As of November 2026, the black caiman is the largest kind of caiman. It lives in the Amazon, a huge river area in South America, in slow rivers, lakes and flooded land. A black caiman can grow longer than 4 metres, and the biggest old males can be longer than 5 metres and weigh more than 400 kilograms. Its dark colour helps it go unnoticed in the water. Studying such an animal is difficult, because it is hard to learn what crocodilians eat when they live in water and often hunt at night.

Scientists put satellite transmitters on adult black caimans in French Guiana in May 2015. They could tag only four, which measured 2.8 to 3.5 metres. They caught the caimans at night from a small motorless boat, using a noose. At Agami Pond in French Guiana, adult caimans were found only in flooded forest, while young ones used the open water of the pond. Tracking showed home ranges from 336 to 21,511 square metres, depending on the animal and the time of year. The tracks gave strong evidence that the caimans patrol a territory, and different age classes moved in different ways.

Tests of the tagged caimans' bodies suggested that subadults and adults ate birds and fish that eat other animals. The researchers write that the black caiman eats several kinds of prey, so it is opportunistic. Over its life, a black caiman changes from eating small animals without backbones to eating animals with backbones. A young black caiman eats insects and other small animals, while a grown one is among the biggest predators in its part of the Amazon. It eats fish, such as piranhas and catfish, and it may even eat animals as big as a capybara. A capybara is a big rodent of South America.

In French Guiana the caiman's numbers fell by nearly 99 percent during the 20th century, mainly because of hunting focused on its hide. People hunted black caimans for their skins, which make shiny black leather. As of June 2019, French Guiana has fully protected the black caiman by law since 1986, and the authors say its numbers need continuous monitoring. The Kaw Marsh black caiman population is not connected to the Brazilian population. 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, and it lives in slow rivers, lakes and flooded land.

Words to know

• transmitters: signal senders
• opportunistic: taking what comes
• predators: animal hunters
• territory: guarded area