The U.S. Fish and Wildlife Service announced Wednesday that it may add Pacific fishers in three western states to the list of Threatened Species. The increasingly rare member of the weasel family has come under increasing pressure from loss of habitat, as well as from exposure to rat poisons used at illegal marijuana grow sites.
The West Coast population of Pacific fishers (Pekania pennanti) ranges from California's north coast and the Sierra Nevada through the Cascade Range into Oregon and Washington. The carnivorous fishers are rare in the best of times, making them especially vulnerable to population declines caused by human intervention in their habitat.
According to USFWS, one of the biggest threats to the fisher is widespread exposure to anticoagulant rat poisons, which are taking a toll on many other predator species across the U.S.
Several previous attempts since 1990 to get the West Coast population of Pacific fishers listed as Threatened or Endangered eventually ended up in a 2004 ruling by USFWS that the fisher deserved protection, but that it was "precluded" from listing by other, higher-priority species in need of protection sooner.
This is the controversial "warranted but precluded" status that was a subject of a 2011 legal settlement between USFWS and the Center For Biological Diversity in which USFWS agreed to make decisions whether or not to protect more than 750 species that were candidates for protection.
In addition to that legal settlement, USFWS cites increased data on the threat from rodenticides as a reason for the agency's proposal to list the fisher. The majority of fisher carcasses recently assessed by forensics workers show signs of exposure to rodent poisons, the USFWS said in its Federal Register announcement of the potential listing.
Anticoagulant rat poisons are widely used at illegal marijuana grow sites in an attempt to keep wildlife from eating or otherwise damaging the growers' crops. Researcher Mourad Gabriel has described finding grow sites with poison-laced hot dogs left about as bait, posing an obvious threat to carnivorous animals like the fisher.
USFWS has published a YouTube video explaining some of the reasons for its proposal in more detail. In addition to rat poisons, the video cites "vegetation management" as a cause of the fisher's decline. (You can pretty much read that "vegetation management" as logging.)
The announcement starts a year-long decision-making process which will lead to a final decision whether or not to list the fisher. A public comment period on the proposed listing runs until January 5.