In Effort to Help Wildlife, California Bans Household Rat Poisons

This week's ruling on rat poisons may be good news for wildlife like the Pacific fisher. | Photo: washuugenius/Flickr/Creative Commons License

The California agency responsible for regulating pesticide use in the state has banned household use of rodent poisons that have shown to cause serious damage to the state's wildlife.

On Tuesday, the state's Department of Pesticide Regulation (DPR) ruled that it would ban most retail sales of anticoagulant rat poisons as of July 1, limiting their use to trained professional exterminators.

As we've reported here extensively in the past, anticoagulant rat poisons such as brodifacoum have been taking a terrible toll on California's wildlife, which ingest the chemicals when they eat rodents or other animals that have consumed commercial rat poisons.

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"This is a practical sensible regulation that goes a long way to protecting our wildlife," said DPR director Brian Leahy to the San Jose Mercury News.

Environmental activists have been attempting to get anticoagulant rat poisons banned or restricted at the federal level for years. In 2008, the U.S. Environmental Protection Agency issued regulations substantially similar to those announced this week by the DPR, but those regulations were delayed by a lawsuit from rodenticide manufacturers.

Most commercial rat poisons use the anticoagulant brodifacoum as an active ingredient: when ingested, the poison causes internal bleeding, which usually kills the animal over a period of several agonizing hours or even days. Because the animals targeted by the poison don't associate the bait with their discomfort, they can eat several times the dose needed to kill them. Brodifacum breaks down only very slowly in a living organism, meaning that when a predator finds a rodent that's been poisoned and eats it, it ingests essentially the entire amount of poison eaten by its meal.

Household, industrial, and illegal use of rat poisons have been implicated in fatal illnesses in a wide range of California wildlife species. Rat poison use by illegal pot growers on public lands has contributed to a number of deaths by poisoning of the Pacific Fisher, a picturesque and nearly fearless weasel about the size of a housecat that lives in forested mountains in the northern half of the state. Even when direct poisoning isn't an issue, rat poison can cause other problems for wild animals. Bobcats, for example, seem less susceptible to brodifacoum's anticoagulant properties than do other predators, but their exposure to the chemicals has been linked to increased fatalities from chronic mange.

While restricting anticoagulant rat poisons' use to professional pesticide applicators will likely reduce wildlife exposure by a significant amount, it's likely that large amounts of the rodenticides will still be available in bulk at agricultural supply stores and pesticide wholesalers, raising the possibility that illegal use in the state's wildlands will continue unabated. At least one wildlife advocacy group that's been working on the issue will continue to push for a more complete ban. On the Facebook page of the group Raptors Are The Solution (RATS), a post linking to the San Jose Mercury News story said "Now to tackle the pest control companies!"

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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