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Rat poison used by Cannabis growers may be killing owls.

By Madeline Shannon of the Daily Courier

A recent study by researchers at the University of California, Davis found that nearly half of 94 deceased owls collected in Northern California died a gruesome, painful death.

The culprit? Rat poison. And marijuana.

The study, published in the academic journal Avian Conservation and Ecology in conjunction with the California Academy of Sciences, is the first published account of anticoagulant rodenticide found in both barred owls and spotted owls.

The owls, the researchers suspect, are ingesting poison picked up from prey. The source of the poison is believed to be pot farms.

Given that both species of owls are indigenous to this area and that there are more than 5,000 legal marijuana farms and grow sites in Josephine and Jackson counties — the most in Oregon — it raises the question: Is this an issue here?

It's hard to say, apparently.

Scholars involved with the northern California study and local wildlife officials say it very well could be. But with no hard numbers to prove owls in Oregon are dying from rat poison picked up on marijuana farms, it's hard to tie cause and effect.

"We don't always get the owls tested," said Dan Ethridge, assistant district wildlife biologist at the Oregon Department of Fish and Wildlife, of the owls his office picks up. "It's a big expense, having them tested, so there could be more out there that were poisoned. It's not necessarily the first thing we go to."

Wildlife biologists often conclude that an owl was killed by being hit by a car or ingesting some type of poison, but without actually testing the bird's corpse, it's nearly impossible to determine the cause of death.




"It's difficult to tell," Ethridge said. "It's not something we have a good handle on in our area yet."

The study conducted by UC Davis included owls found in Humboldt, Mendocino and Del Norte counties, but because barred owls and spotted owls are also indigenous to the Pacific Northwest, local officials say the problem could be cause for concern here, too.

"We're in the early stages of this," Ethridge said. "It's potentially a threat and it's becoming more and more discussed, but this early on, it's hard to get any good, hard data about what's going on."

However, according to the authors of the Northern California study, there is evidence showing barred owls, specifically, are ingesting rat poison in Oregon.

"We do have evidence that Oregon barred owls have been exposed to rodenticides," said Mourad Gabriel, lead author on the northern California study. "It's not known how extensive it is in Oregon."

Despite scientists finding links between the barred owl in Oregon and rat poison, local marijuana farmers doubt owls are ingesting poisoned rats in this area. One Josephine County grower attributes that to organic practices that don't call for substances like rat poison.

"That practice isn't done here in the Williams Valley," said Shayne Christen, owner of Stick Pony Farms in Williams. "We've tried to work within the law. One of our biggest bragging points is that we don't use any pesticides or inorganic fertilizers."

Hence, Christen says, the lack of dead owls in the area.

"I haven't seen any of them dying," Christen said. "They're pretty active here. We've got three in the neighborhood."

According to the U.C. Davis study, rat poison doesn't just make owls sick. Anticoagulant rodenticides — rat poison — inhibits an owl's ability to recycle vitamin K, which results in clotting, coagulation and ultimately uncontrollable internal bleeding.

Fortunately, few cannabis producers are using anything non-organic, according Christen. That is hard to prove, however, since no one in the local marijuana industry is actually keeping track of who is using what to control rats.

"Most of the problem has taken place in California," Christen said.

The methods marijuana growers in the area are using, Christen added, are organic and approved by the Organic Materials Review Institute.

When asked what he and his colleagues in the area use to deter smaller critters like rats from eating the crop, there's only one thing Christen uses.

"Dogs," he said.

Gabriel and his colleagues are now studying owls in the Pacific Northwest. That study hasn't been published yet, but so far, Gabriel is finding the region's owls are dying from ingesting rat poison, as well.

He's just not sure where, exactly.

"We want to continue this type of research to determine how extensive it is through to Pacific Northwest," Gabriel said. "We can then have concentrated, focused efforts on conservation in areas where it is actually present, without having to extend efforts beyond that range."

Earlier Event: February 8
Cannabis growers cautiously upbeat