The brown tree snake, also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia, Papua New Guinea, and many islands in northwestern Melanesia. The snake is slender, which facilitates climbing, and can reach up to 2 metres in length. Its coloration may also vary, some being brown, green, or even red. Brown tree snakes prey on a wide range of animals, from invertebrates to birds and even some small mammals. It is one of the very few colubrids found in Australia, where elapids are more common.