Marijuana Farms Are Poisoning This Mink-Like Animal With Rodenticide

The fisher, an animal in the weasel family about the size of a house cat, is threatened by rat poison used on pot farms.

As the market for legal weed has blossomed in some states, so too has the use of rat poison on pot farms deep in the western woods, to keep rodents away from the aromatic plants. These are the same woods where a rare cat-sized mammal called the fisher lives in the cavities of trees and feeds on smaller animals—animals whose little bodies are full of the pot farmer's rodenticide.

The fisher, whose numbers and range are already precariously low due to two centuries of trapping and logging, has been relegated to the same patches of public land in California, Oregon and Washington where illegal pot farming has taken hold. The threat of rodenticide has become widespread enough for the U.S. Fish and Wildlife Service to announce Monday a proposal to add the fisher to the national list of endangered species.

Fisher 3
The fisher is a forest-dwelling, omnivorous creature. They eat a wide variety of small animals are one of the few predators able to hunt porcupine. Bethany Weeks for USFWS Pacific Southwest Region

When biologists assess the grow sites after raids, they often find packaging for large quantities of potent commercial rodenticides and other toxins, which are being used without regulation and in large quantities at grow sites. Rats and squirrels can survive three to seven days after eating the rodenticide, so the doomed animals roam around, falling prey to the fisher. One or two poisoned meals won't kill a fisher, explains Mourad Gabriel, executive director of the Integral Ecology Research Center. But eating like that regularly will.

"It's filling up slowly with these anti-coagulant rodenticides," Gabriel says. Without immediate human intervention, like a vitamin K injection, "that fisher is going to succumb to the exposure levels and die."

A study published in 2012 in the journal PLOS One found rat poison in the bloodstream of 79 percent of fishers they tested. More recent studies have put the number above 80 percent.

Illegal grow site
Biologists assess illegal grow site USFWS Pacific Southwest Region

Environmental groups have pushed for years for protection for the fisher under the Endangered Species Act. Groups like the Center for Biological Diversity see its listing as key to the fight against plans to increase logging of public forest lands known as the "O&C lands" in western Oregon. Logging is also a significant stress driving down fisher populations, according to the Fish and Wildlife Service.

"In addition to Endangered Species Act protection, the strong protections provided by the Northwest Forest Plan for old forest habitat need to be maintained, including on O&C lands," Noah Greenwald, endangered species director at the Center for Biological Diversity, said in a statement following the listing announcement. "And the dangerous rodenticides being used by illegal marijuana growers that have poisoned fishers need to be completely banned."

The threat to the fisher is the latest of a string of recent news of ecosystem damage caused by marijuana farms. Streams are frequently diverted, without permit, to irrigate marijuana crops, using copious amounts of freshwater and posing a threat to the water supply in drought-ravaged states like California. In other waters, fertilizer and pesticide runoff is sparking blooms of toxic blue-green algae.

Last summer, 24 tributaries of California's Eel River went dry. Each tributary was being used to irrigate pot farms, California Department of Fish and Wildlife biologist Scott Bauer told NPR. The tributaries once hosted enormous spawning runs of Chinook salmon, but the fish there nearly vanished last summer, which will likely hurt salmon populations for several years.