It was an odd site in Guam on Sunday, as two thousand mice floated down from the sky on tiny cardboard and tissue paper parachutes. Why were mice flying through the air? They were dropped from a plane over the Andersen Air Force Base in the United States territory of Guam on a mission to kill the brown tree snakes that have invaded the country.

The mice were already dead before being dumped, and had been pumped full of 80 mg of acetaminophen. An $8 million United States program was approved in February to help eradicate the snakes and save the wild life and exotic birds that have become the snake’s favorite snack. Sunday’s drop marked the fourth rodent air assault, and the biggest so far.

“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,” said Tino Aguon, the acting chief of the United States Agriculture Department’s wildlife resources office for Guam.

United States Department of Agriculture assistant state director supervisory wildlife biologist Dan Vice explained the process of dropping the mice. “What we’re going to be watching is the oral delivery of oral toxicans out of a helicopter,” Vice said. “The process is quite simple. The helicopter is going to make low altitude flights over the forest at relatively slow speeds they’re going to be certified pesticide applicators inside the helicopter delivering the baits out of the helicopter on a time sequence.”

He continued to explain the reason behind the parachutes and their design. “The cardboard is heavier than the tissue paper and opens up in an inverted horse shoe,” Vice said. “It then floats down and ultimately hangs up in the forest canopy. Once its hung in the forest canopy snakes have an opportunity to consume the bait.”

The program chose to use acetaminophen in the mice because it is lethal to snakes and can kill them in as short as 72 hours. Vice assures us, however, that the mice will not be lethal to any other animals that may get ahold of them.

“One reason acetaminophen is so effective for snakes is that its very low toxicity to other organisms. of all the organisms in the forest to be concerned about the monitor lizards, the iguanas is probably the one that is potentially at risk but because the baits are hung up in the forest canopy and not distributed on the floor the monitors aren’t going to encounter the baits with great frequency the monitors climb trees but they tend not to feed in trees,” he said.

Image via Wikimedia Commons