2,000 dead mice dropped on Guam by US helicopters to kill snakes

Brown tree snakes have caused numerous costly problems

US authorities have launched an unusual mission to kill troublesome snakes in Guam - parachuting in 2,000 dead mice laced with deadly painkillers.

The brown tree snakes have caused numerous problems at Andersen Air Base on the remote Pacific island, between Japan and Indonesia, one of the most strategically important US bases in the region.

There are an estimated 2 million of the snakes on the island, thought to have arrived stowed in a cargo shipment in the mid-20th century. They often gnaw and wriggle their way into important electrical stations, causing power failures at the base. They also threaten the population of native exotic birds, which they like to eat.

In 2005 the Interior Department estimated the damage causes up to $4 million (£2.4 million) in repair costs every year. But the reptiles are fatally intolerant to acetaminophen, the active ingredient in the consumer painkiller Tylenol.

This is the fourth and biggest attempt at the poison-parachute technique. Tino Aguon, acting chief of the US Agriculture Department's wildlife resources office for Guam, told KUAM, NBC's local outlet: "Every time there is a technique that is tested and shows promise, we jump on that bandwagon and promote it and help out and facilitate its implementation."

The mice - attached to two pieces of cardboard and green tissue paper - are dropped from low-flying helicopters.

Dan Vice, the Agriculture Department's assistant supervisory wildlife biologist for Guam, told KUAM: "The process is quite simple. The cardboard (in the mini parachutes) is heavier than the tissue paper and opens up in an inverted horseshoe. It then floats down and ultimately hangs up in the forest canopy. Once it's hung in the forest canopy, snakes have an opportunity to consume the bait."

Guam is an integrated territory of the US, ceded by Spain in 1898.