American Crocodile (final)

This topic submitted by Michael A. Buch ( MABuch131@aol.com) at 3:22 PM on 6/2/05.

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My discussion topic is on the American Crocodile. I plan on teaching the class about the difference between an American Croc from an American Aligator. About the crocodile's appearnce, range and habitat, food, feeding method, how it is equiped to submerge, mating and nesting, and the threats to it and how we are trying to conserve the remaining populations.
I feel this is an important topic because not too many people know much about the American Crocodile. It is, like many other top-line predators, endanged. It needs our help, and I wish to help educate people about it. The more people know, the more they can respect it.

Here is the paper:

The American Crocodile is a large reptile that is protected by various nations and international law. It is very rare in the United States, and unlike its more popular cousin the American Alligator, it has a much smaller range within the USA. It is the most evolved of all the reptiles, but sadly, it is one of the most threatened too. Work is being done to help ensure that this great predator will remain in the wild for generations to come.
In the United States, the American Alligator is much more popular than the American Crocodile. Many people do not even realize that we have crocodiles in the United States, yet others do not have any idea there is a difference between the two. American Alligators are much more largely dispersed in the United States, which might be a large reason they are better known. Their habitat ranges from the Carolinas along the Atlantic and Gulf coasts to Texas. While the crocodile only lives in the southern tip of Florida. But these animals, while similar, are different. The crocodiles can be distinguished from the alligator “by their longer, more narrow snouts and by their lower teeth, which are visible even when the crocodile's mouth is closed” (2). Some internal differences between the crocodile and the alligator is that the crocodile has the most developed brain and heart of any reptile (6). The heart has two distinct ventricles, while most reptiles only have partially separated ventricles. Another major difference is that the crocodile can live in fresh and brackish water, while the alligator lives mainly in fresh water. The only place that both of these animals coexist is in the Florida Everglades.
The American Crocodile has a very typical appearance for crocodilians. The crocodile can reach large sizes. Adult males have been known to reach seven meters in length, which is almost twenty three feet (5), and they can weigh up to four hundred fifty pounds (2)! Their body style is what is considered to be the typical lizard shape (9), which is long and slender, with short powerful legs that come off the side of the body, and not off the bottom. They have a grey-green appearance with a white-yellow underbelly (9). They have dorsal armor, but it is much more reduced than other species of crocodile (4). The rows of raised scales that run down the crocodile’s back contain dermal bone (1). The juveniles have a banded appearance on their tails, but that slowly disappears as they grow into adults (4). Very old crocodiles have a dull grey appearance (6).
The American Crocodile’s range covers all of Central America, the northern coasts of South America, southern Mexico, Cuba, Jamaica, Hispaniola, and the southern tip of Florida (5). The environments it makes its living in are brackish waters and fresh water environments. It can inhabit rivers, canals, lakes, coastal marshes, estuaries, and coastal lagoons (4). A group of crocodiles have made their home in a very odd spot; “a population occupies the brackish water cooling canals at the Turkey Point nuclear power plant in Florida” (4). In Florida, you are most likely to see a crocodile at the Crocodile Lake National Wildlife Refuge in Key Largo, the Everglades, and Turkey Point (3). The crocodile, even though it is not a marine reptile, has been found far out at sea and has occupied isolated islands throughout the Caribbean (6). This is because crocodiles can travel great distances, which allows them to occasionally end up in odd spots (10).
The American Crocodile is a carnivore and will eat a variety of things. Their diet is primarily fish, but they also consume crabs, insects, amphibians, waterfowl, and small mammals (2). Some of the adults are also known to eat turtles (6); it just depends on the size of the animal on what it eats, “the bigger they are the larger the prey” (9). Crocodiles are occasionally blamed for the loss of domestic pets in more heavily populated regions (4). Although there have been some reports of crocodiles attacking humans, very few of these reports have been authenticated (4). They are not much of a threat to humans “because of their shy and reclusive nature” (3). Thankfully, we are not on their dinner plate. This is in large contrast to the famous Nile Crocodiles, which are very aggressive and dangerous to anyone near one of them. Another reason American crocodiles are less dangerous to us is because they are nocturnal, and hunt at night (4), so during the day they pose little threat.
Crocodiles do not eat like mammals typically do. Mammals chew then swallow but crocodiles tear then swallow. They cannot chew; they just rip the food apart and consume it in chucks (9). Crocodiles have sharp, cone shaped teeth; these are perfect for tearing and grabbing, like our canine teeth (9). But you cannot chew with these teeth, which forces them to swallow whatever they rip off; with sixty six to sixty eight teeth they can take off a big chunk (4). It can take them up to seventy two hours to digest one meal. Their teeth are quickly replaced, because they are easily worn, so like sharks, they have continually growing teeth ready to go to work when an old tooth is lost (9).
Crocodiles have many built in dive features which allow them to be the ultimate shallow water predator. Their eyes, ears, and nostrils are located on top of their head which allows them to keep those sensory organs above water, but the rest of their body can remain completely submerged (1). This is very effective because they can get very close to their prey without being noticed, allowing them to make a surprise attack. They have a flap of skin that can cover their wind pipe in their mouth, which allows the crocodile to remain breathing through its nostrils while its mouth is open under water (1). Crocodiles have also evolved a third eyelid, which is clear, that closes when the crocodile submerges, allowing it to see clearly underwater (1). The crocodile also has a thin flap of skin covering the ear holes so water does not get into its ears (1). All of these things allow the crocodile to effectively find their way and predate in their habitats.
