Essay, Research Paper: Alligator


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The American Crocodile (Crocodiles acutus) Crocodylus acutus, or more commonly
referred to as the American crocodile, "…is the second most widely
distributed of the New World crocodiles, ranging from the southern tip of
Florida, both the Atlantic and Pacific Coasts of Southern Mexico, as well as the
Caribbean islands of Cuba, Jamaica, and Hispaniola" (1 Species). These
areas provide the perfect climate for these endangered species that have roamed
the earth for over 200 million years. Florida is known for its large population
of American alligators, which are often confused for the rare American
crocodile. However, there are vast differences between the two species. Hunted
for their hides and the changing of their habitat to beach front property is
slowly pushing the American crocodile out of Florida, the only place it is found
in the United States. "For 190 million years before the first humans
evolved, huge populations of crocodilians, in more or less their present form,
inhabited the waters and shorelines of rivers, lakes, swamps, and estuaries of
tropical and subtropical lands. Today they represent the last true survivors of
the huge reptiles that once dominated the seas and landmasses of Earth for over
200 million years" (6 Levy). However, "…It is inappropriate to treat
crocodilians as living fossils whose inferiority forced them into a marginal
ecological role as amphibious predators in a world now dominated by mammals. In
fact, they are highly specialized for their particular mode of life and have
undergone considerable changes during their long evolutionary history…"
(14 Ross). "Among living vertebrates, crocodilians are most closely related
to birds rather than to lizards" (14). Even though these two groups are now
adapted to different modes of life, they both have an elongate outer ear canal,
a muscular gizzard, and complete separation of the ventricles of the heart.
"Crocodilians are the most advanced of all reptiles. They are elongated,
armored, and lizard-like, with a muscular, laterally shaped tail used in
swimming. The snout is also elongated, with the nostrils set to the end to allow
breathing while most of the body remains submerged under water". "The
success of the Crocodile is evidenced by the relatively few changes that have
occurred since crocodilians first appeared about 200 million years ago".
The Crocodile belongs to the family Crocodylinae, which consists of those
organisms sharing common crocodilian traits. This Family is further divided into
three subfamilies: Alligatorinae (alligators), Gavialinae (gharial), and
Crocodylinae (crocodiles). Very often the American alligator (Alligatorinae
mississippiensis) is confused for an American crocodile, even though these two
species are of the same family they are different in many ways. The alligator
has a much broader snout and the crocodile a much narrower snout-
"…narrower snouts usually indicating fish eating-species". Another
characteristic seen in the American crocodile and not the alligator is the front
two teeth that penetrate the upper jaw from below as they grow. These teeth are
one of the major differences between crocodiles and alligators. A not so
recognizable difference between the American crocodile and alligator is the
crocodile's ability to regulate saltwater balance in their body. Crocodiles
maintain salt concentrations in their body fluid at the typical level of other
vertebrates, which is about one-third that of seawater. "The osmoregulatory
problems posed by life in fresh or saline waters are related to the amounts of
water and salts exchanged across various body surfaces. Loss of salts and water
occurs in feces and urine, through respiration, excretion from salt glands in
the tongue, and through the skin. The ability of the American crocodile to
tolerate salt water is related to their low rate of water loss, low rate of
sodium uptake, the ability to excrete excess sodium, and their ability to
osmoregulate regularly behaviorally by not drinking saline water or by seeking
fresh water after feeding in saline areas". [The American crocodiles will
not drink seawater even when they are dehydrated and the American alligator
will. However, the alligator does not have the ability to excrete excess
sodium]. While the American Crocodile is able to regulate its salinity it is not
able to maintain a constant body temperature. Crocodiles, like all reptiles, are
cold blooded or pokilothermic. "Crocodiles utilize a complex series of
physiological and behavioral mechanisms to maintain an even body temperature.
