Strong Medicine: Over-the-counter remedy snags snakes

Acetaminophen has a powerful reputation for vanquishing pain. Wildlife-control specialists now report that the drug, the active ingredient in Tylenol and various other painkillers, can also relieve a longtime headache on Guam–brown tree snakes.

SNAKE HANDLER. The active ingredient in Tylenol kills brown tree snakes, the bane of Guam. USDA/APHIS Wildlife Services

Since this marauder appeared on the island in the 1940s, the population density of the mildly venomous reptile has mushroomed to between 13,000 and 26,000 per square mile. Growing to more than 6 feet, a brown tree snake can swallow lizards, rabbits, puppies, piglets, and endangered birds. Several have even taken a bite out of a baby. Prowling overhead power lines, members of the species, Boiga irregularis, occasionally short-circuit wires and cause local blackouts.

Because the snake lacks natural predators on Guam, the only long-term control strategy is targeted poisoning, according to scientists at the Agriculture Department’s Animal and Plant Health Inspection Service in Fort Collins, Colo. In an upcoming issue of Environmental Science and Technology, they report that acetaminophen offers the most promising pesticide for the job.

In tests, John J. Johnston and his colleagues gave 30 caged snakes dead, newborn mice with two 40-milligram acetaminophen tablets packed inside. Though nearly every snake took the bait, he says, they obviously didn’t like the taste. One-third quickly regurgitated the treated mouse. But no matter. Each snake that swallowed the bait, even temporarily, died within 3 days. All 15 snakes given mice baited with acetaminophen-free tablets survived the test.

This drug “is amazingly effective,” Johnston says. In light of its performance in preliminary tests, the Environmental Protection Agency had already granted the Agriculture Department temporary “emergency” approval to use acetaminophen as a pesticide solely against brown tree snakes on Guam. Now, the department is working toward more permanent approval, says Johnston.

The scientists also tested the effect of acetaminophen on potentially threatened scavengers, including crabs. As they reported at a conference on Guam last year, those data and past toxicology studies suggest that crabs, birds, rodents, and cats face little risk from the baits.

In sum, the scientists say the benefits of the newly launched poisoning program against the snakes “appear to outweigh the negligible risks to feral or other nontarget wildlife.”

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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