Brown tree snakes are about 15 inches in length at hatching and may reach 10 feet in length as adults; however, most snakes on Guam are 3 to 4 feet long. This snake is a rear-fanged semi-constrictor and is mildly venomous. Although the brown tree snake will readily strike when aggravated, it does not present a danger to adults. However, infants less than 6 months may be at risk from both brown tree snake bites and constriction.
The brown tree snake is an adept climber and inhabits trees, shrubs, and forests. They spend days coiled in a cool and dark location, such as a treetop or in a rotted log. At night, they become active and search for prey.
The brown tree snake is abundant on Guam with localized estimates reaching 20 or more snakes per acre of jungle. These population density estimates are among the highest snake densities ever recorded.