American crocodile
In 1875, William Temple Hornaday and C. E. Jackson traveled to Florida to collect alligator hides. Word reached them of a "big old gator" living in Arch Creek, at the head of Biscayne Bay. Hornaday and his companions went looking for it. After a few hours they spotted the animal on the bank, sprawled in a saw-grass wallow. Hornaday called it "a perfect whale of a saurian," gray and enormous. It was not an alligator at all. It was a crocodile, and it belonged to the species this documentary follows: the American crocodile, Crocodylus acutus. A crocodilian of the Neotropics, it is the most widespread of the four crocodile species native to the Americas. That mix-up raises questions. Why was a reptile this large mistaken for an alligator? What lets it survive in salt water? Where did its family come from, how does it raise its young, and what happened to it once people took an interest?
Georges Cuvier described the species in 1807 and gave it the common name "sharp-snout alligator." In 1822, Constantine Samuel Rafinesque proposed that it was really a crocodile. Hornaday's redescription of the animal as Crocodylus floridanus did not hold. That name is now treated as an invalid junior synonym of Crocodylus acutus.
The naming puzzles continue today. Genetic assays suggest that Jamaican American crocodiles may differ from the Cuban crocodiles living beside them, despite a significant history of hybridization. Comparisons across the Caribbean hint that the island populations of Cozumel and Banco Chinchorro could even be genetically distinct species. Populations in Florida, Jamaica and Hispaniola also differ in their gene frequencies.
Until 2020, the evolution of the species was poorly understood. Then researchers described Crocodylus checchiai, a species from the Miocene. It indicates that the American crocodile, the Orinoco crocodile, Morelet's crocodile and the Cuban crocodile all share an African ancestor. The find may even sit at the base of the whole radiation, a missing link between African and American crocodiles.
The genus Crocodylus likely arose in Africa and spread toward Southeast Asia and the Americas. An origin in Australia or Asia has also been considered. Phylogenetic evidence points to a split from its closest recent relative, the extinct Voay of Madagascar. That split happened around 25 million years ago, near the boundary between the Oligocene and the Miocene.
The only confirmed fossil of an American crocodile comes from the Río Tomayate locality in El Salvador. It dates to the Early or Middle Pleistocene.
Beneath the tongue of a crocodile sit salt glands, and several species use them to tolerate seawater. Only two, the saltwater crocodile and the American crocodile, commonly thrive in it. That ability explains the animal's map. It has colonized many Caribbean islands and some Pacific coastal ones. Its range runs from southern Florida and the coasts of Mexico down to Peru, Ecuador, Colombia and Venezuela. Margarita Island and Martinique are part of it, as are Cuba, Jamaica and Hispaniola.
Mangrove swamps, river mouths, lagoons and brackish lakes all make good homes. Individuals have even been found at sea. On many Caribbean cays and islets with no fresh water at all, they live on the beaches. They also inhabit lakes saltier than the ocean. Costa Rica is especially rich in them.
Two Caribbean islands fall outside the range. On Puerto Rico and Isla de la Juventud, the introduced spectacled caiman has taken the crocodile's place.
Lago Enriquillo, a hypersaline lake in the Dominican Republic, holds the largest population in the Caribbean. Hispaniola once held crocodiles throughout the island. Now the only confirmed presence is at that lake and at Etang Saumâtre in Haiti. In Haiti the population is nearing extirpation from overhunting and poaching. Jamaica fares better, with crocodiles in most of its swamps and the brackish stretches of its rivers.
Recent sightings on Grand Cayman lead experts to think crocodiles are swimming over from Cuba and slowly repopulating the island. Trinidad is a different case. Crocodiles reported there are thought to have been moved accidentally, so the island is not considered part of the native range.
A changing climate now brings more hurricanes and cyclones to the Caribbean. Crocodiles there have been reported in poorer body condition. Shifts in salinity, temperature and prey could slow the recovery of these populations.
