Draft #2: Alligators of the Everglades

This discussion topic submitted by Melody D. Moorehead ( mmoorehead@kingslocal.k12.oh.us) at 10:11 pm on 5/2/01. Additions were last made on Saturday, May 4, 2002.

Alligators of the Everglades
By: Melody D. Moorehead

For thousands of years, there has been an important, if somewhat strained, relationship between humans and alligators. The earliest human inhabitants of the southeastern United States hunted alligators for their hides and meat. Early Spanish explorers were awed by this giant reptile, naming it “El lagarto,” the lizard. “El lagarto” eventually became “alligator,” and this amazing creature continued to become woven into the local culture, inspiring legends of magical powers and phenomenal size. The American alligator, Alligator mississippiensis, is a reclusive monster that often strikes fear into the hearts of many. However, this often misunderstood part of the Florida Everglades population has become an integral part of the local ecology and economy.
Fossil records indicate that evolution has left these reptilian giants mostly unchanged since the Triassic period, nearly 200 million years ago. Alligators and their cousin crocodiles belong to the ancient Order Crocodilia. Modern crocodilians are the only surviving reptiles of the archosaurian lineage that gave rise to the great Mesozoic radiation of dinosaurs and their kin, and to the birds (8). Modern day dinosaurs, crocodilians comprise four distinct groups: alligators, crocodiles, caimans, and gharials. Of the four, only one species of alligator, Alligator mississippiensis, and one species of crocodile, Crocodylus acutus, can be found in the United States.
The anatomy and physiology of the American alligator is the “stuff” legends are made of. Hatchling reptiles enter the world a mere 6-8 inches, and can grow to an amazing 13 feet, 600 pounds. The largest gator ever recorded, a whopping 19’2”, was captured in Louisiana (1). Louisiana gators tend to have a better food supply and a larger resulting size. Alligators are equipped with an elongated, robust, well-reinforced skull, brimming with pearly whites. An adult gator has 80 sharp teeth in its mouth at one time, which are replaced as they wear down. In fact, an alligator may go through 3,000 teeth in a lifetime (3). Massive jaw musculature helps to give these reptiles a crushing power of 3,000 psi (6).
The alligator’s resilient integument contributed to early legends of magical powers. This extremely tough skin is armored with bony plates, called scutes, which may prevent snake fang penetration. Unfortunately for the alligator, this legendary “immunity to snake bites” fueled early hunting of gators for their teeth, to be used as protective charms (6). The color of this tough hide is grayish black on adult gators, although the young may have yellow or white highlights on a black body. Gators have four short legs, with five toes on the front feet, and four on the rear. Using a “high walk” technique, they can run on their toes with their tails lifted up off the ground attaining speeds of up to 30 mph (1).
Gators also have unique respiratory and vocalization abilities. A specialized valve in the throat, the glottis, enables the capture of prey under water, but the gator must raise its head above water in order to swallow (6). A complete secondary palate allows the gator to breathe when its mouth is filled with water or food. Alligators are unique among reptiles in their ability to make definite vocalizations. The male produces loud bellows during mating season, and young hatchlings call to mother gator for help in escaping the nest.
Physical differences are evident between alligators and crocodiles. Alligators have short, rounded, blunt snouts, and grayish black hides. Crocs have long tapered snouts, more protruding teeth, and light tan to brownish hides. Though alligators are very powerful, they are less aggressive than crocs. In fact, two species of crocodiles are known to be man eaters, the salt-water crocodile and the Nile crocodile (6). Luckily, neither inhabit the United States.
So where exactly do these “lizards” call home? The American alligator can be found only in the southeastern United States from the Carolinas down to Florida and as far west as Texas. The highest populations of gators occur in Florida and Louisiana. Gators will inhabit fresh water to brackish areas, and occasionally salt water, though not for long. They do not possess the salt extracting glands of crocs. The most common places to find gators are swamps, marshes, lakes, and drainage canals. Male gators prefer deeper water year round, while female or juvenile gators (under 4 feet in length) prefer protective, highly vegetated, marshy rivers and lakes. It has been estimated that 1,000,000 wild alligators inhabit Florida alone (6). Southern Florida is the only place in the world where both gators and crocs can be found together (1).
Alligators are carnivorous reptiles, and nocturnal feeders. Smaller gators feed on snails, frogs, insects and small fish. Large gators have a diet that may also include turtles, snakes, birds, small mammals, and even other gators. Because gator teeth are made for grabbing and holding, not cutting, gators have developed some remarkable “dining skills.” A gator will envelop large prey in a “dance of death,” grabbing hold of the victim with powerful jaws and rolling underwater to submerge and drown its prey. Because food must be swallowed whole, a gator may slap its victim against the shore or water in order to tear off a piece of flesh small enough to swallow. Better yet, dead prey may be dragged around or guarded for several days until the meat rots enough to be ripped apart. Some gators have even been known to hold food in their mouths until it deteriorates enough to be swallowed (6). A huge advantage of being an exotherm is requiring less energy, and therefore, less food. An adult gator can survive many months without a meal (1).
