Brown Tree Snake

The brown tree snake (Boiga irregularis), also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia (Sulawesi to Papua), 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. Due to an accidental introduction after the events of World War II, this snake is now infamous for being an invasive species responsible for extirpating the majority of the native bird population in Guam. Currently, efforts are being made to reduce and control the population on Guam and prevent the snake from spreading to other locations. Researchers are employing various methods, including aerial baiting, to attempt to control the population, while multiple agencies continue to fund and support the species' removal.

Description

The brown tree snake is a nocturnal, arboreal species that uses both visual and chemical cues when hunting, whether in the rainforest canopy or on the ground. It is a member of the subfamily Colubrinae, genus Boiga, which is a group of roughly twenty-five species that are referred to as "cat-eyed" snakes for their vertical pupils. The brown tree snake is generally 1–2 metres (3–7 ft) in length in its native range. The snake is long and slender, which facilitates its climbing ability and allows it to pass through tiny spaces in buildings, logs, and other shaded locations, where it seeks refuge during daylight. Variations in coloration occur in the snake's native range, from lightly patterned brown to yellowish/green or even beige, with red, saddle-shaped blotches. They are rear-fanged, have a large head in relation to their body, and can survive for extended periods of time without food. The median age of maturity for these snakes is estimated to be 3.1 years in males and 3.7 years in females.

Owing to the availability of prey and the lack of predators in introduced habitats such as Guam, they have been known to grow to larger sizes than their typical 1 to 2 m (3.3 to 6.6 ft) in length. The longest recorded length of this species is one found on Guam measuring 3 m (9.8 ft).

Distribution and habitat

The brown tree snake is native to coastal Australia, Papua New Guinea, and many islands in northwestern Melanesia. The species occurs on variably sized islands, extending from Sulawesi in eastern Indonesia through Papua New Guinea and the Solomon Islands and into the wettest coastal areas of Northern Australia. The snakes on Guam represent the only documented reproductive population outside the native range. Since January 2016, however, four snakes have been sighted on the island of Saipan in the Northern Mariana Islands.