By Dr. Robert Thorson

Imagine you’re on your favorite beach enjoying a good book. Into your lap falls a dead mouse tied to a whirling streamer. What do you do? On a Connecticut beach, you freak out. But if you’re on Guam, you brush it off as business as usual, knowing that federal officials are just doing their best to control a major problem.

Truth is sometimes stranger than fiction. This clearly applies to the case of the brown tree snakes of Guam, a U.S. protectorate in the tropical Pacific. To rid the island of them, sober civil servants of the U.S. Department of Agriculture are dropping dead mice into the treetops to deliver lethal painkillers to the serpents. This takes the concept of “mouse droppings” to an entirely new level.

This plan was a real jaw dropper for me when I learned of it in February. My initial instinct was to immediately share this “weird science” with my readers during winter’s doldrums. Instead, I decided to save it to help inaugurate their summer reading.

Beneath the apparent absurdity is my strong opinion about the great cost of controlling stowaway species. A stitch in time saves nine.

The big concern is Hawaii, which is why shipments leaving Guam are carefully examined for stowaway snakes. In Hawaii, the economic damage of an invasion is estimated to be in the range of $400 million, and the ecological cost is unthinkable.

The story began when a single pregnant female or breeding pair of Boiga irregularis came to Guam, most likely hiding on U.S. military equipment being moved from the island of Manus in New Guinea. Ironically, this costly invasion followed the costly U.S. invasion to drive the Japanese to surrender, following their invasion after Pearl Harbor.

Once on Guam, the brown tree snake became a wildly successful invasive species: an apex predator with no natural enemies and plenty to eat. Its hunting technique is to slither silently through the trees, especially at night, or lie in wait for an ambush. One quick strike and one venomous bite later, and some prey animal becomes a meal that helps nourish the next generation of snakes. Because birds were their favorite prey, the bird populations plummeted as the snake population expanded. The forest became eerily silent.

By this time, residents and tourism officials had become seriously alarmed. The initial hope was that the snake population would crash when they ran out of birds to eat. Unfortunately, they switched to eating other fare, mainly small mammals and other animals, decimating those populations as well.

Now the brown snake population is high enough to scare the tourists away. They’re creeping up power poles and shorting out the electrical grid, creating “brownouts.” The snakes, which grow up to 10 feet long, have bitten humans with nonlethal but venomous bites. The spider population has exploded thanks to the loss of their bird predators. Ditto for other creepy crawlers.

Getting rid of the snakes is a major technical challenge because they live, breed and feed in the high tree canopy and are nocturnal. And it’s been hard finding a poison that would kill the snakes, but nothing else. After several research trials, however, officials came up with a strategy they think will work. The main trial is underway.

In your medicine cabinet may be the familiar painkiller acetaminophen, aka Tylenol. Luckily, this chemical is lethal to brown tree snakes, but not other creatures. Luckily, the snakes will eat dead prey. So, the plan is to raise boatloads of mice for bait, kill them, and then — here’s the most absurd part — dose them with painkiller after they’re dead. Next, tie each mouse to a streamer to slow its descent and make sure it gets caught in the trees. There they will dangle until smelled by a forked tongue and eaten as a meal.

Poisoned, the snake falls to the ground with a thud, providing a happy ending to an almost unbelievable cautionary tale.