned on the top of its head; allowing for complete awareness without any if its sense being impeded while swimming in the water as the rest of its body stays hidden below the water surface. A thin translucent eyelid, called the nictitating membrane, protects its eyes and acts like a pair of swimming googles under water. Even at night, the tapetum lucidum, a reflective layer behind the retina, reflects light and allows them to see in the cloak of darkness. Its signature feeding style, the “death roll” used to kill its prey, is perfectly formulated for our American alligator. Thanks to the glottis, a palatal fold in the back of their mouth, alligators can hold their prey under water without allowing water into their own trachea.

Two fossils found in the Panama Canal are helping fill the holes in the evolutionary divide between alligators and caimans in the Alligatoridae family. It is thought that a common ancestor from 70 million years ago in North America stayed and became today’s alligators where as another ancestor migrated from North America to South America and evolved into caimans. These two fossils recently found, differentiating in jaw structure and therefore an indicator of different diets, are identified by characteristic such as proportions of the snout, the number of teeth, and characteristics of the dorsal plates and ostedorms (bony structures along the top side of the animal). These discoveries are helping fill the evolutionary tree of the Alligatoridae and Crocodilia taxa.

"Eyeshine" from the tapetum lucidum of an American alligator

https://www.bbc.com/culture/article/20170714-in-the-sightline-of-an-alligator

Environmental Impacts

American alligators are considered a keystone species and have a significant and beneficial impact on its environment. They dig burrows with their tails, claws, and snout to uproot vegetation and sediment within and around the banks of waterways. These wallowed out depressions, called “gator holes”, are used for nesting or to survive during the winter and dry seasons. Sometimes these holes are excavated even deeper into dens; sometimes almost 20 feet deep into the overhead of a water bank. American alligator’s role as “ecosystem engineers” and their burrows are used after the fact for habitat, breeding, or as a water source by many other species such as birds, snakes, turtles, fish and crustaceans.

American alligators have been significantly impacted by humans. After years of overharvesting for commercial use and habitat loss during the early 20^th century, they nearly went extinct. The ventral belly side of their hide was a widely sought after as a high quality leather and led to high hunting pressures. In 1967 the American Alligator was listed as endangered under the Endangered Species Act.

American alligator by cautionary sign on golf course

https://www.eatsleepplaybeaufort.com/lowcountry-gators-enjoy-spring-break-too/

Conservation

Today, there are an estimated 5 million American alligators in the United States due to habitat conservation and population monitoring and regulation from the U.S. Fish and Wildlife Service and other state agencies The American alligator was removed from the list of endangered species in 1987. However, due to the fact that crocodiles and caimans are still endangered, the American alligator is still listed as threatened because of their close appearance.

Another important piece of legislation vital to the alligator’s success was the amendment to add reptiles to the Lacey Act; a 1900 law that banned the trafficking of illegal wildlife. Legally hunted and harvested alligators are still monitored. “Nuisance” alligators who are removed by permitted Nuisance Alligator Agents from areas due to human conflict or possible harm to the public, are often processed and their hide and meat are used or eaten. In 2007, the North Carolina General Assembly passed the law prohibiting the feeding of wild alligators. You can often find informational signs around bodies of water where alligators are known to live saying things like “a fed gator is a dead gator”. When alligators are fed they lose their natural fear of humans and leads to an increase chance of human conflict. Continuing to educate the public on American alligators and emphasizing the need to respect their space it vital to avoid future conflicts.

Friends and Foes

The American alligator is an opportunist predator and will eat almost any animal within its habitat when it needs to feed. Despite this fact, the alligator is more friend than foe to many creatures thanks to its presence. In salt marshes, the alligator feeds heavily on blue crabs. With the control in population of this mesopredator, this in turn leads to less predation for the Periwinkle snail (Littoraria irrorata), an important grazer of Spartina grass and the Atlantic ribbed muscle (Geukensia demissa), a filter-feeder who attaches to the base of Spartina grass and deposits nutrients through fecal matter to stimulate grass growth. The Florida Red-bellied turtle (Chrysemys nelsoni), often nests their own eggs in the habitat created by alligator nest mounds. Wading birds are another species in particular that benefit from the presence of the American alligator. Ibises, storks, spoonbills and herons often select their nesting sites where alligators reside. Their nests are more protected in the presence American alligators who feed on and deter mammalian nest predators like opossums and raccoons. In return, the alligator benefits by feeding on chicks that fall from their nests.

Web Resources for Audience to Explore

https://www.ncwildlife.org/Portals/0/Conserving/documents/Profiles/amalligator-v5.pdf - provides an informational profile and Q&A Resource Section for teachers who want to teach their students about American alligators
https://www.ncwildlife.org/Portals/0/Learning/documents/Species/Alligator/AMP%20Final%202017-10-06.pdf – contains the 2015 North Carolina Alligator Management Plan from the NC Wildlife Resources Commission
https://www.fws.gov/endangered/esa-library/pdf/alligator.pdf - provides a USFWS informational sheet on the American alligator
https://wildlife.onlinelibrary.wiley.com/doi/10.1002/jwmg.21719 -study from the Wildlife Society on the characteristics of American alligator bites on people in Florida
https://myfwc.com/research/wildlife/amphibians-reptiles/alligator/publications/ - Provides links to more scholarly journals/research on the American alligator from the Florida Fish and Wildlife Conservation Commission

Educational Videos

BBC's "Life in Cold Blood"

Steve Irwin, The Crocodile Hunter, "Swimming with Alligators"

Resources

https://www.britannica.com/animal/crocodile-order/Evolution-and-classification
https://www.fws.gov/endangered/esa-library/pdf/alligator.pdf
https://www.nationalgeographic.com/animals/reptiles/a/american-alligator/
http://www.iucncsg.org/pages/Classification-of-Living-Crocodilians.html
https://www.ncwildlife.org/Portals/0/Learning/documents/Species/Alligator/AMP%20Final%202017-10-06.pdf
https://crocodilian.com/cnhc/csp_amis.htm#:~:text=American%20alligator%2C%20Mississippi%20alligator%2C%20Pike,for%20 %22belonging%20to%22).
https://jeb.biologists.org/content/211/9/1482#:~:text=In%20crocodiles%2C%20the%20salt%2Dexcreting,et%20al.%2C%201982).&text=The%20salt%20glands%20appear%20as,half%20of%20the%20lingual%20surface.
https://www.sciencemag.org/news/2013/03/ancient-alligator-ancestors-unearthed
https://www.researchgate.net/publication/254846738_Ribbed_Mussels_and_Spartina_Alterniflora_Production_in_a_New_England_Salt_Marsh

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