The American Crocodile (Crocodiles acutus) Crocodylus acutus, or more commonlyreferred to as the American crocodile, “…is the second most widelydistributed of the New World crocodiles, ranging from the southern tip ofFlorida, both the Atlantic and Pacific Coasts of Southern Mexico, as well as theCaribbean islands of Cuba, Jamaica, and Hispaniola” (1 Species).
Theseareas provide the perfect climate for these endangered species that have roamedthe earth for over 200 million years. Florida is known for its large populationof American alligators, which are often confused for the rare Americancrocodile. However, there are vast differences between the two species. Huntedfor their hides and the changing of their habitat to beach front property isslowly pushing the American crocodile out of Florida, the only place it is foundin the United States. “For 190 million years before the first humansevolved, huge populations of crocodilians, in more or less their present form,inhabited the waters and shorelines of rivers, lakes, swamps, and estuaries oftropical and subtropical lands.
Today they represent the last true survivors ofthe huge reptiles that once dominated the seas and landmasses of Earth for over200 million years” (6 Levy). However, “..
.It is inappropriate to treatcrocodilians as living fossils whose inferiority forced them into a marginalecological role as amphibious predators in a world now dominated by mammals. Infact, they are highly specialized for their particular mode of life and haveundergone considerable changes during their long evolutionary history.
..”(14 Ross). “Among living vertebrates, crocodilians are most closely relatedto birds rather than to lizards” (14). Even though these two groups are nowadapted 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 inswimming. The snout is also elongated, with the nostrils set to the end to allowbreathing while most of the body remains submerged under water”. “Thesuccess of the Crocodile is evidenced by the relatively few changes that haveoccurred since crocodilians first appeared about 200 million years ago”.The Crocodile belongs to the family Crocodylinae, which consists of thoseorganisms sharing common crocodilian traits. This Family is further divided intothree subfamilies: Alligatorinae (alligators), Gavialinae (gharial), andCrocodylinae (crocodiles). Very often the American alligator (Alligatorinaemississippiensis) is confused for an American crocodile, even though these twospecies are of the same family they are different in many ways. The alligatorhas a much broader snout and the crocodile a much narrower snout-“..
.narrower snouts usually indicating fish eating-species”. Anothercharacteristic seen in the American crocodile and not the alligator is the fronttwo teeth that penetrate the upper jaw from below as they grow. These teeth areone of the major differences between crocodiles and alligators. A not sorecognizable difference between the American crocodile and alligator is thecrocodile’s ability to regulate saltwater balance in their body. Crocodilesmaintain salt concentrations in their body fluid at the typical level of othervertebrates, which is about one-third that of seawater. “The osmoregulatoryproblems posed by life in fresh or saline waters are related to the amounts ofwater and salts exchanged across various body surfaces. Loss of salts and wateroccurs in feces and urine, through respiration, excretion from salt glands inthe tongue, and through the skin.
The ability of the American crocodile totolerate salt water is related to their low rate of water loss, low rate ofsodium uptake, the ability to excrete excess sodium, and their ability toosmoregulate regularly behaviorally by not drinking saline water or by seekingfresh water after feeding in saline areas”. The American crocodiles willnot drink seawater even when they are dehydrated and the American alligatorwill. However, the alligator does not have the ability to excrete excesssodium. While the American Crocodile is able to regulate its salinity it is notable to maintain a constant body temperature. Crocodiles, like all reptiles, arecold blooded or pokilothermic. “Crocodiles utilize a complex series ofphysiological and behavioral mechanisms to maintain an even body temperature.When their body temperature drops, they use solar radiation to heat their bodiesas they emerge from the water to bask in shallow waters or on the shoreline.
Astheir temperature rises they hold their mouths agape to allow some evaporativecooling. The membranes of the mouth cavity play a major role in regulatingtemperature.” Sometimes crocodiles will partially bask in the sun withtheir tail or head in the water, this allows them to optimally adjust theirtemperatures.
