evidence: Green anacondas are the world’s heaviest snakes, and among the longest. Predominantly found in rivers and wetlands in South America, they are renowned for their lightning speed and ability to asphyxiate huge prey then swallow them whole. [...] Historically, four anaconda species have been recognised, including green anacondas (also known as giant anacondas). Green anacondas are true behemoths of the reptile world. The largest females can grow to more than seven metres long and weigh more than 250 kilograms.