Caiman, black

Melanosuchus niger

phylum: Chordata

class: Reptilia

order: Crocodylia

family: Alligatoridae

status: Lower risk, conservation dependent, IUCN Endangered, ESA

range: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Venezuela

Description and biology

The black caiman is the largest species of crocodile in the Western Hemisphere. While an average adult measures 13 to 15 feet (4 to 4.6 meters) long, some black caimans have been known to exceed 20 feet (6 meters). A mature black caiman is black with lighter brown blotches on its head. A young caiman has spots of yellow, green, or white on its head, and its underside is pale. The crocodile eats a variety of small animals (especially rodents) and fish (particularly catfish and piranha). It also preys on small deer, cattle, and other caiman.

Many aspects of the black caiman's reproductive habits are unknown. What is known is that the breeding season varies from September to January, depending on geographic location. Hatching takes place from November to March. A

female black caiman builds a mound nest out of leaves, twigs, and other plant debris. This mound often measures 5 feet (1.5 meters) wide and 2.6 feet (0.8 meter) high. The female then lays a clutch of 30 to 60 hard-shelled eggs into the nest and covers them. As the plant matter decays, the temperature inside the nest rises, causing the eggs to incubate (develop). They hatch after 5 to 6 weeks.

Habitat and current distribution

The black caiman is found throughout the Amazon Basin (area drained by the Amazon River). The largest known concentration of caimans—as many as 1,000—used to be in French Guiana, but uncontrolled hunting has reduced that population. Biologists (people who study living organisms) are unsure of the total number of existing black caimans.

Black caimans prefer to inhabit freshwater ecosystems (living things and their environment). In particular, they seek out undisturbed backwaters, or bends in lagoons and large rivers. They are also found in flooded forest and grassland areas.

History and conservation measures

The black caiman once existed in great numbers throughout the entire Amazonian region. Hunting for its hide has been the major reason for its decline. The crocodile's large size made it an easy target for hunters, who killed millions of black caimans for the leather industry. Serious hunting began in the 1940s and continued until the early 1970s, when the demand for alligator leather decreased and hunters could no longer make a profit. However, poaching (illegal hunting) of the crocodile continues in some areas.

The black caiman is also threatened by habitat loss. Large areas in its range have been cleared by loggers or converted into farms or cattle ranches. Considering the caiman a threat to livestock, many ranchers have killed the animal.

The decline of the black caiman has had a dramatic impact on the region's ecology. One of the animals the caiman preys on is the capybara, the largest member of the rodent family. As the caiman population has decreased, the capybara population has increased. These rodents have caused considerable damage to crops in certain areas of Bolivia and Brazil. The piranha population has also increased because of a decline in the number of caiman. As a result, many cattle have been attacked and killed as they have tried to cross flooded grasslands.

Even a decline in the amount of black caiman excrement (waste matter) has thrown the region's ecology out of balance. This excrement is an important part of the food chain, particularly for zooplankton (microscopic aquatic animals) and phytoplankton (microscopic aquatic plants). Each is an important part of the diet of fish hatchlings. Consequently, the decreasing number of black caiman has resulted in a decreasing number of some fish species.

The black caiman is legally protected in most of the countries in which it is found, but the laws are poorly enforced. Important protected areas for the caiman include the Manu National Park in Peru and the Parque Nacional de Amazonia in Brazil. A program to breed black caimans in captivity and then release them into the wild was established in Bolivia. Some of these programs have clearly paid off. In several different areas the black caiman population increased significantly during the 1990s. In 1999, the International Union for the Conservation of Nature and Natural Resources (IUCN) concluded that the species was no longer threatened with extinction and upgraded its status from endangered to lower risk.