The green anaconda is the world's largest snake species. These giants may reach lengths of more than 29 feet and weigh more than 550 pounds. The snakes are native to the marshes, swamps and streams of tropical rain forests in South America's Amazon basin.
Female green anacondas weigh significantly more than males. Its cousin, the reticulated python, may reach greater lengths, but an enormous girth more than 12 inches in diameter makes the green anaconda king. Stealthy and sleek in the water, they are known for terrorizing larger animals all over the continent. Smaller species found in South America include the yellow, dark-spotted and Bolivian anacondas.