A state agency passed a plan to eradicate invasive house mice by dropping poison from a helicopter across islands near California, multiple news outlets reported.
The California Coastal Commission approved the controversial plan by a 5-3 vote on Thursday, Dec. 16, the Marin Independent Journal reported.
Under the plan, helicopters would drop 2,880 pounds of rodenticide brodifacoum pellets across parts of the South Farallon Islands to kill thousands of mice that have disrupted the area’s ecosystems, the news outlet reported.
“You can see the grass move with the mice,” U.S. Fish and Wildlife spokesman Doug Cordell told KPIX-TV in 2019. “That’s how many there are out there. So it’s plague-like infestation.”
But the federal government needs to approve the plan before it’s set in motion.
The islands — which are about 30 miles from San Francisco’s Golden Gate Bridge — are part of the Farallon National Wildlife Refuge. The refuge was established in 1909 to conserve wildlife and is closed to the public, according to the U.S. Fish and Wildlife Service.
Wildlife officials say the large mice population impacts large seabirds, the Farallon arboreal salamander, Leach’s storm-petrels, Farallon camel cricket and native plants.
The mice compete with the native salamander for food, which has caused the amphibian’s population to decrease, wildlife officials said in a Coastal Consistency Determination plan in April. And the mice attract migrating owls to stay on the island to feed on the creatures.
Seabirds also have the largest nesting colony in the southern U.S. on these islands, including the largest colony of western gulls in the world, according to the U.S. Fish and Wildlife Service.
Organizations that oppose the mouse eradication worry about poison ending up in the surrounding ocean and killing other animals and marine life. But the plan has policies in place to avoid the poison from entering waters.
The mice population was estimated to be about 60,500 within the wildlife refuge.