The alligator’s reproductive habits begin with a complex courtship in April and May. Gators will engage in snout-touching, bellowing, back-rubbing, circling, and swimming together. They will even test one another’s strength by gently trying to press each other under water (1). Nesting occurs in June and July as female gators build vegetative nests above the water line. Nests are then filled with an average of 30-45 eggs. Because of high rates of nest raiding, mostly by raccoons, an egg survival rate of 50% is considered normal (2). Eggs will incubate for about 65 days, as chemical breakdown of nest material keeps the eggs warm. Sex of the offspring is temperature dependent. Temperatures below 86 F will produce all females, above 93 F will produce all males, and temperatures in-between will produce both sexes. Upon leaving the eggs, hatchlings make high-pitched vocalizations to alert mother gator, who promptly digs her youngsters out and sometimes helps to transport them to water.
Upon leaving the nest, this magnificent reptile’s chink in the armor becomes apparent. The developmental stages of an alligator’s early life are filled with extreme danger. Even though mother gator keeps a close guard on the hatchlings for up to two years, over 80% of juveniles become meals for wading birds, raccoons, bobcats, otters, snakes, large bass, and even large gators (2). Surviving juveniles will remain close to the nesting site in small groups, or pods, until they reach sexual maturity. For gators, sexual maturity is dependent on size rather than age. Once a gator reaches a length of 4 feet, it is considered an adult, and will venture out into deeper waters – where man is now its only natural predator.
Alligators have played a huge part in developing the ecological balances existing in the Everglades. Holes and trails created by gators in the wet season become the only areas of concentrated water in the dry season. These “gator holes” create a refuge for an abundance of aquatic life, as well as a feeding site for terrestrial creatures and wading birds. It is for this reason that alligators are considered a keystone species, whose well-being reflects the overall health of the ecosystem (12). In 1967, due to human predation, the American alligator was placed on the U.S. Fish and Wildlife Endangered Species List. After a considerable comeback, it was reclassified from endangered to threatened in 1977 (6). In the 1980’s, alligators came to be viewed as a renewable resource, but remain on the USFWS Threatened Species List due to similar appearance to the American crocodile, which is endangered (8). The hope is that by leaving the alligator on the threatened list, the endangered crocodile will not be mistaken for a gator and killed by hunters.
Alligators have become an important part of the economy of Florida, as well as the ecology. Alligator farming produces over 3,000 pounds of meat and 15,000 skins annually (6). Many tourists will pay big bucks to catch a glimpse of a gator on a guided tour of the swamps. Wild gators also feed on trash fish, like gars, which are predators of the bass so heavily prized by the fishing industry. In fact, the alligator became the official state reptile for Florida in 1987.
With nearly 1,000 people moving to Florida daily, there is bound to be more and more gator-human interaction (2). Measures have been taken to protect the citizens from unnecessary encounters. Florida law prohibits feeding of wild gators, as most fatal attacks on humans have occurred when gators have been fed by humans or are protecting their nests. Residents are also advised to avoid swimming after dusk in areas inhabited by large gators. Most reported gator attacks are attacks on pets. From 1973 to 1990, only 127 alligator attacks on humans were reported in Florida, with only 5 being fatal (2). Humans have much less to fear from gators than they should fear from us.
Everglades National Park is the largest remaining subtropical wilderness in the U.S. Human encroachment has threatened this rare ecosystem, and many of its creatures, with extinction (4). Natural cycles of feeding and nesting have been disrupted by diverting water through canals and levees for human use. Numbers of nesting birds have declined 93% (12). Artificially controlled water levels are delivering pulses of water to the park in late June, flooding gator nests and drowning eggs (11). A study in 1994 by Mazzotti and Brandt concluded that the alligator is not doing well in managed marsh systems due to nest failure (10). Pollution has also become a major problem. Researchers at Lake Apopka, near Orlando, found that large amounts of pesticides, DDT and DDE, had spilled into the lake, causing reproductive abnormalities in local gator populations. Exposure to the pesticides has caused alligators in the Everglades to weigh hundreds of pounds less than gators in other parts of the state (9).
The American alligator plays a critical role in the ecology and economy of our most southeastern state. Without this magnificent reptile, the rare and delicate ecological balance of the Everglades would likely collapse. Tourism and the local economy would surely feel the impact. Yet human encroachment continually puts these animals at risk. Hopefully the resilience that has persevered for over 200 million years will continue, so that future generations may be terrified, and at the same time amazed, by the alligators of the Everglades.

References:
1. Alligators: Everglades National Park. http://www.nps.gov/ever/eco/gator
2. The American Alligator. http://www.ifas.ufl.edu/AgriGator
3. Animal Bytes: American Alligator. http://www.seaworld.org/animalbytes/
4. Can the Everglades Survive? http://www.nps.gov/ever/home.htm
5. Endangered Species: Everglades National Park. http://www.nps.gov/ever/eco/danger
6. The Gator Hole. http://home.cfl.rr.com/gatorhole
7. How to Find Alligators. http://fortlauderdale.about.com
8. Integrated Principles of Zoology. Hickman, Roberts, Larson. pp.548-569.
Times Mirror Higher Education Group, Inc. 1997.
9. Pesticides Suspected in Gator Decline. CNN. March 15, 1998
10. Recovery of Regionally Healthy Populations of Endangered, Threatened, Keystone, and Indicator Species of Animals. http://everglades.fiu.edu/taskforce
11. Reptiles and Amphibians: Everglades National Park. www.nps.gov/ever/ed




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