The Wild Side: Air Force helps battle an invasive species
When I was attending Colorado State University in the late 1990s, I attended a graduate student seminar that really stuck with me because I remember thinking the results were ground-breaking. John Shivik was studying predatory cues of the brown tree snake in Guam. If you are not familiar with the issue, Guam has a serious brown tree snake problem. Since the time they were accidentally introduced to the island nation over half a century ago, their population has exploded. In some areas, they have as many as 13,000 per square mile or 20 snakes per acre. The snake is an effective nocturnal predator, and has eaten most of Guam’s native wildlife into extinction, including lizards, bats and most of their birds. Shivik was studying ways to make an attractant that would lure snakes into traps. No small task, honestly—snakes hunt live prey, using senses like sight, smell and in some cases heat detection to help find food. I don’t recall all the details, but I remember a surprise result of his research was that he was catching snakes in traps where the mice had died. These snakes were eating carrion, or dead animals, as well as preying on live animals. The study intended to discover whether sight or smell was more important; the side product, discovering their taste for dead mice, would eventually tie into today’s innovative control work on this snake.
Fifteen years later, there is an aggressive brown tree snake control program in place, including using traps and snake-sniffing dogs. The newest control method is beautiful in its safety and simplicity, and frankly, it is really cool. It turns out this snake has a deadly sensitivity to acetaminophen, the ingredient in pain relievers like Tylenol. Just a fraction of one pill is enough to kill this snake. So, biologists know they live in trees, eat dead mice and die from a tiny dose of acetaminophen. All we need now is a way to get dead mice into trees, right? That’s the fun part. Leave it to the Air Force! Biologists put a small dose of the drug into a dead mouse, attach it to a parachute and drop it out of an Air Force helicopter with a couple thousand others. The medicated mice hang up in the tree canopy where tree snakes will feed on them. If they make it to the ground, it really isn’t a problem; other animals that might eat one, like dogs or pigs, would have to eat several hundred of the mice to risk a lethal dose. Some of the mice have tiny radio transmitters as well, so when the snake eats it, they can track it to see how far it travels and where and when it dies.
Invasive species can have a devastating effect on native wildlife, habitat and people. Biologists around the world work on reducing damage caused by animals illegally or accidentally introduced. You may recall me writing about pythons in Florida, grey squirrels in England, or raccoons in Germany and Japan. Guam’s snake invasion is another huge invasive species problem on a small, isolated land mass. The U.S. government has funded this $8 million rodent paratrooper program to try to cut down on the losses of wildlife, domestic poultry and even the numbers of snake bitten children and costly power outages they have caused. Will this control method actually turn the tide? Will it lead to effective control methods for other invaders? Only time will tell. Either way, it’s a cool application of science, ingenuity and the Air Force.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.