As of November 2026, the black caiman is the largest kind of caiman, and it lives in the slow rivers, lakes and flooded land of the Amazon. On floodplain lakes along the Ichilo River in Bolivia, a survey found approximately 1 black caiman per kilometre of shore, against approximately 6 yacare caimans. Both populations consisted mostly of juveniles, and the authors found that the black caiman appeared relatively well protected there. A black caiman has large eyes and a narrow snout, and its dark colour helps it go unnoticed in the water. It also has acute sight and hearing, which help it hunt at night. It can grow longer than 4 metres, and the biggest old males can be longer than 5 metres and weigh more than 400 kilograms.

Black caimans nest annually in the dry season, and in northeastern Ecuador seven black caiman nests were monitored at two lagoons, where nesting matched the low-water season and flooding of the nests was identified as the main cause of egg loss. A black caiman nest is a mound approximately 1.5 metres across, made of earth, leaves and sticks, and sunlight or the heat of rotting plants can warm it. A clutch holds 21 to 75 eggs, each weighing 90 to 155 grams, and the eggs take 60 to 90 days to hatch. A newborn black caiman is approximately 30 centimetres long. Unlike the spectacled caiman, black caiman females usually build their nests near water.

In some areas the spectacled caiman, a smaller caiman, has moved into habitats left open by the decline of black caimans. A study of stomach contents in a Peruvian reserve found that young black caimans eat mostly insects and crustaceans, while larger ones eat fish. Over its life, a black caiman changes from eating small animals without backbones to eating animals with backbones. A scientist not in the study said that similar diets are not proof of competition between two species. A grown black caiman is among the biggest predators in its part of the Amazon, and it may even eat animals as big as a capybara.

Without reliable census information, population surveys are the first step for any management program. People hunted black caimans for their skins, which make shiny black leather, and hunting cut the number of black caimans by approximately 99 percent in the 20th century, as an estimate. Clearing forest and burning swamps destroys black caiman homes and slows the recovery of their numbers. As of March 2013, some countries, such as Brazil, had given the black caiman legal protection, and in 1990 Bolivia began a program to breed black caimans in captivity and set them free in the wild. Large predators like the black caiman can shape the community of animals around them. Black caimans live in the slow rivers, lakes and flooded land of the Amazon.

Words to know

• floodplain: river flood land
• crustaceans: shelled water animals
• census: count of animals
• clutch: group of eggs