As part of a plan to eradicate brown tree snakes, mice were dropped on Guam this week to provide a poisoned snack for the invasive species.
On Monday, teams in helicopters released about 2,000 dead mice laced with the common painkiller acetaminophen across the island in the latest attempt to rid the U.S. territory of the serpents.
Brown tree snakes are sensitive to acetaminophen: a single mouse laced with 80 milligrams of the stuff can kill one snake that eats it.
This is the fourth time scientists have dropped poisoned mice on Guam to combat the brown tree snake population. Last February, teams dumped mice laced with painkillers near the island's Andersen Air Force Base.
Brown tree snakes, which can grow more than 10 feet long, have disrupted power lines and knocked out electricity to buildings near the base. While their venom is not lethal to humans, the snakes have decimated other native populations on the island, including several bird species.
The snakes, native to the South Pacific, have plagued Guam since they were accidentally introduced to the island shortly after World War II, according to the U.S. Geological Survey. Dan Vice, a wildlife services biologist with the U.S. Department of Agriculture, estimates that there may be as many as 2 million snakes living on the island, the Pacific Daily News reported.