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Identification Characteristics

Distinguishing characteristics for the Brown Tree Snake include: bulging eyes with vertical pupils, rear fangs, a large head in relation to the body, and a brownish or greenish coloring with cross-band markings. The bands may be prominent or obscure and will vary throughout the snakes range. Juveniles are approximately 0.5m at hatching and can reach about 1m in their first year. When fully grown a mature snake can obtain lengths of 1.5m but can reach 2m. The Brown Tree Snake is aggressive when threatened. It will often raise its anterior body into a striking position, flatten the head and neck to appear larger and attempt to bite as it lunges forward. It is mildly venomous but not fatal, its bite can nevertheless cause severe sickness in young children, the elderly, or people with a weakened immune system.

Native Range

The Brown Tree Snake is native to eastern Indonesia, the Solomon Islands, New Guinea, as well as the northern and eastern coasts of Australia. Historically the Brown Tree Snake does not occur in the Philippines or farther west than Sulawesi, Indonesia. Guam is the only expanded range for the Brown Tree Snake.

Photo by S. Wisniewski
Photo by S. Wisniewski

Photo by S.Wisniewski
Photo by S. Wisniewski


Brown Tree Snake is a tropical, nocturnal, arboreal snake. Native habitat includes woodlands, wet and dry sclerophyll forests, rainforest, and rock outcrops. It often invades homes, commercial buildings, and other urban habitats in search of food and hiding places. The Brown Tree Snake is noted for its stealth and adaptability. It seeks refuge from heat and bright sunlight in the daytime and often takes refuge in hollow trees, caves, and in crevices.


Common Prey

Adult Brown Tree Snakes prey on small mammals, birds, eggs, nestlings, and lizards. Juveniles, up to about 1m in length, eat lizards exclusively. Venom is delivered into the prey animal by repeated action (chewing) of the enlarged rear teeth/fangs. The fangs have a groove, and the venom runs down the groove and into the wound. The venom is mild, roughly equivalent to a bee sting in an adult human, although babies and some elderly that have been bitten have been hospitalized with respiratory problems due to being bitten. Whether the venom helps subdue a prey item or if it is more of a digestive aid is not known at this time. Larger snakes will use constriction to help subdue bigger prey.


This is an egg-laying (oviparous) snake with clutches of 5 to 12 eggs being laid in one clutch. The eggs are abandoned by the female in caves, hollow trees, or in other places where they hatch if adequately protected from drying and overheating. Reproduction is poorly known, but depending on conditions females may lay up to two clutches per annum. On Guam the snakes can probably breed year round. The eggs hatch in approximately 90 days. The snakes are around 3 years old when they first reproduce. Females can possibly store sperm for several years, meaning that they can mate with a male, lay fertile eggs and lay another fertile clutch of eggs 2 years later from the stored sperm.

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