Illegal Marijuana Cultivation Is 'Silently Killing' Threatened Weasels

Illegal marijuana cultivation in California fields is killing the cat-sized relatives of weasels found the Pacific Northwest, known as the “fisher.” According to a latest research, a number of fisher deaths from pesticides have increased by over 200 percent since 2012.

During the study, a team of researchers studied the cause behind the increased fisher mortality around the illicit marijuana cultivation sites in California. The researchers found that an increased number of fishers were dying because of their exposure to the rat poison coming from the fields.

The researchers classify the rat poison as an “emerging threat” to the fisher, as it is something which is generally not found in their original remote forest habitat. The researchers based their conclusion on the study of the corpses of 150 fishers recovered from California between 2007 and 2014.

As detailed in the journal PLOS ONE, the team discovered that predation by other animals, such as coyotes and bobcats, accounted for nearly 70 percent of the deaths. Nearly 16 percent of the fisher had died because of the natural diseases, while 10 percent were killed by rodenticide poisoning.

The fact that shocked the researchers the most is that nearly 85 percent of the animals were being exposed to the rat poison. That is, the poison was present in the body of the animals, even if they were eventually killed by a predator. The researchers find the condition as worrisome as the animals are still recovering from the decline in the area.

"We're showing that it's not getting better," said lead author Mourad Gabriel of the Integral Ecology Research Center at Blue Lake, Calif. "Fishers are the flagship species. We have to think of so many species, like Sierra Nevada red foxes, spotted owls, martens -- they all are potentially at risk. This is essentially going to get worse unless we do something to rectify this threat."