During mating season, the crocodiles, both male and female, will mate with numerous other partners (6). Mating season occurs between April and May (9). Their reproduction is the most advanced of any other reptile (9). The female initiates interaction with the male. She does many displays to try and calm the male, she “must reduce the aggressiveness of the male whose territory she has invaded” (6). At first, the male shows no interest in the female, but she will persist until the male gives in (6). The female will “nuzzle the sides of the male's head and neck until the males starts responding by caressing the female” (6). This will go on until the male gets onto the back of the female, which is when copulation occurs (6).
Nesting occurs from May to June. The female will build either a dugout hole when a dry area can be found above the water line or a mound to keep the eggs above the water (4). A female will return to the same nesting site year after year (10). The female will lay up to fifty eggs and they will incubate for about eighty five days (American Crocodiles). When the eggs are ready to hatch, the mother will sometimes help and break the egg by gently opening the egg with her jaws (3). After birth, both parents may guard the hatchlings even though they are able to feed themselves once they are born. Even with protection, the survival rate is very low for them mainly because of predation from raccoons (1). Raccoons also predate on the eggs before they even hatch (10).
Adult crocodiles maintain burrows which are not too far from their nesting sites. Their burrows are typically into the bank of the water, and can go in three to nine meters (6). The crocodile moves inland, away from their burrows, during colder periods because it is unable to survive in cool waters (1). Usually they will submerge to hide at even the slightest disturbance; it is only when they feel threatened that they will become aggressive (9). Males are very territorial and aggressive whenever something enters its area (1). They will defend their area from threats from other crocodiles or other large animals, so do not try to enter a male crocodile’s territory. Since crocodiles are ectoderms, or cold blooded, they will sunbathe to warm their body; this is also helpful in speeding up their digestion (9). Crocodiles also use their mouth for heat regulation. They will hold their mouth open to cool off or warm up, depending on the air temperature. This allows body regulation because they have many blood vessels near the surface of their mouth (9), so the air can effect the temperature of their blood. The temperature has a large effect on the crocodiles behavior. When too hot or too cold, the crocodile can become completely inactive (9). When it is warm the crocodile’s digestion is fast, when cold it is very slow, and crocodiles can go months without food if their body temperature is low enough (9).
The threats facing the American Crocodile is a short list, but a complex one. Their existence is becoming more endangered every day. This is mostly due to the expanding human population. Humans and crocodiles are in battle for the same land resources (9). Humans prize coastal land, we embank estuaries, drain swamps, and move into the areas native to crocodiles. We also destroy coastal land for aquaculture (4) which is quickly spreading in poor nations and is detrimental to the crocodile’s natural habitat. Encroachment, by humans, onto their land is the largest and most notable threats to crocodiles in modern day. Without large tracts of land, the crocodile has a hard time maintaining a large, healthy breeding population. Human population has fragmented the crocodiles which can be a major concern for healthy breeding. Another major threat to the American Crocodile is poachers, whom hunt the reptile for its hide (8). Before the killing of the American Crocodile became illegal in most countries it inhabits, the commercial use of crocodile hides, which occurred in the middle of the twentieth century, was the major cause for the initial decline in the crocodile’s numbers (5).
Even though the American Crocodile is endangered, and its future is not bright there are steps being taken in attempt to salvage this prehistoric reptile. To try and cut back on poaching, crocodile farming has been started in many countries, such as Cuba and Jamaica (5). But ranching can have a much larger, positive, impact than just supplying legal hides. Some of the crocodiles from ranches are planned to be put into the wild to supplement the natural populations (4). This is very useful especially in areas that have a healthy environment for crocodiles but do not have many wild crocodiles left due to over hunting. All of the countries that the American Crocodile inhabits now have management programs to try to maintain and grow the present populations, except El Salvador and Haiti (5), and only a few of the countries with management legislation have actually enforced their laws. In 1975, the American Crocodile was listed under International Law as endangered, which put strict regulations on international trade of crocodile products (9). The United States is actively working to help ensure the future of crocodiles within our borders. In 1979, the USA placed the American Crocodile on the Endangered Species Act (6), then “the Fish and Wildlife service formulated a recovery plan in 1984 for this species, centering around habitat protection and management, regular population surveys, reduction in mortality (increased education, plus other measures such as road crossing culverts) and the consideration of captive propagation” (4). So far the program seems to be successful because the population is slowly growing, but it does remain very small.
The American Crocodile is an animal that deserves our respect and should be given a fair chance to live into the next hundred million years. This ancient animal has been around much longer than even the most primitive primates. We need to learn to respect the land they inhabit and work to ensure their future, which will help our future be that much more fulfilling.