Body temperature can also be adjusted by shunting blood towards oraway from their surface. “As crocodiles cool the superficial blood vesselsconstrict, thereby limiting the amount of heat loss at the animal’s surface andmaintaining a steady core temperature”. Another temperature-regulatingstrategy is mud bathing, which provides another layer of insulation againstextremes in environmental temperatures. The American crocodile is found insubtropical to tropical area, were it is optimal for body temperatureregulation. It is considered an estuarine species that is capable of migratingthrough salt water.
“It is quite the sea going species ranging from Equadoralong the Pacific Coast to western Mexico, and from eastern Mexico to Guatemala,the coastal areas of Colombia and Venezuela, and north through the Caribbean tothe southernmost tip of Florida” (40 Guggisberg). “This species is thecommon resident of coastal habitats, large rivers, and lakes within itsrange” (65 Ross). “Populations are known from freshwater areas locatedwell inland, including a number of reservoirs” (1 Species). “InFlorida, C. acutus can be found in mangrove swamps and saltwater marshes withsandy, undisturbed high spots” (10B Sun-sentinel). “South Florida isthe northern end of C. acutus’s range. Historically, crocodiles have lived inFlorida 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 alwayslived in the extreme southern end of the peninsula. Because of destruction ofhabitat, the crocodiles’ range is now limited to the undeveloped areas from CapeSable to North Key Largo and Turkey Point” (6H Weinlaub). The Americancrocodile was placed on the endangered species list in 1975. “C.
acutus}produces a commercially valuable hide and the principal reason for past declinesin population size can be attributed to the extensive commercialoverexploitation that occurred from the 1930s into the 1960’s (1 Species).”In most populations C. acutus is extensively hunted with only one or twopopulations being adequately protected in national parks in Costa Rica,Venezuela, and the United States” (226 Ross).
“Once crocodilian skinwas a source of high-quality, pliable, decorative leather that takes on a brightsheen when processed, trafficking in skins became big business with hugereturns. Crocodilian skins are processed into a large variety of very expensiveleather products. In the early 1900s US tanneries alone were processing between250,000 and 500,000 skins per year. As supplies dwindled (crocodiles), pricesrose and so did the profitability of hunting. Even after protective laws wereenacted, the profit incentive encouraged large-scale poaching and smuggling ofillegal skins by middlemen servicing the tanneries and leather markets. By themiddle of the 1960s crocodile hunting had left many species criticallythreatened, including the American crocodile near to extinction. Today the worldmarket for crocodilian skins is about 2 million hides per year. Some of thesecome from licensed, controlled hunting and some are harvested from the captivepopulations on farms and ranches.
These skins are considered to be illegal, butat least a million of the hides taken annually are obtained from poachers.”(102 Levy). Also, Habitat destruction is responsible for reduction, and ininhabited area motor vehicles are a major killer of crocodiles. The Americancrocodile almost disappeared from its only habitat in the United States, by the1970s. But now, A well-protected population of crocodiles exists at thesouthernmost tip of Florida. The transformed natural landscape that limitedtheir range now supports about 500 animals. Habitats have been protected by bothstate and federal agencies as well as by the nuclear power industry.
The majornuclear power plant of South Florida at Turkey Point has found increasingnumbers of the endangered crocodiles in residence and even successfully breedingin the 168 mile network of mangrove-lined cooling canals . “At firstenvironmentalists challenged the nuclear power plant at Turkey Point, becausethe heated water, that is a byproduct of the plant, seemed sure to killseagrasses in Biscayne Bay. The Power company’s solution: an extensive networkof cooling canals where the water would be cooled before it was returned toBiscayne Bay. As the canals were dug, the extra sand was piled alongside,fashioning a perfect place for a crocodile to nest” (1A McClure). TheFlorida Power and Light Company has spent hundreds of thousands of dollars incrocodile research efforts and has abandoned plans for expansion of the powerplant, leaving the crocodile habitat safe for the foreseeable future (120Levy). “Once chased by development into a 20-square mile patch of southernDade County and the northern Florida Keys, crocodiles now are reproducing enoughthat they are spreading out again. The generally secretive reptiles are showingup along much of South Florida’s coast, from Sanibel Island to the Bonnet Housein Ft.
