The brown treesnake is native to parts of Indonesia, the Solomon Islands, New Guinea, and Australia. The snake was first sighted on the island of Guam in the 1950s, probably after stowing away on cargo ships coming from New Guinea. In 2020, a population of brown treesnakes was discovered on Cocos Island, a small atoll of the southern shore of Guam, which represents the first instance of brown treesnakes establishing off the island of Guam.
The snakes feed on lizards, birds, small mammals, and eggs. Since the treesnake has no natural predators or other controls on Guam, it multiplied rapidly and has virtually wiped out Guam’s native forest birds. The snakes also crawl on electrical lines and cause expensive power outages and electrical damage.
Brown treesnakes are mildly venomous. While the snakes are not considered dangerous to an adult human and no known deaths have occurred, young children can have reactions to tree snake bites.
Many techniques have been discussed to eliminate the brown treesnake in Guam, but there is no known way to remove them entirely. The best management strategy is to keep them from becoming established at new locations while continuing to do research on tools such as improved traps, fumigants, toxicants, and attractants; and on control options such as parasites and viruses.