Cited Resources
1. "American Crocodile." Images of Life on Earth. ARKive. 30 May. 2005 .
2. "American Crocodile." Marine Parks. National Parks Conservation Association. 22 May. 2005 .
3. "American Crocodiles." Our Enviroment. Florida Light and Power Company. 23 May. 2005 .
4. Britton, Adam. "Crocodylus acutus." Crocodilian Species List. Florida Museum of Natural History. 24 May. 2005 .
5. "Crocodylus acutus." Species Accounts. Florida Museum of Natural History. 23 May. 2005 .
6. Montes, Alejandra. "Animal Diversity Web." Crocodylus acutus. University of Michigan Museum of Zoology. 30 May. 2005 .
7. Richards, Paul M.; Mooij, Wolf M.; DeAngelis, Donald L. ŮEvaluating the effect of salinity on a simulated American crocodile (Crocodylus acutus) population with applications to conservation and Everglades restoration.Ó Ecological Modelling, v. 180 issue 2-3, 2004, p. 371-394
8. "Viva Natura." American Crocodile. The World of Mexican Nature. 01 Jun. 2005 .
9. "Your Enviroment and You." American Crocodile. National Enviroment and Planning Aganecy. 30 May. 2005 .
10. Webb, G. J. W. . "The American Crocodile." Crocodylus acutus. ZooFarm de Colombia. 30 May. 2005 .

For Further Info on this Topic, Check out this WWW Site: http://animaldiversity.ummz.umich.edu/site/accounts/information/Crocodylus_acutus.html.
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