How a stowaway snake turned Guam into a silent, birdless ecological graveyard

Nature · Published 3 October 2026 Swipe more like this →

In short: After World War II, the brown tree snake hitched a ride to Guam, where it found an island paradise with no natural predators. The resulting population explosion decimated native bird species, caused thousands of power outages, and forced a desperate, multi-million dollar war against a master of arboreal stealth.

The brown tree snake, a slender, nocturnal colubrid native to coastal Australia and parts of Melanesia, is a biological anomaly in its invasive range. While typically reaching 1 to 2 metres in its home territory, the lack of competition on Guam has allowed individuals to grow up to 3 metres. These snakes are generalist predators, shifting their diet from lizards to birds and mammals as they mature. Their ability to navigate tiny spaces and climb smooth surfaces—using a newly discovered 'lasso locomotion'—makes them nearly impossible to contain.

The ecological fallout on Guam has been catastrophic. The snake is responsible for the extinction of twelve native bird species, including the Guam flycatcher and the Mariana fruit dove. This predation has triggered a cascade of negative effects: with fewer birds and fruit bats to act as pollinators, the island’s plant diversity has suffered. The snake's impact is not merely ecological; it is also economic. Between 1991 and 1997, these snakes caused an average of 133 power outages annually, resulting in an estimated 4.5 million dollars in total economic loss.

Eradication efforts have been complex and costly. Researchers have deployed aerial baiting with acetaminophen-laced mouse carcasses, which are toxic to the snakes, and utilized canine inspection units at ports to prevent the species from spreading to Hawaii or the continental United States. Despite millions in funding from the Department of the Interior and the Department of Defense, total eradication remains elusive. On islands like Cocos, traditional trapping failed because the snakes preferred abundant natural prey over artificial lures, proving that this invasive species remains one of the most difficult ecological challenges of the modern era.

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