Locals shift to friendlier rat killers

David Briggs
A San Anselmo-based group is placing owl boxes around the county to encourage rodent predation, as part of a move away from rodenticides.
06/21/2012

At the end of last year, Bolinas Bay Lumber & Landscaping Supplies decided to stop carrying DeCon and other chemical rodenticides. Instead they began offering pest management alternatives, and are trying to educate residents about their decision to quit stocking the poison.

“We realized that birds were eating the poisoned rats,” store owner Karen Dibblee said, “and that the birds themselves then die a terrible death.”

In rural West Marin, rodenticides have long been a popular and effective way of killing the mice, rats, voles and gophers that plague farms, harass old houses and have even been known to crawl under hoods and damage vehicles.

While many folks manage to effectively fight off the scurrying hoards using the poison, it doesn’t kill its targets right away. Most rodenticides are anticoagulants, meaning they stop the blood’s ability to form clots, damage the capillaries, and result in death by internal bleeding within about 72 hours.

Because anticoagulant baits are slow acting, the animal takes a few days to perish, during which time its movements are sluggish and it can easily fall prey to house cats, hawks, owls, herons and other predators. Because the animal is unable to associate its illness with the bait eaten, it will also continue to ingest more and more of the poison.

“They are like these toxic little pills running around,” Stockton Buck, creator of the Rodenticide Free Project, said. Mr. Buck started the project a few years ago after becoming aware of the poison’s impact on the broader environment.

“We were out in Point Reyes one time, and my lady said, ‘You know, I don’t hear the owls like I used to,’” he said.

Most predators ingesting a poisoned animal become ill and can die. While sick hawks and other birds of prey brought into shelters can sometimes be treated and cured by a six-week course of vitamin K, many succumb to the poison with blood running from their eyes and nares.

Anticoagulant rodenticides were first discovered in the 1940s. But by the late 1950s, resistance to the poison had started to build up in rodent populations in Scotland. The resistance soon spread throughout Europe, and a second generation of anticoagulants were developed that were stronger and required lower doses to be fatal – although the process still took several days.

Since his first realization that Marin needed to change the way it managed its rodent population, Mr. Buck has spent the last several years working to rid the county of rodenticides. This month, the Environmental Protection Agency (EPA) announced that it is starting the process to ban the most deadly second-generation rodenticides from the consumer market.

“It would still be available to pest control professionals,” Mr. Buck said, “but you wouldn’t be able to find it on the shelves at Home Depot.”

The California Department of Fish & Game (DFG) is concerned too. In a recent letter to the California Department of Pesticide Regulation, Director John McCamman wrote that, “These second-generation anticoagulant rodenticides have a long, well-documented history of impacting non-target wildlife, and thus, the Department of Fish and Game recommends revising California regulations to make these materials restricted.”

In its letter, the department cites studies in which 92 percent of raptors collected in San Diego County and 79 percent of federally endangered San Joaquin kit foxes in the Bakersfield area showed residues of anticoagulant rodenticides in their blood. Of 104 mountain lions tested since 2005, 82 had rodenticides in their blood. While the poison may not have killed the animals, DFG called its presence in their bloodstreams a “disturbing indicator of the prevalence of these poisons in our environment.”
Mr. Buck began to look into alternative ways to manage rodents and set out to create rodenticide-free zones, beginning in Bolinas. He approached Wildcare, a wildlife rehabilitation center in San Rafael, which put him in touch with the Hungry Owl Project, or HOP.

Based in San Anselmo, HOP aims to reduce the need for pesticides and rodenticides by encouraging natural predators through conservation of habitat, nest boxes and education. The group began in 2001 by installing owl boxes in vineyards, hoping to control rodents without using pesticides. The group has expanded efforts to include vineyards in Marin, Sonoma and Napa counties, and several hundred owl boxes have also been placed in suburban neighborhoods.  The boxes are effective because they provide otherwise absent living quarters for owls, which must nest in holes or tree cavities that are not always easy to come by.

“We focus on barn owls, because they are not territorial and can easily be attracted to an area,” the program’s director, Alex Godbe, said. “We can easily put up quite a few boxes in a small area to target it.”

Last year, HOP installed six plywood owl boxes outside of the Marin County Civic Center to deal with a rat problem there. Several of the boxes have been occupied by owl families since then, and while some remain vacant, a single owl can eat thousands of rodents a year. Still, Ms. Godbe said that while a healthy owl population might be enough to keep rodents out of a mature vineyard, other venues will likely need to use a more integrated approach.

By taking local polls and educating residents, Mr. Buck has so far persuaded two stores in Bolinas, the hardware store and Bolinas Market, as well as the Stinson Beach Market, to stop carrying rodenticide.  The county has passed a resolution asking all Marin stores to ban the sale of rodenticides, and Mr. Buck says he supports DFG’s request to reclassify rodenticides as a restricted material.

But over at the Point Reyes Building Supply Center, owner Jim Simon is reluctant to take the product off his shelves without a clear and effective alterative in sight. “There’s no law saying we can’t carry it,” Mr. Simon said. “Tell me something that will work just as well, or come up with a better solution that is proven to work. Otherwise the demand will still be there.”