Lauderdale”. It is the explosion of suitable nesting sites that isdriving the crocodile’s recovery, which saw an estimated 20 nests in 1974 climbto at least 42 in 1995 (1A). “Nesting is the most reliable way to tell ifcrocodiles are re-colonizing an area, so a clutch of eggs discovered on SanibelIsland in 1995 was particularly encouraging for researchers, even though noneof the eggs were hatched” (1A). “In 1993 there was a record year atTurkey Point, with 12 nests and 155 hatchlings found. And, in 1994 nine nestsand 153 hatchlings were recorded a month into hatching time”. “Thecrocodiles lay their eggs on land in exposed sites, usually within 30 feet ofthe water…
Mound nests are composed of sand and earth combined with a greatdeal of plant material (grasses, water reeds, and leaves), the decay of whichreleases heat to help insulate the eggs. “The hole is excavated with thehind feet, and the excavated soil is subfrequently used to cover the eggs.Mostly as a mound-nesting species the crocodile will first gather a collectionof leaves, grasses, reeds and other plant litter at the selected nesting siteand 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, sheexcavates 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 amajor determination of hatchling sex, this is referred to astemperature-dependent sex determination or TSD.
TSD has been proven in fivespecies of crocodiles and is probably true for all species, because crocodilianslack sex chromosomes. Exclusively females are produced at low incubationtemperatures, males are produced at intermediate temperatures, and hightemperatures produce mostly or only females. Where the female builds her nestand when she lays her eggs both have major effects on the sex ratio for heroffspring. Thermal cues probably play a major role in nest-site selection andconstruction.
It is not surprising that, in many crocodilian nests, all of thesiblings are of the same sex. The crucial period of thermal sensitivity beginsearly in development and extends throughout the first half of incubation”(120 Ross). “Without knowing it FPL created ideal nesting sites forcrocodiles” (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, sustainableutilization programs based on ranching and farming are feasible, However, thedevelopment of management programs based on sustainable utilization must beapproached on a country-by-country basis and be directly linked to the health ofwild populations. A majority of countries 8 of the 17 that the crocodileinhibits have management programs based on complete protection, but only a fewhave enforced legislation. El Salvador and Haiti have no management programswhatsoever.
In five countries, farming of the American crocodile has begun”(3 Species). “In the early 1960s, the wild crocodilian resource necessaryfor 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 wasat this time that farsighted conservationists and skin producers started toinvestigate the feasibility of farming and ranching crocodilians on a sustained,commercial basis. Conservation and educational farms aim at breeding endangeredspecies, such as the American crocodile, in captivity for possible release backinto protected areas in the wild. Commercial development and international tradein endangered species such as crocodiles must satisfy the criteria of theconvention on International Trade in Endangered Species of Fauna and Flora(CITES). Commercial farms must be able to demonstrate, for a defined geographicarea, that the impact of harvesting is not detrimental to the survival of thespecies”. Current efforts are being made to preserve the habitat of theAmerican crocodile (Crocodylus acutus), whose relatives date back as far as 200million years. The American crocodile, “.
..is the second most widelydistributed of the New World crocodiles, ranging from the southern tip ofFlorida, both the Atlantic and Pacific Coasts of Southern Mexico, as well as theCaribbean islands of Cuba, Jamaica, and Hispaniola” (1 Species). TheAmerican crocodile is often confused for its cousin the American alligator themore aggressive and dominant reptile of Florida.
However, there are vastdifferences between the two species. Hunted for their hides and the changing oftheir habitat to beach front property is slowly pushing the American crocodileout of Florida, the only place it is found in the United States. Perhaps withthe continued efforts of FPL and CITES the American crocodile will become a moreabundant species.