As of November 2026, the black caiman is the largest kind of caiman. It has dark skin, large eyes and a narrow snout, and its dark colour helps it go unnoticed in the water. A black caiman can grow longer than 4 metres, and a table from the Food and Agriculture Organization of the United Nations lists its total length as 300 to 400 centimetres, with 500 centimetres as the maximum. The biggest old males can be longer than 5 metres and can weigh more than 400 kilograms. Huge black caimans of 6 metres have been reported, but these reports are not confirmed.

A black caiman has acute sight and hearing, which help it hunt at night. At night, people find black caimans by the bright orange shine of their eyes in a light. It hunts mostly in the water, but it may come onto land to hunt, usually at night. A grown black caiman is among the biggest predators in its part of the Amazon. Over its life, it changes from eating small animals without backbones to eating animals with backbones. It eats fish, such as piranhas and catfish, and it may even eat animals as big as a capybara.

A mother black caiman builds her nest in the dry season. A black caiman nest is a mound about 1.5 metres across, made of earth, leaves and sticks. Most nests are in flooded forest around lakes cut off from the river. Sunlight or the heat of rotting plants can warm a nest. A clutch holds 21 to 75 eggs, each weighing 90 to 155 grams, and the eggs take 60 to 90 days to hatch. Many females nest close together, so many hatchlings can be in one area. This leads to safety in numbers.

The eggs often hatch when the rainy season begins, and the mother opens the nest when they are ready. A newborn black caiman is about 30 centimetres long. Baby black caimans stay together in groups. Pods of baby black caimans may hold young from more than one nest, and an adult female is often nearby to protect them. A young black caiman eats insects and other small animals. One source says a black caiman reaches adulthood at around 8 years old or at a length of about 2 metres.

A black caiman's home range can be under 1 hectare in the low-water season and grow to 20 hectares in the rainy season. In a drought, a black caiman may stay buried in the mud on the bottom until the rains return. It lives in the slow rivers, lakes and flooded land of the Amazon, a huge river area in South America.

Words to know

• predators: animal hunters
• capybara: big rodent
• clutch: group of eggs
• hectare: large land area
• hatchlings: newly hatched young