AMERICAN CROCODILE
Crocodylus acutus
Family: Crocodylidea
Order: Crocodila
STATUS: Endangered
DESCRIPTION: The American crocodile is one of two species of crocodilians endemic to the United States. The American crocodile is a large mottled, brownish-gray reptile. The back is covered with several rows of large, keeled scales. The lateral row of scales tends to be irregular with many scales missing or out of line. The neck is lightly armored with areas of exposed skin. The belly is covered with smooth, soft, rectangular whitish scales. The snout of the crocodile is tapered with the fourth tooth of the lower jaw exposed. The tail makes up approximately one-half the total length of the animal. A row of heavy scutes projects dorsolaterally from each side, and converge about midway down the tail. The posterior half of the tail is flattened laterally and capped with a single row of projecting scutes.
Adult crocodiles average 7 to 11 ft. in length, and like all members of the Order Crocodila, males are larger than females. The largest modern specimen measured in Florida was 12 ft. 5 in. long, but a specimen of 15 ft. 6 in. was reported in the late 1800s.
The American crocodile bears a superficial resemblance to the familiar American alligator, although the two species are only distantly related. The crocodile can be distinguished from the alligator by its brown rather than black colored skin. The crocodile has a distinctly longer and narrower snout than the alligator and its fourth tooth protrudes outside the upper jaw. Crocodiles have a conspicuous pore near the posterior margin of each ventral scale. American crocodiles often bask with the mouth held open wide, a behavior rarely seen in alligators.
HABITAT AND DISTRIBUTION: The American crocodile is a tropical species which reaches its northern limit or its distribution in southern Florida. The American crocodile primarily inhabits coastal swamps and rivers. On the Atlantic coast they can be found in extreme southern Florida, in Cuba, Jamaica, Hispaniola, and along the Caribbean coast from Venezuela north to the Yucatan Peninsula. The crocodiles are also found along the Pacific coast from Sinaloa, Mexico, south to the Rio Tumbes in Peru. In Florida it occurs primarily in mangrove swamps, but it occasionally wanders a few miles inland.
In Florida crocodiles historically were found as far north on the Atlantic coast as Lake Worth. Today southern Biscayne Bay appears to be the northern limit, although individual crocodiles occasionally wander further north. On the west coast crocodiles once ranged up to Tampa Bay, but today are found only as far north as Sanibel Island. The recent breeding range of the American crocodile includes the mainland shoreline from southern Biscayne Bay (Turkey Point) west to Cape Sable, as well as North Key Largo and some islands in Florida Bay. On the west coast a breeding population of crocodiles has been identified in Collier County. Information is scarce on crocodile populations from the Ten Thousand Islands to Cape Sable.
LIFE HISTORY AND ECOLOGY: Most crocodilians are opportunistic predators taking whatever they can catch. The Nile crocodile (Crocodylus niloticus) and the Indo-Pacific Estuarine crocodile (Crocodylus porosus) are notorious for taking large prey, including man. However, the American crocodile seldom takes anything larger than a raccoon, rabbit, or cormorant. The typical diet is made up primarily of crabs, fish, snakes, turtles, birds and small mammals. During periods of low ambient temperatures, the crocodile rarely feeds due to slowed metabolism caused by lower body temperature. Contrary to popular belief, the American crocodile is not more aggressive than the American alligator.
Male crocodiles establish and defend breeding territories from late February through March. Vocalization, body posturing and outright aggression are used in defending these territories. The females roam freely through these male defended territories where courtship and mating take place. The American crocodile goes through a very ritualistic mating sequence which is considered to be one of the most structured of all crocodilians. Nesting takes place about a month later in late April or early May. Nests are typically built above the vegetation line on beaches, stream banks, canal berms or road grades. On average between 20 to 50 eggs are deposited which hatch about 86 days later. Hatching success is only considered mediocre.
At hatching time the female must open the nest and carry the young to the water in her mouth. The hatchlings are not able to dig out on their own and will die if not released from the nest. Unlike the alligator, the female crocodile does not remain with her young after they are hatched. The hatchlings are about 10 inches in length and feed primarily on small fish, crabs and insects. Initial growth is rapid, and by four months of age they average about 18 inches in length. There is little or no growth during the cooler winter months, but rapid growth resumes in late March or early April. By the end of the first year young crocodiles average about 25 inches in length.
Females reach sexual maturity at about seven feet in length, a size reached at an age of about 10 to 13 years. It is not known at what age and size the males mature. Similarly, the maximum reproductive age for either sex is not known, although it is known that captively reared crocodiles eventually fail to reproduce.
BASIS OF STATUS CLASSIFICATION: Historic estimates of the numbers of American crocodiles found in South Florida are difficult to substantiate because many records are anecdotal and many early observations were probably confused with the alligator. However, reliable accounts estimate that between 1,000 to 2,000 crocodiles existed in South Florida during the late 19th century and the first half of the 20th century. Many of Florida's crocodiles were collected for museums and live exhibits, but many were also legally hunted for meat and hides. By the mid 1970s, crocodile numbers had been reduced to between 100 to 400 animals.
In addition to the taking of individual crocodiles, habitat destruction and modification has been occurring since the beginning of modern human settlement in South Florida. Habitat loss and fragmentation due to increases in urbanization and agricultural land uses has adversely affected the population. Estuarine habitat from Lake Worth south to Biscayne Bay has been nearly totally destroyed by urbanization, and crocodiles have been essentially extirpated from these areas. Extensive urbanization has eliminated the crocodile from the mid and lower Keys.
Today the crocodile population is estimated between 500 to 1000 animals. Most known successful nesting occurs along the mainland shoreline from Turkey Point to Cape Sable, on Key Largo, or on some of the smaller islands in northeastern Florida Bay. Despite the fact that most of the breeding range in Florida is protected in Everglades National Park, Crocodile Lake National Wildlife Refuge, Key Biscayne National Park, J.N. "Ding" Darling National Wildlife Reserve, Collier-Seminole State Park and at Florida Power and Light's Turkey Point nuclear power plant, the limited distribution of the crocodile makes it susceptible to catastrophic loss through disease or hurricane of both individuals and habitat.
HABITAT GUIDELINES: There are two areas within Collier County where crocodiles are known to nest, Collier-Seminole State Park and the Marco Island Airport. The land within the State Park is protected from any future development, but the land around the airport is open to development. Only through protection of existing breeding areas can the continued existence of the American crocodile be assured.
RECOMMENDATIONS: Given the limited distribution of the American crocodile in Florida, it is critical that no further reduction in habitat be allowed. Within habitats occupied by crocodiles, such activities as swimming, diving, and boating should be discouraged. The American crocodile is a large and potentially dangerous predator. There is a need for a rational and well managed public educational effort to inform people about the status and biology of the crocodile. The survival of this species in Florida will depend upon an informed, enlightened, and tolerant public.
REFERENCES:
Moler, P.E., 1992. American Crocodile. Pages 83 - 89 in P.E.Moler ed. Rare and
endangered biota of Florida, Volume III, amphibians and reptiles. University Press
of Florida; Gainesville, Florida
U.S. Fish and Wildlife Service, 1998. Multi-species recovery plan for the threatened and
endangered species of South Florida, Volume 1 of 2, The Species.Technical/Agency.
Draft. Vero Beach, Florida
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