Mice parachute into Guam to kill invasive snakes

HAGATNA, Guam — Biologists on Guam are trying to find out if mildly toxic dead mice can help eradicate an invasive species of snake that has caused millions of dollars in damages by creating power outages on the island.

Crews on Monday distributed mice packed with 80 milligrams of acetaminophen on two plots in a test to kill brown tree snakes, which were accidentally introduced to the island about 60 years ago.

Representatives from several federal agencies watched the aerial bait drop, Pacific Daily News reported.

The mice should not affect other species, said U.S. Department of Agriculture wildlife services biologist Dan Vice, who has worked on snake eradication for more than a decade.

“The risk to nontargets is slight,” Vice said. “It would take 500 baits to kill a pig (or dog and) 15 baits to kill a cat.”

A pilot project with 280 mice in 2010 led to more aerial bait drops that began in September. Research and the drops have cost $8 million annually with funding from the Interior and Defense departments.

An estimated 1 to 2 million snakes live on the island. Aerial bait drops might be the most efficient way to control the population without affecting deer or pigs, Vice said.

“If it proves to be successful, then we may potentially start ramping up the efforts and doing this on a larger basis across more of Guam,” Vice said.

Mice were dropped Monday on two 136-acre plots, a combined area about the size of 210 football fields. Some mice were implanted with tiny radios to allow the USDA to determine whether mice were eaten.

Biologists are also tracking populations of small animals, which will increase with fewer snakes.

The mice drops are only for area where humans don’t live, Vice said.

No deaths from the venomous bite of a brown tree snake have been recorded, Vice said. Most bites cause no more damage to an adult than a bee sting, he said. But Brown tree snakes cause problems by creating outages on the Guam Power Authority power grid with damage reaching $1 million to $4 million annually, according USDA documents.

Major substations use special fences to keep snakes out. Traps on fences catch about 8,000 snakes per year, Vice said.

A stable population of brown tree snakes could be disastrous to Hawaii, Vice said, and the threat of them spreading is real. Guam ports use snake-sniffing dogs to detect invasive species.