Fresno Bee Newsroom Blog

More evidence linking poison at pot farms to wildlife deaths

A scarce mountain animal called the fisher — a cat-sized relative of the weasel — is dying from rat poison used in illegal marijuana fields along the southern Sierra Nevada, researchers say in a new study released last week.

The study bolsters last year’s research from scientists at University of California, Davis, who said it appeared the rat poison found in the bodies of dead fishers came from the hidden pot farms.

The latest study was done by a team from UC Davis, the U.S. Forest Service’s Pacific Southwest Research Station, UC Berkeley and the Integral Ecology Research Center in Humboldt County.  It was published in the journal Conservation Letters.

There are only 46 adult female fishers left in this region, researchers said. The animal is a candidate for protection under the Endangered Species Act for both California and the federal government.

In the study published last week, scientists reported on the amount of poisons found at more than 300 illegal plots and compared the locations of these sites with the home ranges and survival of the 46 female fishers.

The evidence leads researchers to believe the illegal pot farms, not rural developments or agriculture, were the problem. The fishers in the study were radio-tracked. Many were not observed into rural, urban or agricultural areas where rodenticides are often used legally.

Some fishers have died from eating the flavored poison or eating prey that had recently ingested the poisons. But the exposure may also weaken or confuse healty fishers, resulting in death from other causes, such as predation or traffic.

Scientists add that other animals with dwindling populations might be affected too. The species include the wolverine, marten, great gray owl, California spotted owl and Sierra Nevada red fox.