Here’s Why Owls are Dying Near Marijuana Farms

UC Davis study blames endangered owl deaths on unpermitted cannabis growing operations. They predict the trend will escalate as the recreational weed market takes off in California.

New research done by UC Davis reveals that several species, including the northern spotted owls, are threatened by rat poison. This was caused by the thousands of “unpermitted private marijuana grow sites”.

The study was published in the journal Avian Conservation and Ecology. It focused on owls in Northern California’s Humboldt, Mendocino and Del Norte counties.

Scientists tested the owls

Owls are threatened by marijuana growth
Northern Spotted Owl flies after a mouse to catch in Deschutes National Park. via Press Democrat

The test showed the poison was contaminating the owls’ primary food source — mice and rats. Scientists tested 10 northern spotted owls found dead in the region. Seven of the owls tested positive for rat poison. Further investigation found pot farmers use this to keep rodents away from their irrigation systems and crops.

Consequently, the species was listed as “threatened” under federal and state endangered species act. in addition, barred owls compete for the same space and resources as their spotted kin. As a result, they are also being exposed to the same poison from their communal prey.

Of the 84 dead barred owls the researchers collected, roughly 40 percent tested positive for the substance. It impedes the body’s ability to clot blood and can result in unchecked internal bleeding. In addition, private, illegal or otherwise unpermitted marijuana grow sites often share with designated critical habitats for northern spotted owls.

“Spotted owls are inclined to feed along forest edges. Because grow sites break apart these forest landscapes, they are likely the source points for exposure,” said lead study author Mourad Gabriel, of UC Davis.

Legalization could make it worse for owls

Mourad Gabriel, a research faculty member of UC Davis’ Wildlife Health Center, led research connecting rat poison from unpermitted, private marijuana to the deaths of northern spotted owls and barred owls in northwest California. via K5 News

Also, with the rollout of Proposition 64 in California, it may increase the number of cultivation sites. For that reason, this could “exacerbate the problem,” researchers said. Only a few of the 4,500 to 15,000 private cultivation sites actually operate with regulatory oversight.

“There are thousands of unpermitted grows and only a handful of biologists that regulate that for multiple counties. We’re deeply concerned that there aren’t sufficient conservation protective measures in place,” Gabriel said in the statement. “Furthermore, if no one is investigating the level at which private marijuana cultivators are placing chemicals out there, the fragmented forest landscapes created by these sites can serve as source points of exposure for owls and other wildlife.”

In addition, the results of the study support further investigation into the fragile environment that holds the natural world together.

“Access to these owl specimens allows us to explore the health of the entire regional forest system,” said Jack Dumbacher, curator of ornithology and mammalogy at the California Academy of Sciences, where the necropsies were conducted.

“We’re using our collections to build a concrete scientific case for increased forest monitoring and species protection before it’s too late to intervene.”