The only humans who occupy the South Farallon Islands off San Francisco are scientists. But the land is otherwise well-populated: In addition to sea lions, seals, and salamanders, it's home to the biggest seabird breeding colony in the Lower 48. But there's also house mice—up to 60,000 of them. The invasive mice were introduced by ships centuries ago, per the Marin Independent Journal, and as the last invasive mammal there the creatures are a scourge upon the islands' ecosystem. They draw burrowing owls that feed on both the mice and the rare ashy storm-petrels; half of those left in the world live on the Farallones. The US Fish and Wildlife Service, which manages the islands, has decided the mice need to go, and has picked a contentious eradication method: It wants to drop 1.5 tons of rat poison pellets on the islands.
The plan, which would go into effect no sooner than late 2020 if approved by the EPA and NOAA, would see cereal grain pellets containing brodifacoum released by helicopters twice in a three-week period. Owls and hawks would be "temporarily removed," per the Los Angeles Times. Seagulls that would be drawn to the poisoned mice would be scared off using fireworks and air cannons. Mice carcasses would be hand-collected but not totally removed; up to 1,700 gulls could die from eating those that remain. Critics doubt the gulls can be kept away and float the possibility of sickened ones make it to the mainland, dying, and making their way up the food chain via raccoons and mountain lions. "This is exactly how the food web is destroyed for generations," a biologist tells KTVU. The California Coastal Commission has scheduled a public hearing on the plan for Wednesday. (The Farallones have been called the most rodent-dense island in the world.)