June 27, 2013
Pot Farmers Are Killing Animals
Lee Rannals for redOrbit.com — Your Universe Online
Marijuana farmers are killing off a native mammal in southern Sierra Nevada with rat poison, according to a new study.
A previous study found that rodenticides were being found in the tissues of fishers, which are weasel-like creatures that live in southern Sierra Nevada. The researchers from this study believed that the most likely source of the poisons was illegal marijuana growers, and the latest research has confirmed the link.
Scientists found poisons at over 300 illegal plots and compared the location of these sites with the home ranges and survival of 46 adult female fishers.
The scientists were able to determine that illegal marijuana farms were likely the source of the poison because the fishers in this study were radio-tracked and many of them were not observed venturing into rural, urban or agricultural areas, where these rodenticides are used illegally.
Illegal marijuana grow farms are widespread in this area, and many farmers use rodenticides and insecticides to get rid of the animals and insects coming around their crops. The researchers said the amount and variety of poisons found at the illegal marijuana plots is a new threat.
PSW wildlife biologist Dr. Kathryn Purcell said exposure of wildlife to these pesticides is not uncommon, but this is a "fundamentally different scenario."
"In marijuana cultivation sites, regulations regarding proper use of pesticides are completely ignored and multiple compounds are used to target any and all threats to the crop, including compounds illegal in the U.S.," Purcell says.
Some fishers are dying from directly consuming the rodenticides, while others are dying from indirect causes. Exposure to rodenticides in low doses results in slower reflexes, reduced ability to heal from wounds and neurological impairment, which makes them more susceptible to becoming prey or road kill.
"By increasing the number of animals that die from supposedly natural causes, these pesticides may be tipping the balance of recovery for fishers" says Dr. Craig Thompson, a PSW wildlife ecologist and the study's lead author.
Fishers may not be the only animals being affected by these illegal farms. Other species already facing declining populations could also be exposed to these poisions, such as wolverine, marten, great gray owl, California spotted owl, and Sierra Nevada red fox.
A study in January showed that the fisher population in the southern Sierra Nevada region has been stable, despite the animals dwindling in numbers throughout the West Coast. However, the impact the illegal marijuana farms have on this animal is not fully understood and could potentially bring those numbers in Sierra Nevada back down.