Panel to consider poisoning mice that plague Farallones
Federal officials are moving forward with a plan to bombard the Farallon Islands with thousands of poison pellets in an attempt to exterminate all the mice on the rocky archipelago 27 miles off the coast of San Francisco.
The U.S. Fish and Wildlife Service issued an environmental report in March that recommends blanketing the 10 rocky islands and islets known as the South Farallon Islands with enough rodenticide to exterminate tens of thousands of invasive house mice that have taken over the only inhabited outcropping in the group and are threatening the native wildlife in the entire cluster.
The California Coastal Commission will hold a public hearing Wednesday on the plan, which created a furor six years ago when federal officials and conservation groups last brought it up. The commission, which has no power to veto the
plan, is expected to decide only whether it complies with its coastal management rules.
“At their peak, there are more than 1,200 mice per acre and they have an impact across the board,” said Doug Cordell, spokesman for Fish and Wildlife, which manages 580 wildlife refuges, including the Farallones. “The ecosystem is out of whack, and the mice are the cause of it.”
The proposal, which needs final approval from the various state and federal agencies, is to make two helicopter drops two to three weeks apart of food pellets laced with brodifacoum, an anticoagulant that causes rodents to bleed to death. Cordell said 1.15 ounces of poison would be mixed in with 2,917 pounds of a cereal substance, enough to kill every mouse.
The brodifacoum would last five weeks before the deadly ingredients dissipate, likely causing the inadvertent poisoning of gulls and other species, but experts say the ultimate effect on the island ecosystem would be positive.
Animal rights groups have opposed air drops since the idea was first considered, and their representatives are expected to crowd into the meeting in San Luis Obispo on Wednesday.
“To say ‘well, let’s just dump a bunch of poison on them. What could go wrong?’ is a very, very bad precedent to set,” said Alison Hermance, the spokeswoman for the conservation group WildCare. “To us that’s everyone’s attitude who uses poison, and it is why there is so much rat poison out there. It is the wrong message to send, and the wrong approach to a nuisance problem.”
Several other conservation groups, including California Audubon, the American Bird Conservancy and Point Blue Conservation Science, which has researchers stationed on the island yearround, support the plan. The Coastal Commission staff has said the eradication plan is consistent with its coastal management program.
“We care immensely about the islands and the wildlife,” said Zach Warnow, spokesman for Point Blue. “We would never do this if we didn’t think this was in the longterm best interest of the islands as a whole and the species that rely on them.”
It is believed the Eurasian house mice escaped from 19th century sealhunting ships visiting the rugged 120acre island chain, a place so treacherous that American Indians called them “Islands of the Dead” and European mariners dubbed them the “Devil’s Teeth.” The rodents multiplied at a feverish pace over the last century. Researchers say their densities are now the highest of any island in the world.
It’s so bad that the ground sometimes appears to be moving around the 124yearold Victorian house on what is known as Southeast Farallon Island, which scientists use to study the island ecosystem, biologists say.
The teeming hordes of mice are devouring the islands’ insects and spiders, the same food that the endemic Farallon arboreal salamander needs to survive. They have also been blamed for spreading invasive plant seeds, which stick to their fur, according to island biologists.
Worst of all, the mice attract burrowing owls, which feed on the rodents until their population crashes in the winter. The owls then begin eating the Ashy storm petrel, a small gray seabird that is listed as a species of special concern in California. Half of the 8,000 Ashy storm petrels in the world feed and nest on the Farallon Islands. Researchers say at least 225 of them are killed each year by burrowing owls.
The rodents are the last remaining nonnative mammals on the archipelago, which is one of the richest marine environments on the globe, supporting as many as 300,000 seabirds at a time, the largest colony in the continental United States.
The eradication plan, if ultimately chosen, would require teams of biologists to first scare away gulls, which would be most in danger of secondary poisoning, Cordell said. Peregrine falcons, burrowing owls and other predatory birds would be captured and held until it is safe for them to be released.
The 300page environmental document produced by federal researchers analyzed and dismissed dozens of other possible mouse control methods, including feral cats, snakes, trapping and sterilization. Cordell said cats and snakes were eliminated because they would pose a threat to birds. Trapping and rodenticide bait stations were ruled out because inaccessible terrain would make it impossible to get all the mice.
There are no known mice diseases or pathogens that could be introduced, and nobody has ever effectively used fertility drugs, sterilization or genetic modification in a rodent eradication effort.
Poison has succeeded in eradicating rodents on islands in Mexico, the Caribbean, the South Pacific, the Aleutians and the Galapagos chain, wildlife officials said. Rats were removed from Anacapa Island, in Channel Islands National Park, about 15 years ago using an aerial drop. House mice have been eradicated from more than 50 islands worldwide, officials said.
Opponents argue that in each case other species were killed, but biologists have said the island ecosystems typically recovered quickly after the invasive rodents were removed.
Cordell said federal officials are expected to make a final determination about the eradication program in the next few weeks.