A newly hatched American crocodile measures about 27 cm and weighs roughly 60 g. Adults in continental rivers range from 2.9 to 4 m, with males weighing up to 382 kg. Females run from 2.5 to 3 m and up to 173 kg. In Florida, adults commonly weigh between 50 and 250 kg and measure 2.5 to 3.85 m. Conservation efforts seem to be producing more large crocodiles there, and some reportedly exceed 4 m.
Eight adults from Costa Rica ranged from 2.82 to 4.83 m. The largest of them weighed about 538 kg. Yet weight varies widely in mature animals. Another Costa Rican specimen, at 3.95 m, was found to weigh 500 kg. As a rough guide, a crocodile of 3 m would weigh around 100 kg, and one of 4 m about 270 kg. A 6.25 m animal would reach around 1100 kg.
A captive male named Papillon measured 4.3 m and weighed 500 kg. He was estimated to be more than 80 years old when he died. The largest recorded female measured 4.4 m and weighed 450 kg. Reports of animals between 6 and 7 m, weighing 900 to 1300 kg, remain unverified estimates.
The body follows the standard crocodilian plan: short stocky legs, a long powerful tail and rows of bony scutes down the back. Yet the American crocodile has the most reduced dorsal osteoderms of any living crocodilian. Scientists can identify individuals by their dorsal scute patterns. A 3.2 m specimen weighing 164 kg once produced a bite force of 4355 N. Its eyes have protective nictitating membranes and lacrimal glands that make tears.
Nostrils, eyes and ears sit high on the head, so the rest of the body can stay hidden underwater. The snout is longer and narrower than an American alligator's, though broader than an Orinoco crocodile's. The skin is paler and grayer than the alligator's. Juveniles carry distinct dark cross-marks that usually fade with age. Morelet's crocodile, a smaller Mexican species, is sometimes confused with this one.
Halfway down the snout, in front of the eyes, rises a distinctive bump. It goes by names such as the medial rostral boss or the median preorbital elevation. The other three American Crocodylus species have it too, though less pronounced. Because the species prefers salty water, its scutes can carry ticks, leeches, barnacles and even sea anemones.
In Haiti, fiddler crabs made up 33.8 percent of the diet by weight for hatchlings and 62.3 percent for juveniles. Aquatic insects, their larvae and snails rank high at that age elsewhere. As crocodiles grow, the snout becomes broader and bulkier, a sign that prey is changing. It is already broader than the snout of specialist fish-eaters such as gharials, which lets the species take a wider menu. Prey runs from insects to full-grown cattle.
One 1.2 m specimen in Mexico had a catfish, a mourning dove and a bare-tailed woolly opossum in its stomach. Florida crocodiles favor mullet, bass, tarpon, large crabs, snakes, opossums and raccoons. In southern Florida they rely on marine food sources 65 percent of the time. Haitian adults eat herons, storks, flamingos, pelicans and other birds, followed by fish, and sometimes catch turtles, dogs and goats. A 3 m adult from Honduras held a 1.5 m crocodile of its own species, a turtle shell and peccary hooves.
On Costa Rican beaches, crocodiles have been recorded killing adult female olive ridley sea turtles that come ashore to nest. Hunting peaks in the first hours after nightfall, especially on moonless nights. The method is the usual crocodilian ambush. A crocodile waits at the water's edge or near the surface, then drags prey under to drown it. On land, larger animals can charge at nearly 10 mph. In water they can reach 20 mph, though they cannot hold that speed. In Mexico, large adults have occasionally become habitual predators of goats, dogs, pigs and cattle, a source of conflict with farmers.
Adults have no natural predators. They prey on lemon sharks, and sharks avoid areas where the crocodiles live. American alligators are usually dominant. Once, a crocodile escaped its cage at a Florida zoo and attacked a large male alligator in the neighboring pen. The crocodile was killed. Yet one confirmed case exists of a wild crocodile preying on a sub-adult alligator in Florida. Habitat partitioning keeps the two apart in most places.
Spectacled caimans fare worse. Where crocodiles are healthy, caimans stay few. Where crocodiles are depleted or gone, caiman numbers grow. In Cuba, the smaller but more aggressive Cuban crocodile dominates the American crocodile. The same happens when the two are kept together in zoos or on crocodile farms. In Mexico, escaped Morelet's crocodiles have formed feral populations that compete with the native animals.