When their body temperature drops, they use solar radiation to heat their bodies
as they emerge from the water to bask in shallow waters or on the shoreline. As
their temperature rises they hold their mouths agape to allow some evaporative
cooling. The membranes of the mouth cavity play a major role in regulating
temperature." Sometimes crocodiles will partially bask in the sun with
their tail or head in the water, this allows them to optimally adjust their
temperatures. Body temperature can also be adjusted by shunting blood towards or
away from their surface. "As crocodiles cool the superficial blood vessels
constrict, thereby limiting the amount of heat loss at the animal's surface and
maintaining a steady core temperature". [Another temperature-regulating
strategy is mud bathing, which provides another layer of insulation against
extremes in environmental temperatures]. The American crocodile is found in
subtropical to tropical area, were it is optimal for body temperature
regulation. It is considered an estuarine species that is capable of migrating
through salt water. "It is quite the sea going species ranging from Equador
along the Pacific Coast to western Mexico, and from eastern Mexico to Guatemala,
the coastal areas of Colombia and Venezuela, and north through the Caribbean to
the southernmost tip of Florida" (40 Guggisberg). "This species is the
common resident of coastal habitats, large rivers, and lakes within its
range" (65 Ross). "Populations are known from freshwater areas located
well inland, including a number of reservoirs" (1 Species). "In
Florida, C. acutus can be found in mangrove swamps and saltwater marshes with
sandy, undisturbed high spots" (10B Sun-sentinel). "South Florida is
the northern end of [C. acutus's] range. Historically, crocodiles have lived in
Florida from Cape Sable to Lake Worth in Palm Beach County, and fewer numbers,
up to Sanibel on the west coast. The largest population in Florida has always
lived in the extreme southern end of the peninsula. Because of destruction of
habitat, the crocodiles' range is now limited to the undeveloped areas from Cape
Sable to North Key Largo and Turkey Point" (6H Weinlaub). The American
crocodile was placed on the endangered species list in 1975. "[C. acutus}
produces a commercially valuable hide and the principal reason for past declines
in population size can be attributed to the extensive commercial
overexploitation that occurred from the 1930s into the 1960's (1 Species).
"In most populations C. acutus is extensively hunted with only one or two
populations being adequately protected in national parks in Costa Rica,
Venezuela, and the United States" (226 Ross). "Once crocodilian skin
was a source of high-quality, pliable, decorative leather that takes on a bright
sheen when processed, trafficking in skins became big business with huge
returns. Crocodilian skins are processed into a large variety of very expensive
leather products. In the early 1900s US tanneries alone were processing between
250,000 and 500,000 skins per year. As supplies dwindled (crocodiles), prices
rose and so did the profitability of hunting. Even after protective laws were
enacted, the profit incentive encouraged large-scale poaching and smuggling of
illegal skins by middlemen servicing the tanneries and leather markets. By the
middle of the 1960s crocodile hunting had left many species critically
threatened, including the American crocodile near to extinction. Today the world
market for crocodilian skins is about 2 million hides per year. Some of these
come from licensed, controlled hunting and some are harvested from the captive
populations on farms and ranches. These skins are considered to be illegal, but
at least a million of the hides taken annually are obtained from poachers."
(102 Levy). Also, Habitat destruction is responsible for reduction, and in
inhabited area motor vehicles are a major killer of crocodiles. [The American
crocodile almost disappeared from its only habitat in the United States, by the
1970s. But now, A well-protected population of crocodiles exists at the
southernmost tip of Florida. The transformed natural landscape that limited
their range now supports about 500 animals. Habitats have been protected by both
state and federal agencies as well as by the nuclear power industry. The major
nuclear power plant of South Florida at Turkey Point has found increasing
numbers of the endangered crocodiles in residence and even successfully breeding
in the 168 mile network of mangrove-lined cooling canals] . "At first
environmentalists challenged the nuclear power plant at Turkey Point, because
the heated water, that is a byproduct of the plant, seemed sure to kill
seagrasses in Biscayne Bay. The Power company's solution: an extensive network
of cooling canals where the water would be cooled before it was returned to
Biscayne Bay. As the canals were dug, the extra sand was piled alongside,
fashioning a perfect place for a crocodile to nest" (1A McClure). [The
Florida Power and Light Company has spent hundreds of thousands of dollars in
crocodile research efforts and has abandoned plans for expansion of the power
plant, leaving the crocodile habitat safe for the foreseeable future] (120
Levy). "Once chased by development into a 20-square mile patch of southern
Dade County and the northern Florida Keys, crocodiles now are reproducing enough
that they are spreading out again. The generally secretive reptiles are showing
up along much of South Florida's coast, from Sanibel Island to the Bonnet House
in Ft. Lauderdale". [It is the explosion of suitable nesting sites that is
driving the crocodile's recovery, which saw an estimated 20 nests in 1974 climb
to at least 42 in 1995] (1A). "Nesting is the most reliable way to tell if
crocodiles are re-colonizing an area, so a clutch of eggs discovered on Sanibel
Island [in 1995] was particularly encouraging for researchers, even though none
of the eggs were hatched" (1A). "In [1993] there was a record year at
Turkey Point, with 12 nests and 155 hatchlings found. And, in [1994] nine nests
and 153 hatchlings were recorded a month into hatching time". "The
crocodiles lay their eggs on land in exposed sites, usually within 30 feet of
the water… Mound nests are composed of sand and earth combined with a great
deal of plant material (grasses, water reeds, and leaves), the decay of which
releases heat to help insulate the eggs. "The hole is excavated with the
hind feet, and the excavated soil is subfrequently used to cover the eggs.
