Alligator
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.