‘Use your brains here.’ Plan to dump rat poison on Bay Area islands draws criticism

The Farallon Islands, seen from the south.
The Farallon Islands, seen from the south. U.S. Fish and Wildlife Service

Dozens of people have written letters protesting a federal government plan to dump rat poison on the Farallon Islands National Wildlife Refuge, a collection of rugged islands 27 miles west of San Francisco.

The islands are home to the largest seabird breeding colony in the contiguous United States, as well as one of just two northern fur seal rookeries located south of Alaska. They’re also a prime spot for shark and whale watching.

The U.S. Fish and Wildlife Service argues that dropping 2,900 pounds of bait containing brodifacoum on the islands is the best approach to eradicating the island’s invasive house mouse population “due to its documented record of island mouse eradication success,” according to a staff report presented to the California Coastal Commission.

The Coastal Commission is scheduled to review the proposal at its July 10 meeting in San Luis Obispo. The commission at its meeting cannot prevent Fish and Wildlife from carrying out its eradication plan, but the state agency can ask for accommodations or take the federal government to court to block it.

Introduced in the 19th century, house mice have caused harm to an environmentally sensitive habitat, the feds argue. The mice feast on native plants, local insects such as the Farallon camel cricket and even the eggs of amphibians like the Farallon arboreal salamander and birds like the Cassin’s auklet.

The mice also make an off-season meal for burrowing owls, which themselves are invasive to the island. When the mouse population, reaching 490 per acre at its height, crashes, the owls switch to eating local fauna, including ashy storm petrels, “thus disproportionately affecting the native species populations,” according to a memo from ecologist Lauren Garske-Garcia to the Coastal Commission.

Commission staff considered 49 “potential mice removal methods,” including “mechanical, biological, and chemical methods using different delivery techniques” before settling on recommending brodifacoum. The federal government has been developing the plan since 2011, and first published an environmental study describing its options in 2013.

Map of refuge.jpg
U.S. Fish and Wildlife Service

The project would take an estimated seven weeks, would use a total of 1.16 ounces of the rodenticide hidden in nearly 3,000 pounds of bait.

“Bait would be systematically applied to all land areas of the Refuge above mean high water by a GPS-guided helicopter,” according to the staff report, with up to 12 acres of caves and intertidal zones requiring hand-baiting.

In recommending the action, commission staff argued that the danger to local creatures, including marine life, and water quality is negligible.

Kim Sandholt, of San Rafael, isn’t convinced.

“Do you not realize that rat poison is secondary, and not only will you be killing the mice, you will be killing everything that comes in contact with the poison and the dead mice? Including getting into the water. Of course you do, because you have what looks to be very knowledgeable staff working at the CCC,” Sandholt wrote in a letter opposing the poisoning.

She was one of four dozen people to weigh in on the project.

Michelle MacKenzie, of Menlo Park, wrote that she is a frequent visitor to the Greater Farallones National Marine Sanctuary and said she is concerned at the choice of poison being used.

“The compound to be dropped is outlawed for retail sale in California because it causes secondary poisoning of other animals who ingest poisoned animals,” she said. “It is reasonable to assume that gulls or other species could ingest this poison and secondarily poison other animals.”

Secondary poisoning is when an animal, such as the house mouse, consumes the poison, dies and then is consumed by another animal in turn. According to the National Pesticide Information Center, brodifacoum has the highest risk of secondary poisoning for both mammals and birds.

Josette Brose-Eichar of Sonoma urged the California Coastal Commission to “use your brains here.”

“In my mind I see sea gulls flying back to shore after eating this stuff and slowly bleeding to death and dropping from the sky. This is just one of the unintended consequences of using this stuff,” she wrote.

The California Coastal Commission meets 9 a.m. July 10 to consider the measure.

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Andrew Sheeler covers California’s unique political climate for the Sacramento Bee. He has covered crime and politics from Interior Alaska to North Dakota’s oil patch to the rugged coast of southern Oregon. He attended the University of Alaska Fairbanks.