What Do Anacondas Eat? Capybaras, Caimans and Fish

The anaconda menu

The green anaconda is an apex predator: as an adult, it has very few natural enemies, and it can eat animals as heavy as itself. Its diet changes with age and size.

Field studies in the Venezuelan llanos and the Peruvian Amazon found that large anacondas regularly take big prey, often 14 to 50 percent of their own body weight. Caimans and capybaras are among the most important large prey items, along with wading birds, which crowd the remaining water in the dry season.

Do anacondas eat caimans?

Yes. Spectacled caimans and other small caiman species are regular prey, especially young and medium-sized caimans. A caiman of about 1.5 m (5 ft) has been found inside a large female anaconda in Trinidad. Fights with caimans can be dangerous for the snake too, since a caiman can bite hard while being coiled.

The relationship works both ways. Black caimans and Orinoco crocodiles are among the few animals that occasionally kill and eat adult anacondas, and many caimans eat baby anacondas.

How anacondas hunt

An anaconda is a sit-and-wait predator. It lies in shallow water, often under floating plants, with only its eyes and nostrils above the surface, which sit on top of its head. It may wait for hours near places where animals come to drink or cross.

When prey comes within reach, the anaconda strikes fast and grips with dozens of sharp, backward-curving teeth. It is not venomous. Within seconds it throws loops of its body around the animal. Each time the victim breathes out, the coils tighten. Research on constricting snakes shows that this pressure quickly stops blood circulation, so the prey loses consciousness and dies much faster than from suffocation alone.

Anacondas have an extra advantage: water. If the snake can pull prey under the surface, drowning helps subdue it and reduces the risk of being kicked or bitten. Anacondas also sometimes climb into low trees after iguanas or birds, and they occasionally eat carrion.

How do anacondas swallow such large prey?

Snakes cannot chew, so an anaconda must swallow its meal whole, usually head first so that legs and fur fold backward. Its lower jaw is split at the front, joined only by a stretchy ligament, and the bones of the skull are loosely linked. The snake “walks” its jaws over the prey, one side at a time, while its throat and body stretch around it.

Swallowing a capybara can take a long time, and the snake breathes during the process by pushing the opening of its windpipe forward along the floor of its mouth. For more on this remarkable process, see how do snakes swallow large prey?.

How long does an anaconda take to digest a meal?

Digestion is slow and depends on the size of the meal and on temperature. A large meal can take many days, and for very big prey more than a week, before it is fully broken down. Strong stomach acids and enzymes dissolve almost everything, including bones, though hair and some scales may pass through.

During digestion, the anaconda is sluggish and stays hidden. Because cold-blooded reptiles use little energy, a well-fed adult may then fast for weeks or months. Females often go most of their six-to-seven-month pregnancy with little or no food. Read about the fasting records of other snakes in how long can snakes go without eating?.

Cannibalism: females that eat males

The green anaconda is one of the few snakes in which cannibalism has been recorded repeatedly in the wild. Most cases involve a large female eating a smaller male, sometimes around the breeding season.

Scientists suggest several reasons. Females are several times heavier than males, so a male is easy prey. A female also needs a large amount of energy to carry a litter for months without hunting. A nearby male, possibly one she has just mated with, offers a large meal at little risk. This does not happen after every mating, and most males leave unharmed.

Do anacondas eat people or pets?

Many legends describe anacondas swallowing people, but there is no verified case of a green anaconda eating a human. Pythons in Asia have killed and swallowed people in a handful of documented cases, as described in can a snake eat a human?.

Near villages and ranches, large anacondas occasionally take domestic animals such as chickens, dogs, sheep and young cattle. This is one reason people sometimes kill anacondas, along with fear. Anacondas normally avoid humans, and the safest approach with any large wild snake is to keep your distance.