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On a cool day in November, John Knox found an unpleasant surprise in his San Francisco yard.

“I’m sad to report that I found a really beautiful but very dead barn owl yesterday in our garden,” wrote Knox, Earth Island’s Executive Director Emeritus, in an email to his neighbors.

“With no obvious other possible cause of death, one must suspect the current generation of rodenticides/rat poisons since the poisons are deadly not only to rodents but also to raptors, other wildlife, house pets, etc., who might try to eat an affected rodent.”

Rodenticide Poisoning

Knox sent the owl to the California Department of Fish and Wildlife and received this report back in December: “Gross necropsy revealed coagulopathy, and chemical analysis determined that the owl’s liver contained three second-generation anticoagulant rodenticides, two in potentially lethal concentrations. Anticoagulant rodenticide intoxication is identified as the cause of death.”

Deaths like these happen all too often in California.

Affected wildlife includes many species of owls and hawks, vultures, bobcats, mountain lions, foxes — anything that preys on rodents.

Perils of Rat Poison

Anticoagulant rat poisons cause rats and mice to bleed to death internally.

The poisons bioaccumulate in the wildlife that preys on rodents, and they, too, become sickened or die from “rodenticide intoxication.”

Although second-generation anticoagulants are designed to kill in one feeding, both first and second-generation anticoagulants cause bioaccumulation and death in non-target wildlife.

In 2014, the state performed a reevaluation of these products and banned second-generation anticoagulants from consumer shelves.

But in a giant loophole, it allowed the pest control industry to continue to use them.

Since the ban, there has been no decrease in the number of wildlife poisonings in California, according to the data collected by Fish and Wildlife.

Raptors Are The Solution Give Voice to Wildlife

That’s why last summer, Raptors Are The Solution (RATS) filed a lawsuit against the California Department of Pesticide Regulation (DPR).

The suit challenges the state’s continued registration of these products without fully evaluating their impacts on non-target wildlife, without evaluating new science about their impacts, and without evaluating their cumulative impacts.

Exposure to first generation anticoagulant rat poisons is linked to diseases that impact the immune systems of non-target animals like lynx, coyote, and mountain lions. Photo by Joe Galkowski

Impact of Rodenticide on Wildlife

Prior to filing the lawsuit, RATS and Project Coyote, another Earth Island project, submitted a dozen new scientific studies about the impacts of these rodenticides on non-target wildlife, requesting that DPR reevaluate them.

Those studies showed that over 70 percent of Northern spotted owls and 40 percent of barred owls are contaminated with rodenticides; that ferruginous hawks preferentially prey on poisoned rodents; and that exposure to first-generation anticoagulants is linked to diseases that impact the immune systems of animals like coyotes and mountain lions.

“The persistence of these poisons in the environment and their impact on non-target wildlife is irrefutable. From coyotes to bobcats to imperiled fisher and kit foxes, we know that rodenticides can weaken immune systems, making predators susceptible to diseases like mange that ultimately can kill them,” says Camilla Fox, founder and executive director of Project Coyote.

Reevaluating Second-Generation Anticoagulants

In November, DPR announced a proposed decision to reevaluate second-generation anticoagulants.

While RATS, Project Coyote, and our many coalition members support that reevaluation, we believe it must also include first-generation anticoagulants.

RATS has been tackling this problem since it became an Earth Island project in 2013.

We’ve educated millions of people about the dangers of anticoagulant rat poisons through billboards and ads on public transit.

We’ve developed extensive educational materials, many of which have been translated and disseminated throughout the world.

And we will continue to push for reevaluation of all dangerous rodenticides in California and beyond.

— Lisa Owens Viani

Learn more about the Earth Island Project at: www.raptorsarethesolution.org

This story originally appeared in Earth Island Journal