Science | December 18, 2021 6:32 am

California Officials Approve Helicopter Poison Plan for Invasive Mice

The plan is not without some complications

SE Farallon Island
The islands' ecosystem is getting unpredictable.
Jan Roletto

Travel 28 miles west off the cost of San Francisco and you’ll find yourself on the Farallon Islands. Although in this case, “on” might not be the best choice of words — the islands are a wildlife preserve, and they’re largely off-limits to the general public. (There’s one exception, accessible via zip line.) The islands are noteworthy for their bird population — and for the whales found in the waters surrounding them.

Unfortunately, it’s a very different creature that has a number of scientists worried, and which may lead to a dramatic response from the local government. The Guardian reports that state officials have approved a plan that involves using helicopters to drop poisoned bait onto the islands. Why? The answer is very simple: mice.

Specifically, an influx of invasive mice that have been deemed a threat to other species on the island, including birds and salamanders. Sailors first brought mice to the islands in the 19th century, and their numbers have grown since then, putting native species on the islands at risk.

The plan comes from the U.S. Fish and Wildlife Service, and the relevant state body approved it by a 5-3 vote. If that seems close to you, you’re correct — the proposed plan, which would begin in 2023, has some drawbacks, including concerns that birds might consume the poisoned bait themselves.

Even if the plan goes perfectly well, there’s also a risk that raptors might eat the bodies of poisoned mice and suffer adverse consequences from that. There are few easy answers here, unfortunately — just questions over the acceptable cost of preserving an ecosystem.