Death From the Skies! Poisonous Mouse Paratroopers Bomb Guam.

Wild Things
Slate’s animal blog.
Dec. 4 2013 12:46 PM

Death From the Skies!

Brown tree snake, Boiga irregularis.
This is the enemy. Mouse bombs away!

Courtesy U.S. Fish and Wildlife Service/National Digital Library

The brown tree snake has waged an extremely successful war in the jungles of Guam ever since it invaded the island in the 1950s. There are now more than 20 snakes for every acre of land, killing native species and disrupting electrical power systems.

But never fear, for backup has been called in. Paratroopers are drifting down from helicopters above to combat the snakes. The parachutes, however, are made of cardboard and green tissue paper, and they’re designed to get snared in tree branches. Their cargo? Dead neonatal mice. Their mission? Get eaten.

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The mice, often targets of poison here at home, have become the poison themselves. Each dead mouse is implanted with a tablet containing 80 mg of acetaminophen, the active ingredient in Tylenol. While we humans might pop a pill or two to ease a headache or sore back, the chemical interferes with the ability of snakes’ blood to carry oxygen.

After the seemingly tasty snack is dropped on their arboreal doorstep, the snakes choke down their medicine. Soon a coma sets in. Within 60 hours the snakes, which grow to between 3 and 6 feet in length, are dead.

After a successful test in 2001, the mice were deployed in 2010 and again this year. The latest drop of 2,000 mice this month was the biggest ever. 

The snakes, which originally hail from Australia and other Pacific islands, were accidentally introduced to Guam shortly after World War II. Though relatively harmless to humans, the tree-dwelling snakes have devastated Guam’s jungle ecology, driving eight species of native birds extinct. They also are the frequent culprits behind power outages on the island, which they trigger by wriggling into power substations.

Though most snakes will only eat prey that they personally killed, younger brown tree snakes are known to scavenge. The poison-pill mice are targeted at these snakes, which have yet to reproduce, further controlling population.

With an estimated 2 million snakes calling Guam’s jungles home, a mere 2,000 mice won’t solve the problem. But it’s a start, and when it comes to fighting invasive species, novel techniques like this airborne division may be the only way to win the war.

Nicholas Duchesne is a Slate intern.