With a maximum length of around 5 to 6 m (16 to 20 ft) and a mass of over 450 kg (1,000 lb),[6] it is the largest living species of the family Alligatoridae, and the third-largest crocodilian in the Neotropical realm.

The banding on young helps with camouflage by breaking up their body outline, on land or in water, in an effort to avoid predation.

A carnivorous animal, the black caiman lives along freshwater habitats, including slow-moving rivers, lakes and seasonally flooded savannas, where it preys upon a variety of fish, reptiles, birds, and mammals.

[8] Being an apex predator and potentially a keystone species, it is generalist, capable of taking most animals within its range, and might have played a critical role in maintaining structure of the ecosystem.

Mothers on guard near their nests are tormented by blood-sucking flies that gather around their vulnerable eyes, leaving them bloodshot.

Black caimans are apex predators with a generalist diet, and can take virtually any terrestrial and riparian animal found throughout their range.

Hatchlings mostly eat small fish, frogs, and invertebrates such as molluscs, crustaceans, arachnids, and insects, but with time and size graduate to eating larger fish, including piranhas, catfish, and perch, as well as molluscs, which remain a significant food source for all black caimans.

[32][33] Dietary studies have focused on young caimans (due both to their often being more common than large adults and to their being easier to handle), the largest specimen examined for stomach contents in one study being only 1.54 m (5 ft 1 in) notably under sexually mature size, which is at a minimum 2 m (6 ft 7 in) in smaller females.

[34][35][36][37] Fish were the main prey of black caimans of over subadult size in Manú National Park, Peru.

[38] Various prey will be taken by availability, includes snakes, turtles, birds and mammals, the latter two mainly when they come to drink at the river banks.

Mammalian prey mostly include common Amazonian species such as various monkeys, sloths, armadillos, pacas, porcupines, agoutis, coatis, and capybaras.

[12] As with all crocodilian species, their teeth are designed to grab but not chew, so they generally try to swallow their food whole after drowning or crushing it.

[51] Many predators, including various fish, mammal, reptile and even amphibian species, feed on caiman eggs and hatchlings.

The black caiman shares its habitat with at least 3 other semi-amphibious animals considered apex predators, usually able to co-exist with them by focusing on different prey and micro-habitats.

These are giant otters which are social and are obligate aquatic foragers and piscivorans, green anacondas which are predators of other caiman species, alongside sizable individuals of this caiman (albeit not regularly),[52][53] and jaguars, which are the most terrestrial of these and focus their diet mainly on relatively larger mammals and terrestrial reptiles.

They are possibly the most opportunistic but, despite being the largest predator of the area, can metabolically live off of their food longer and thus may not need to hunt as frequently.

Green anaconda, jaguars and black caiman arguably sit atop this food chain.

However, adult black caimans have no natural predators, as is true of other similarly-sized crocodilian species given the size, weight, bite force, thick hide, and immense strength.

Local people still trade black caiman skins and meat today at a small scale but the species has rebounded overall from the overhunting in the past.

Due to their greater numbers and faster reproductive abilities, the Spectacled populations are locally outcompeting black caimans, although the larger species dominates in a one-on-one basis.

[20] After the depletion of the black caiman population, piranhas and capybaras, having lost perhaps their primary predator, reached unnaturally high numbers.

[58] Most tales are poorly documented and unconfirmed but, given this species' formidable size and strength, attacks on humans are quite often fatal.