Anaconda vs Python: Which Is the Biggest Snake?

Key differences at a glance

The comparison table above sets the green anaconda against the reticulated python, the two snakes most often called the biggest in the world. Other giant pythons, such as the Burmese python and the African rock python, are big too, but none matches the reticulated python for length. In brief:

• Length: the reticulated python wins.
• Weight and bulk: the green anaconda wins.
• Continent: South America for the anaconda, South and Southeast Asia for the python.
• Lifestyle: the anaconda lives mostly in water; the python lives mostly on land and in trees, though it swims well.
• Babies: anacondas give birth to live young; pythons lay eggs.

Which is longer?

The reticulated python is the longest snake in the world. A study of more than a thousand wild reticulated pythons collected in southern Sumatra found lengths from about 1.5 to 6.5 m (5 to 21 ft). The longest scientifically measured individual, from East Kalimantan in Indonesian Borneo, was 6.95 m (22 ft 10 in) when measured under anesthesia. Snakes over 6 m (20 ft) are rare, but the reticulated python is the only living snake that reaches that length with some regularity.

Green anacondas are shorter. Adult females usually measure 3.5 to 5 m (11 to 16 ft), and the longest verified anaconda, a captive female at the Pittsburgh Zoo, reached about 6.27 m (20 ft 7 in). For the python’s full record story, including the famous Pittsburgh python “Colossus,” whose claimed 8.7 m (28 ft 7 in) shrank to about 6.35 m (20 ft 10 in) when its skeleton was measured, see how long is a reticulated python?.

Which is heavier?

The green anaconda is by far the bulkier snake. Its body is thick and heavy, while the reticulated python is long and relatively slim. According to estimates in the snake literature, a 5.2 m (17 ft) green anaconda weighs about as much as a 7.4 m (24 ft) reticulated python.

Large female anacondas usually weigh 30 to 80 kg (66 to 176 lb), and the heaviest wild one measured by researchers in Venezuela was 97.5 kg (215 lb). In the Sumatran study, reticulated pythons weighed from about 1 to 75 kg (2 to 165 lb), and the 6.95 m (22 ft 10 in) record python weighed only 59 kg (130 lb), though it had not eaten for nearly three months. The Burmese python is usually ranked as the second heaviest snake, ahead of the reticulated python.

Where do they live?

The two giants live on opposite sides of the world:

• Green anaconda: tropical South America east of the Andes, including the Amazon and Orinoco basins, the Guianas, Trinidad, and south to Bolivia and northern Paraguay.
• Reticulated python: South and Southeast Asia, from the Nicobar Islands, Bangladesh and Myanmar through Thailand, Indochina and Malaysia to Indonesia, the Philippines and Timor-Leste.

The anaconda is a snake of swamps, marshes, flooded grasslands and slow rivers. The reticulated python lives in rainforests, woodlands and nearby grasslands, usually near rivers or lakes, and it also turns up in farmland and even in cities such as Bangkok and Singapore, where it hunts rats in drains. It is an excellent swimmer and has been seen far out at sea, which helps explain how it reached many small islands.

How do they hunt?

Both are nonvenomous constrictors and ambush hunters. They wait for prey to come close, strike, grip with backward-curving teeth and wrap the animal in coils that stop its blood flow.

The difference is the setting. The anaconda hunts mainly from the water, lying with only its eyes and nostrils showing, and it can drown prey as well as constrict it. Its prey includes fish, wading birds, turtles, caimans, capybaras and deer. The reticulated python hunts mostly on land or in trees. Small pythons eat rats, bats and tree shrews; large ones take civets, monkeys, wild pigs and deer. One 6.95 m (22 ft 10 in) python had swallowed a sun bear of about 23 kg (51 lb).

Both families share the same flexible jaw design that lets them swallow prey wider than their heads. Read more about the anaconda’s menu in what do anacondas eat?.

How do they reproduce?

Here the snakes differ sharply, and the difference reflects their families. The green anaconda, like most boas, gives birth to live young. The eggs develop inside the mother for six to seven months, and she then delivers usually 20 to 40 babies, each about 70 to 80 cm (28 to 31 in) long. Mating often happens in a “breeding ball” of several males wrapped around one female.

The reticulated python, like all pythons, lays eggs. A female lays about 15 to 80 eggs in a sheltered spot and coils around them while they incubate. At warm temperatures of around 31 to 32 °C (88 to 90 °F), they hatch after about 88 days, and the hatchlings are at least 60 cm (2 ft) long. For other differences between the two families, see python vs boa.

Which is more dangerous to people?

Attacks on humans by either snake are rare, but the reticulated python has the worse record. There are several well-documented cases in which reticulated pythons killed and swallowed adults, most of them in Indonesia, especially on Sulawesi. These pythons often live near villages and plantations, where people and snakes meet.

There is no verified case of a green anaconda eating a person, despite many legends. Large anacondas could overpower an adult, but they live mostly in remote wetlands. Both species normally avoid people, and wild giant snakes should only be watched from a distance.

Myths about giant snakes

Myth: Anacondas and pythons can reach 12 m (40 ft). No snake of that length has ever been proven. A reward for a live snake over 30 ft (9.14 m), first offered in the early 1900s through the New York Zoological Society and later raised to 50,000 US dollars, was never claimed.

Myth: The anaconda is a kind of python. The two are often confused, but anacondas are boas. They look similar because both evolved as heavy-bodied constrictors.

Myth: Both species are endangered. Both are listed as Least Concern by the IUCN, though both are heavily traded for their skins and local populations can suffer from overharvesting and habitat loss.