A peer-reviewed paper released today in the online journal PLoS One documents deaths due to anticoagulant rodenticides in fishers, an elusive forest carnivore in the weasel family. The study shows that a high percentage of fishers tested have been exposed to these rodenticides.
The study was led by UC Davis, and involved researchers from the nonprofit Integral Ecology Research Center, UC Berkeley, United States Forest Service, Wildlife Conservation Society, Hoopa Tribal Forestry, and the California Department of Fish and Game’s Wildlife Investigation Lab.
The research team was surprised by their findings because fishers live in the mature forests of the national forests, national parks, private timberland and tribal community lands – nowhere near urban or agricultural areas where one might expect to find evidence of rodenticide use.
Examination of the areas where exposed fishers lived shows that their habitat overlaps with illegal marijuana farms. Large amounts of rodenticide and other chemicals have been observed around marijuana plants and along plastic irrigation lines that supply the grow sites.
Other species that inhabit the forests and share the same prey as fishers, like martens and spotted owls, and Sierra Nevada red foxes may also be at risk.
The research team hopes to continue this work and examine whether toxicants used at illegal marijuana grow sites on public lands are also indirectly impacting fisher populations and other forest carnivores through prey depletion.