Mostly as a mound-nesting species the crocodile will first gather a collection
of leaves, grasses, reeds and other plant litter at the selected nesting site
and then create a mound using this plant material combined with earth or sand.
Then the mother compacts all the material into a firm, solid mound. Finally, she
excavates a cavity up to two feet deep, lays her eggs and covers them up.
"In crocodilians, the temperature experienced by the embryo in its egg is a
major determination of hatchling sex, this is referred to as
temperature-dependent sex determination or TSD. TSD has been proven in five
species of crocodiles and is probably true for all species, because crocodilians
lack sex chromosomes. Exclusively females are produced at low incubation
temperatures, males are produced at intermediate temperatures, and high
temperatures produce mostly or only females. Where the female builds her nest
and when she lays her eggs both have major effects on the sex ratio for her
offspring. Thermal cues probably play a major role in nest-site selection and
construction. It is not surprising that, in many crocodilian nests, all of the
siblings are of the same sex. The crucial period of thermal sensitivity begins
early in development and extends throughout the first half of incubation"
(120 Ross). "Without knowing it FPL created ideal nesting sites for
crocodiles" (1E Miller). Along with the cooling canals of Turkey Point,
Everglades National Park, and Key Largo are the key breeding areas for C. acutus.
"As American crocodiles produce commercially valuable hide, sustainable
utilization programs based on ranching and farming are feasible, However, the
development of management programs based on sustainable utilization must be
approached on a country-by-country basis and be directly linked to the health of
wild populations. A majority of countries [8 of the 17] that the crocodile
inhibits have management programs based on complete protection, but only a few
have enforced legislation. El Salvador and Haiti have no management programs
whatsoever. In five countries, farming of the American crocodile has begun"
(3 Species). "In the early 1960s, the wild crocodilian resource necessary
for the skin trade had dwindled and the first conservation laws were enacted,
resulting in a simultaneous rise in prices and in the demand for skins. It was
at this time that farsighted conservationists and skin producers started to
investigate the feasibility of farming and ranching crocodilians on a sustained,
commercial basis. Conservation and educational farms aim at breeding endangered
species, such as the American crocodile, in captivity for possible release back
into protected areas in the wild. Commercial development and international trade
in endangered species such as crocodiles must satisfy the criteria of the
convention on International Trade in Endangered Species of Fauna and Flora
(CITES). Commercial farms must be able to demonstrate, for a defined geographic
area, that the impact of harvesting is not detrimental to the survival of the
species". Current efforts are being made to preserve the habitat of the
American crocodile (Crocodylus acutus), whose relatives date back as far as 200
million years. The American crocodile, "…is the second most widely
distributed of the New World crocodiles, ranging from the southern tip of
Florida, both the Atlantic and Pacific Coasts of Southern Mexico, as well as the
Caribbean islands of Cuba, Jamaica, and Hispaniola" (1 Species). The
American crocodile is often confused for its cousin the American alligator the
more aggressive and dominant reptile of Florida. However, there are vast
differences between the two species. Hunted for their hides and the changing of
their habitat to beach front property is slowly pushing the American crocodile
out of Florida, the only place it is found in the United States. Perhaps with
the continued efforts of FPL and CITES the American crocodile will become a more
abundant species.
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