Florida adds a modern danger. Burmese pythons, several other python species, boa constrictors and various anacondas are invasive there, and some growth stages of these snakes may eat American crocodiles.
Late fall and early winter bring the low-frequency bellows of males courting females. Unlike other crocodiles, this species uses acoustic signals to communicate, mostly over short distances during courtship and hatching. Body size matters more than age for breeding, and females reach maturity at about 2.8 m.
In February or March, a gravid female builds a nest from sand, mud and dead vegetation at the water's edge. Well-drained beaches and abandoned canal levees are common sites. Location is critical. With the right amount of vegetation, the eggs develop within a narrow temperature range. Because sex in crocodilians depends on temperature, slight shifts can produce all-male or all-female clutches, which could harm a population.
About a month later she digs a wide hole diagonally into the side of the nest. She lays 30 to 70 eggs in it, depending on her size. The average clutch is 38. Females often reuse the same holes for many years. The white, elongated eggs measure 8 cm by 5 cm.
During the 75- to 80-day incubation, parents guard the nest, often living in a hole in the nearby bank. Females especially defend it ferociously. Still, raiders get through. Raccoons take eggs in Florida, Belize and Costa Rica, and are arguably the worst natural nest predator of crocodilians in the Americas. White-nosed coatis do so in Costa Rica, and foxes, skunks and coyotes in Mexico. American black bears raid nests in southern Florida, and red imported fire ants, crabs and vultures join in. In Panama, green iguanas sometimes dig up eggs, though the mother occasionally catches and eats them.
Hatching tends to coincide with the first summer rains in July and August, before the waters flood. The young call out in soft, grunt-like croaks, and the sounds draw the female to the nest. She uncovers the eggs if needed, helps the hatchlings out and scoops them into her mouth. She then carries them to the nearest water.
Hatchlings may hunt within a few days. A mother can stay attentive to their calls and keep transporting them for weeks. About five weeks after hatching, the young disband. On average only 16 percent reach adulthood. Roadside hawks and laughing falcons in Mexico take some. Barred catfish in Colombia, Atlantic tarpons, common snook and lemon sharks in Florida, and Central American boas in Belize take others. Some young crocodiles even eat each other.
One more oddity appeared in genome sequencing. Females of this species can sometimes reproduce through facultative parthenogenesis, by a mechanism called terminal fusion automixis.
As early as 1829, Rafinesque suspected that Florida held something besides alligators. Confirmation had to wait until 1869, when a specimen was brought back for examination. Records show crocodiles were plentiful at places like Key Largo and Miami Beach, wherever mangroves offered nesting and feeding grounds.
Then came the leather trade. By the end of the 19th century, hunting crocodiles for their hides was a cottage industry in South Florida. In 1910, a railroad to link the mainland with the Keys began massive habitat destruction. Hunters who moved to the upper Keys around that time slaughtered almost every crocodile in northeast Florida Bay for commercial sale. The killing did not end until the 1970s. At one low point that decade, fewer than thirty nests were counted in total.
Today the United States population is estimated at 2,000 and growing. As of 2020, crocodiles seem to be moving south to reclaim former habitat in the Florida Keys, where numbers are multiplying quickly. Old records show they once lived in mangroves as far north as Tampa Bay. Most are found south of Miami, in Everglades National Park, Florida Bay, Biscayne Bay, Dry Tortugas National Park and the Keys. A sizable population lives near Homestead at the Turkey Point Nuclear Generating Station. Some individuals have turned up in Palm Beach, Brevard, Pinellas and Sarasota counties.
Contrary to a popular myth, alligators did not keep crocodiles from the brackish waters farther north. Climate did. Crocodiles tolerate cold poorly. An alligator can survive for a time in water at 7.2 C or colder, but a crocodile in that water would lose consciousness and drown. The southern tip of Florida is therefore the only place on Earth where alligators and crocodiles coexist.
Warmth also explains daytime basking, when crocodiles hold their mouths wide open. This exposes blood vessels in the mouth to cooler or warmer air and helps regulate body temperature. The crocodiles are social only occasionally, gathering to feed and bask.
