By Kim Smiley

On December 1, 2013, 2,000 dead, poisoned neonatal mice were parachuted onto Guam on a unique mission to fight an invasive species, the brown tree snake. The parachutes are designed to catch in the trees and tempt the snakes, who live in the trees, into eating the mice. The mice are pumped full of acetaminophen, a chemical that the snakes are particularly sensitive to because it affects their blood’s ability to carry oxygen.

There are an estimated 2 million brown tree snakes on Guam so the 2,000 poisoned mice will only impact a very small percentage of the population, but scientists hope that the information they learn from this drop will help them plan larger mice drops in the future.  This is the fourth and largest dead mice drop so far and cost 8 million dollars.  Some of the mice were embedded with data-transmitting radios for this drop which will allow scientists to better gauge the effectiveness of this technique.

While the 8 million dollar price tag sounds high, it’s important to realize that the damage done by the brown tree snakes each year is significant.  Since their accidental introduction to the island, brown tree snakes have destroyed the native ecosystem, decimating the native bird population.  Brown tree snakes are also fantastic climbers and they routinely get into electrical equipment.  They cause an average of 80 power outages a year, resulting in costs as high as $4 million for repairs and lost productivity annually. (See our previous blog for more information.)

Even through the problem of the brown tree snakes is fairly well understood, an effective solution has been difficult to find.  There have been a number of different things tried over the years: snake traps, snake-sniffing dogs and snake-hunting inspectors have all been used, but the snakes have completely over un the island.  As farfetched as it sounds, parachuting dead mice seems to be the most promising solution at present.  It works because the snakes are very sensitive to acetaminophen; they only need to ingest about one-sixth of a standard pill for it to be effective.  This means that non-target animals are unlikely to be heavily impacted by the mice drops.  A pig or dog would need to eat around 500 of the baited mice for the dose to be lethal. One of the concerns is that snakes tend to avoid prey that is already dead, but information from the radio transmitters used in the recent drop should confirm if the mice are an effective bait.

One thing I know for sure, I would have loved to be in the brainstorm meeting the first time someone suggested parachuting dead mice.  This example is a good reminder to all of us to keep an open mind.  Every now and then, the most bizarre solution suggested turns out to be the best.