Either of two South American snake species in the genus Eunectes (family Boidae) that constrict their prey. The heavily built giant anaconda, or great water boa, is usually not more than 16 ft (5 m) long but can be longer than 24 ft (7.5 m), rivaling the largest pythons in length. The yellow anaconda is much smaller. Typically dark green with alternating oval black spots, the giant anaconda lives along tropical rivers east of the Andes and in Trinidad. It kills at night by lying in wait in water; it constricts prey as large as young pigs or caimans and occasionally forages in trees for birds. It may bear 75 live young at a time.