Salt is a risk too. Crocodiles grow faster than alligators and handle seawater better. Yet those studied in northeast Florida Bay under conditions saltier than seawater survived less, grew more slowly and were in poorer condition. Canal networks in Florida and Biscayne Bays reduce freshwater flow, which makes hypersaline episodes longer and more frequent.
On the 20th of March 2007, the United States Fish and Wildlife Service changed the species from endangered to threatened. It remains protected from poaching and killing under the federal Endangered Species Act. NatureServe rates the Florida population Imperiled. About two-thirds of crocodile deaths in southern Florida come from road collisions. Roughly 10 percent are intentional killings, and only about 5 percent have natural causes. The species also serves as a flagship species and ecological indicator in the Everglades World Heritage Site.
In May 2007, two children were attacked and killed by American crocodiles within a single week. One attack happened in Mexico, just south of Puerto Vallarta, and the other in Costa Rica. Attacks have also been reported in Panama. A study by the IUCN found that this species has the highest incidence of reported attacks among American crocodilians, though deaths are rare. It rates somewhere in the middle of all crocodilians for temperament. Attacks are far fewer than those by the saltwater and Nile crocodiles.
The animal's usual manner is shy. It will not stand its ground, and it flees at the very sight of people. At 02:00 on the 24th of August 2014, a man and a woman were swimming in a canal in Gables by the Sea, a community in Coral Gables, Florida. The canal was known to hold crocodiles. A crocodile bit the man's shoulder and the woman's hand. It measured 12 ft 1 in and weighed an estimated 550 lb. Yet it released them and moved away. This was the first documented wild crocodile attack on humans in Florida since records of such conflict began. In the Cancun area of southeastern Mexico, 36 attacks were reportedly recorded from 1995 to 2017.
The IUCN lists the American crocodile as vulnerable. Hide hunting, pollution, habitat loss and commercial farming have made it endangered in parts of its range. Overhunting in the 1950s and 1960s led Venezuela to ban commercial harvesting of crocodile skins for a decade, starting in 1972. In Jamaica, rampant poaching for meat has caused a significant population drop. The lack of government action has made it worse.
Population data are limited. An estimated 1,000 to 2,000 crocodiles live in Mexico, Central America and South America. A separate estimate puts another 500 to 1,200 in southern Florida. The number of mature individuals as of 2020 is around 5,000.
Updated
Common questions
What is the American crocodile?
The American crocodile (Crocodylus acutus) is a crocodilian found in the Neotropics. It is the most widespread of the four crocodile species native to the Americas.
Where does the American crocodile live?
The American crocodile lives along coasts from southern Florida, Cuba, Jamaica, Hispaniola and Mexico south to Peru, Ecuador, Colombia and Venezuela. It favors mangrove swamps, brackish lakes, lagoons, cays and small islands, and it can also be found at sea.
How big do American crocodiles get?
Adult American crocodiles in continental rivers range from 2.9 to 4 m, with males weighing up to 382 kg. Unverified reports describe animals of 6 to 7 m. A captive male named Papillon measured 4.3 m and weighed 500 kg.
Is the American crocodile dangerous to humans?
The American crocodile is potentially dangerous, but it is shy and usually flees from people. An IUCN study found it has the highest incidence of reported attacks among American crocodilians, though fatalities are rare.
How many American crocodiles are left in the wild?
The number of mature American crocodiles was estimated at around 5,000 as of 2020. The IUCN lists the species as vulnerable. The United States population is estimated at 2,000 and growing.
How do American crocodiles care for their young?
A female American crocodile lays 30 to 70 eggs in a nest hole and guards the nest during a 75- to 80-day incubation. When hatchlings call from inside the eggs, she uncovers them and carries them to water in her mouth. The young disband about five weeks after hatching.
Why do American crocodiles live only in southern Florida in the United States?
Climate limits the American crocodile in the United States, because crocodiles tolerate cold poorly. A crocodile in water at 7.2 C would lose consciousness and drown, while an alligator can survive such water for some time.
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