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.
Learn more: Brown Treesnake Research on Guam
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- FAQ
How is the USGS helping to prevent the spread of the brown treesnake?
Preventing the spread of the invasive brown treesnake (Boiga irregularis) is paramount. Without rigorous prevention, control (let alone removal) of an introduced reptile species is extremely difficult. In the case of the brown treesnake, prevention efforts include working to detect stowaway snakes before they leave the island, as well as extreme vigilance on islands where the snakes are most...
What is an invasive species and why are they a problem?
An invasive species is an introduced, nonnative organism (disease, parasite, plant, or animal) that begins to spread or expand its range from the site of its original introduction and that has the potential to cause harm to the environment, the economy, or to human health. A few well-known examples include the unintentional introduction of the West Nile virus, chestnut blight, the South American...
Are invasive snakes dangerous?
Free-ranging snakes representing dozens of species from around the world are discovered in the United States in any given year, usually as a result of escapees or releases from the pet trade, but most of these don't appear to have established a reproductive population. Any animal can be problematic when released in places where it is not native. For example, the brown tree snake was introduced to...
Are there invasive reptiles other than Burmese pythons in the United States that people should be concerned about?
Free-ranging, non-native reptiles representing dozens of species from around the world escape or are illegally released in the United States every year. Many of these species fail to establish reproductive populations, but some are successful. Florida is a major transportation hub and has a climate that’s suitable for many invasive species, so the state has the world’s largest number of...
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Human fatalities from non-venomous snakes are very rare, probably averaging one or two per year worldwide. All known constrictor-snake fatalities in the United States are from captive snakes; these are split between deaths of snake owners who were purposefully interacting with their pet and deaths of small children or infants in homes where a snake was kept captive as a pet. There have been no...
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