Pot Farmers Killing Rare Wildlife


Rat poison is killing fishers, a rare carnivore, in some of the most remote forests of California—and pot growers are probably to blame.

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A research team led by veterinary scientists at the University of California, Davis, discovered commercial rodenticide in dead fishers found in and around Yosemite National Park and near Redwood National Park. Of the 58 fisher carcasses they analyzed, 79 percent of them had been exposed to anticoagulant rodenticides, which can lead to uncontrollable bleeding.

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The fishers either ate poisoned rodents or consumed the poisons directly, drawn by the bacon, cheese and peanut butter “flavorizers” that manufacturers add to them, the team reports in the July 13 edition of the journal PLoS ONE.

You might expect national parks to be a safe place for wildlife. So where the heck did the poison come from? The research team, which concludes that illegal marijuana farms are the likely source, do not make their accusation lightly.

Death by rat poison is typical for wildlife living near urban and agricultural areas. But these dead fishers, many of which had been radio-tracked throughout their lives, did not wander anywhere near either type of environment, lead author Mourad Gabriel explained in a press release. (Gabriel is a UC Davis Veterinary Genetics Laboratory researcher and president of the Integral Ecology Research Center.)

The fishers’ habitat did overlap with illegal marijuana farms, however. The study notes that in 2008 alone, law enforcement officials removed more than 3.6 million marijuana plants from federal and state public lands in California, including state and national parks.

In one recent example, agents confiscated more than 2,000 marijuana plants less than 7.5 miles from one of the study areas. They also found piles of bright green rodenticide pellets around the marijuana plants and along plastic irrigation lines (right).

Another clue is that the fisher deaths occurred between mid-April to mid-May, the optimal time for planting young marijuana plants outdoors—and the time when seedlings are especially vulnerable to pests.

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Of course the hullabaloo is not just about the fishers, which have been declared a candidate species for listing under the federal Endangered Species Act. Plenty of other forest denizens — including martens, spotted owls and Sierra Nevada red foxes — are also at risk of poisoning. Not to mention the rodents!


Fisher, a rare forest carnivore and member of the weasel family. (UC Davis)

Illegal marijuana plants and bright green pellets of anticoagulant rodenticide. (UC Davis)

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