Written by: Mary Sweeters
American crocodiles live in both freshwater and brackish habitats along the coast, including estuaries, lagoons, and mangrove swamps. Some populations have been found in surprising locations, including the cooling canals outside of the Turkey Point nuclear power plant in Florida and in the landlocked, salty lake waters of Lago Enriquillo in the Dominican Republic. Those that live in hypersaline habitats osmoregulate (maintain bodily fresh water content) by drinking available fresh water. Adult American crocodiles eat primarily at night, feeding on various aquatic species including fish (especially mullet), crabs, turtles, and sometimes birds and small mammals. Juveniles eat marine invertebrates and small fish. As predators, crocs play a vital role in the food cycles of their ecosystems. After feeding, the waste they produce fertilizes the aquatic plants growing in the local waterways. These plants are then eaten by herbivorous fish and other aquatic animals, which are then eaten by carnivorous fish that are often prey to the crocodiles.
American crocodiles create distinctive and often complex burrows. These may have more than one entrance, either above the surface or subterranean. Burrows provide protection from predators and offer cool, moist respite when the water table declines to a potentially dangerous low level.
Nesting sites are usually wooded areas near small beaches or along narrow coastal creeks. Nests are made from well draining holes in the ground; if a desirable site is not in close range, crocodiles will build mounds in which to nest. For this reason, crocs lay eggs in the dry season. Females lay between 30 and 60 eggs which hatch after about 90 days, generally at the onset of the rainy season. At the time of hatching, the mother has been observed to open the nest, unearth the eggs and even help the offspring out of their eggs by gently cracking the shells in her mouth. She may then take them to the water in her mouth as well. There have been varying reports of the level of parenting that occurs once the eggs have hatched. With the exception of observed populations in Mexico, the juveniles generally leave the nesting area a few days after hatching and little parental care occurs from this point onward. Hatchling survival estimates are about a one in four chance of reaching age four. Because nests are sometimes well below the surface in areas already close to water, flooding is a factor in mortality. In addition, hatchlings are prey to various animals including raptors, mammals including raccoons and wild cats, and some larger fish.
In areas where human and crocodile populations live in close proximity, crocodiles are often blamed for preying upon domestic animals and occasional attacks on humans. This often overshadows the effect that humans have had on crocodile populations. From the 1930s to the 1960s, American crocodiles were heavily hunted for their skins, decreasing their numbers significantly. Currently, the crocs are hunted on a smaller scale in such areas as Nicaragua, where they are killed illegally during caiman hunting season. One of the most serious factors affecting their survival, however, is land development and habitat destruction. In Ecuador, for example, mangrove swamp destruction for the sake of aquaculture is decreasing habitat space. In Florida, mangroves are also being destroyed to make way for housing and commercial development. With this increasing urbanization, direct human disturbance, including accidental killings in fishing nets and on highways, is playing a factor in crocodile deaths.
While adequate survey data are available primarily in the US, there are current studies underway in other countries to obtain accurate counts of crocodile populations. The American crocodile is an endangered species in the US and is considered threatened in most of the other countries in which it is found. Conservation efforts, including crocodile farming, are in effect in some countries and may be expanded to others. Legal protection has been established in most countries, but unfortunately, enforcement is often inadequate. Education, continued research on threats to the species and expanded conservation efforts are needed to ensure the continued survival of the species.
Alderton, David. Crocodiles and Alligators of the World. Blandford Publishing, London, UK. 1991. pp. 145-151.
Crocodile Specialist Group. Florida Museum of Natural History, Gainesville, FL www.flmnh.ufl.edu/natsci/herpetology/crocs.htm
Crocodilians: Natural History and Conservation. Site hosted by the Crocodile Specialist Group. Created by Adam Britton 1995-2005. www.flmnh.ufl.edu/cnhc/
U.S. Fish and Wildlife Service, Division of Endangered Species. Species account : Crocodylus acutus. http://endangered.fws.gov/i/c/sac0u.html