There is some debate about the maximum size of Anacondas and there have been unverified claims of enormous snakes alleged to be as long as 30 – 45 metres (98.4 – 147.6 feet). Some Anacondas, which live in the water, can reach up to 30 feet in length.

Female anacondas are significantly larger than males, having the largest sexual dimorphism of all the snakes.

The Anaconda diet includes deer, wild pigs, birds and large rodents and also aquatic animals such as fish and reptiles (caiman). Anacondas swim well and kill their prey by strangling them. If that does not work, they drown them. These snakes can survive years without eating.

Anacondas also typically feed on tapirs, capybaras, peccaries, turtles, sheep and dogs. They have been known to occasionally prey on jaguars and attacks on humans can be confirmed, although this is rare.

The Anaconda is most active at night which makes it a nocturnal reptile. Although they are not venomous, they defend themselves by inflicting severe bites, but actually kill its prey by constriction.

The Anaconda is an amphibious snake. It gives birth to live young. Younger Anacondas feed on mice, rats, chicks, frogs and fish.