The most common of the four species, green anacondas are large green snakes bearing asymmetrical black spots over their entire bodies, with the spots on the side having a yellow center. Reaching up to 29 feet and 550 pounds, the green anaconda is the largest snake in the world.

The Bolivian anaconda is native only to that South American country and is similar in size and coloration to the green anaconda, with olive skin and black spots. The yellow anaconda is yellow or yellowish-green and bears the same spots as other anacondas, although it is significantly smaller, reaching just 10 feet in length. The dark-spotted species native to Brazilian wetlands is dark brown in color with darker spots and similar in size to the yellow anaconda.