Environmental activists love to harass farmers because, let's face it, protesting farmers is safe. You never see activists protesting the far worse environmental damage done by Mexican cartels raising illegal marijuana. Dead bodies are terrible for fundraising.
But that doesn't mean the damage isn't obvious. A new study has found that the annual rate of poisoning deaths of relatively rare, forest-dwelling fishers (Pekania pennant) rose 233 percent compared to a study in 2012. The toxicants were associated with illegal marijuana farms on public and tribal lands in Northern and Southern California.
Previous studies showed that rat poisons were being found in the tissues of this cat-sized relative of the weasel family when they were in proximity of illegal marijuana cultivation sites in rugged portions of Northern California and the southern Sierra Nevada.
"We know that a 10 percent change in mortality rate is enough to determine whether fishers in California are able to expand their population size or not," says Dr. Craig Thompson, a PSW research wildlife ecologist and one of the study's authors. "Now we know that rodenticide poisoning alone is enough to keep fisher populations suppressed in the state, even without accounting for the fact that low doses of these poisons also cause the animals to be lethargic and susceptible to disease, which in turn increases the potential for other sources of mortality."
A team of researchers from the U.S. Forest Service's Pacific Southwest Research Station, Integral Ecology Research Center, University of California, Davis, University of California, Berkeley, and partner organizations conducted the study from 2007 to 2014 at three research sites - one in Northern California and two in the southern Sierra Nevada. At all locations, researchers captured fishers in box traps - humane enclosed traps - and fitted them with a VHF radio-collar with the goal of collecting information, such as habitat use and survival rate.
Researchers tracked the animals and were able to retrieve the carcasses when data from the collars indicated that an animal had died. They recorded all causes of death, including predation (70 percent), natural disease (16 percent), poisoning (10 percent), vehicular strike (2 percent) and human causes (2 percent). Bobcat (40 percent), mountain lion (38 percent), and coyote (6 percent) were the fisher's primary predators.