Creature Feature: The American Crocodile is Florida’s Comeback Kid

The American crocodile looks a lot like an alligator, but it is lighter in color, has a longer and more pointed snout, and has some teeth that remain visible when its mouth is closed. Photo by Moni3 via Wikipedia.

Most Americans are unaware that there are crocodiles, including genuinely huge ones, living in South Florida. Actually, these fascinating creatures have staged a dramatic comeback. It’s a wildlife success story with some interesting twists.

The global inventory of crocodilians includes 23 species. One of them, the American crocodile (Crocodylus acutus), is a New World species found in some areas of Central America, the Caribbean, and South America (Venezuela and Peru). A small population of these crocs also inhabits parts of southern Florida, including Everglades National Park and Biscayne National Park. Its range there overlaps that of the alligator, making this the only place in the world where crocodiles and alligators coexist. The size of Florida’s croc population has been estimated at anywhere between 500 and 2,000 individuals, and it seems that the upper end of that range is a reasonable figure.

While it’s hard to get a count that everyone can agree with –some count hatchlings, for example, while others don’t -- wildlife biologists do agree that Florida’s croc population has been growing at a rapid pace in recent years, rebounding from lows reached more than 50 years ago. By 1960, decades of hide hunting, habitat loss, road kills, gill-net fishing bycatch, nest destruction or flooding, and related problems had pushed the species close to regional extinction. In fact, until quite recently the crocodiles in Florida were in such dire straits that the species was federally-listed as endangered.

The U.S. Fish and Wildlife Service had a recovery plan in place for the American crocodile by 1984. While captive breeding was provided for as an emergency measure, the recovery plan emphasized mortality reduction – using road crossing culverts, for example, to reduce highway mortality – as well as habitat preservation and improvement. These measures worked. In 2007 the USFWS was finally able to downgrade the croc’s status to “threatened” on the evidence of significant recovery. It’s a wildlife success story that many point to with great pride. As some have said, the crocodile is Florida’s “comeback kid.”

Not everybody is happy about that. When people hear the word “crocodile,” many think of a big, aggressive creature that will kill you and eat you if it gets the chance. Florida’s crocs, in other words, tend to be bum-rapped by association with the notorious Nile crocodiles and saltwater crocodiles, which have claimed thousands of human lives in historic times. By contrast, the American crocodile is a shy, reclusive creature with a well-established reputation for avoiding people. Unlike alligators, crocs are rarely seen. And as far as we know, not a single human being has been killed by a crocodile in the United States.

This is not to say that Florida’s crocs won’t kill pets and small livestock, or that the risk to people is zero. Attacks on humans are genuinely rare, but crocs do injure or even kill people now and then in Central America and the Caribbean.

Few American crocs in Florida grow to lengths exceeding about 13 feet, but much greater lengths are possible. The biggest croc documented in Florida is a recently discovered one that wildlife biologists reliably estimated at 16 feet. In that size range, a crocodile must be respected for what it is -- a creature that is likely to regard humans as prey.

What American crocodiles normally eat are fish, turtles, crabs, snails, waterfowl, frogs, insects, raccoons, and other small prey found in or near the water. They’ll eat carcasses, too, if they find them. When food is scarce, as it might be during prolonged dry periods, crocs can go for months without eating.

Like alligators, crocodiles feed primarily at night and are inclined to bask in the sun during the day.

Many people who see crocs in Florida don’t recognize them for what they are. The animals do, after all, resemble alligators more than a little bit. If you look closely, however, you can see that the croc’s snout is longer, thinner, and more pointed (acutus is Latin for "sharp" or "pointed"), and two long teeth (the fourth ones on the bottom jaw) remain visible when its mouth is closed. Crocs are also typically lighter in color, being olive gray or tan grey with darker markings and a white or yellowish-white belly. Length isn’t a reliable indicator, since big gators can grow about the same length as big crocs. (In the unlikely event that you could count teeth, it would be useful to remember that a croc has only 66 to 68, whereas an alligator has 74 to 80.)

Since American crocs can thrive in brackish coastal water as well as freshwater, their range includes not only rivers, lakes, and reservoirs, but also tidal estuaries, coastal lagoons and mangrove swamps. To search out new habitats, they’ll move around in canals and streams, swim well out to sea, and even travel considerable distances overland. These adaptive abilities and dispersing behaviors can cause some problems, as when crocs roam into residential areas, but they can also lead to the colonization of important sanctuaries -- the sheltered cooling water canals of the Turkey Point nuclear power plant and the remote waters of Dry Tortugas National Park (in the Gulf of Mexico 70 miles west of Key West) being two prime examples. This is a very competent species.

It’s a long-lived one too. American crocs can live 50-70 years. And like trees, they never stop growing. A true giant can end up stretching well over 15 feet and weighing more than half a ton.

There are, of course, various constraints on croc numbers. Breeding, nesting and predation issues are three important ones. Female crocs don’t become sexually mature until they are about six to eight feet long, which can take as long as ten years. Nesting is problematic too, since water levels can be unreliable even during the dry season (winter) when nesting occurs. The mating season begins in January and may last into May. Where the habitat permits, female crocs excavate holes above the water line for nests, lay around 40 eggs, and then guard the nests quite attentively. It takes about 60 to 90 days for the eggs to hatch, and a lot can happen in that time. Flooding is a particularly serious hazard. Excessive rain can raise the water level too high, drowning nests and destroying the eggs.

Lacking such calamities, several dozen ten-inch long hatchlings leave the nest (with parental help) about the time that the rains return, and then disperse within a few days. Adult crocs typically guard their hatchlings for a little while, but not in the prolonged, doting way that alligator parents do. Within a year, at least half of the croc hatchlings are likely to end up as food for birds, raccoons, snakes, large fish, crustaceans, and other predators, including larger crocs (which are quite cannibalistic).

Postscript: Back in the early 1970s when Florida Power and Light built the Turkey Point Nuclear Power Plant on Biscayne Bay about 24 miles south of Miami (and near Biscayne National Park), the utility created a cooling system that employs 169 miles of canals with soft berms. You could scarcely have prescribed a better, more protected habitat for crocodiles. Today the crocodile paradise that is Turkey Point has Florida’s largest concentration of crocodiles – around 500 adults – and is the species’ number one nursery grounds. So far, scientists conducting research at Turkey Point have captured, tagged, and released more than 3,000 adult and hatchling crocs.

Comments

What a great article on American Crocs. I especially like the alligator croc comparison. Sans counting the teeth of course, not recommended:)
has anyone looked into there being a relationship between the temperature of the water and the presence and effect on crocs near the power plant? While working in Florida with crocs, I was led to believe the crocs were attracted to the water heated by the power plant. Is this true or was someone pulling my tail?

Very well written! Just one small detail (there's always one)...the 'Australian' croc and the Saltwater croc are one in the same, (Crocodylus porosus).** To answer the question posted by Reptiles Alive; yes, the American crocs are attracted not only to the warm water of Turkey Point, but also to the security of the location. Very few people are allowed into the cooling canals so the animals remain relatively undisturbed.

[** Nice catch. The correction has been made. Ed.]

Thank you for the great article! We learned some interesting facts about crocodiles. My students thank you. ui