Green Anaconda

The green anaconda is not the longest snake in the world — that title goes to the reticulated python — but it is the heaviest by a wide margin. It is a semi-aquatic ambush predator of South America’s wetlands, built like a fire hose and strong enough to subdue a caiman.

Overview

Green anacondas live in the warm, slow-moving waters of northern South America: the flooded forest of the Amazon and Orinoco basins, and the seasonally inundated grasslands of the Venezuelan and Colombian Llanos, where they are most easily studied. They spend the majority of their time in or beside water, which supports their enormous weight and hides their approach.

Physical characteristics

An adult green anaconda is olive to greenish-brown with two rows of black oval blotches down the back — camouflage in muddy water and dappled shade. The eyes and nostrils sit on top of the head, so the snake can watch and breathe while almost completely submerged.

Most wild adults are 3–5 m long. Reliable records of over 6 m and 100 kg exist, and unverified claims of much larger animals have circulated for centuries without solid evidence. Females are dramatically larger than males — often four to five times the weight.

Hunting and feeding

The anaconda is a constrictor and hunts by ambush. It waits, motionless, at the water’s edge or just below the surface, and when prey — a capybara coming to drink, a caiman, a wading bird, a deer — comes within reach, it lunges, seizes the animal with its many recurved teeth, and throws coils around it. The coils do not crush; they tighten incrementally with the victim’s own breathing until blood circulation and the heartbeat stop, usually within a few minutes. The snake then works its jaws over the carcass and swallows it whole. After a large meal an anaconda may not eat again for weeks or months.

Reproduction and life cycle

Breeding happens in the dry season, when receding water concentrates snakes. Several males may find a large female by scent and coil around her for days or weeks in a breeding ball, competing slowly for the chance to mate.

The female is ovoviviparous — the eggs develop inside her body and she gives birth to live young, typically 20 to 40, each 60–90 cm long and fully independent. Newborn anacondas are vulnerable to birds, caimans, other snakes, and larger anacondas, and only a fraction survive their first year.

Threats and conservation

The green anaconda is listed as Least Concern; it remains widespread and there is no evidence of a broad decline, though no reliable population estimate exists. Local pressures include:

• Killing out of fear wherever the snake is found near people or livestock.
• The skin trade and, increasingly, collection for the exotic pet trade.
• Habitat loss as wetlands are drained and rivers dammed, and pollution from mining and agriculture in parts of the range.

In 2024, a genetic study proposed that anacondas in the far north of the range represent a separate species, the northern green anaconda — a reminder of how much about even the world’s most famous giant snake is still being worked out.