Local and national conservation groups today sued the federal government in an attempt to force threatened species protection for Pacific fishers, saying the government chose politics over biology when denying federal listing last spring.

The Ashland-based Klamath-Siskiyou Wildlands Center and others filed suit in U.S. District Court in San Francisco against the U.S. Fish and Wildlife Service, saying the decision not to list flies against the service's previous opinions that the small carnivores deserved Endangered Species Act protection.

The USFWS recommended threatened species status for fishers in 2014, but the agency reversed that decision in April even though the fisher's status has remained largely the same, with isolated populations in scattered areas that include the Klamath and Siskiyou mountains.

"We just want to make sure that science, not politics, is driving decisions about fishers," said KS Wild Executive Director Joseph Vaile.

The suit also claims the USFWS is underplaying the threat that rodenticides in both legal and illegal marijuana grows poses to fishers, which are poisoned when they feed on rodenticide-killed rodents.

"Even with legalizing of marijuana, there are still big illegal grows, and they're finding huge quantities of those rodenticides," Vaile said. "It's something that hasn't been fully vetted by the Service."

A Fish and Wildlife Service spokeswoman in Portland did not immediately return telephone calls seeking comment. 

Joining KS Wild in the suit are the Center for Biological Diversity and the Environmental Protection Information Center. They are represented by Earthjustice.

About the size of large house cats, fishers belong to a family of mammals that includes weasels, mink, martens and otters. They live in low- to mid-elevation forests and require cavities in trees for rearing their young, as well as forest canopies to rest and hide from predators.

The fisher's range was reduced dramatically in the 1800s and early 1900s through trapping, predator and pest control, and changes in forest habitats from logging, fire, urbanization and farming, according to the USFWS' April 14 declaration against listing.

The Siskiyou Mountains population of Pacific fishers is native, while another in the South Cascades is from fishers introduced by private timber owners to prey on porcupines, which damage young trees. Fishers are the only animals known to prey regularly on porcupines, flipping them and attacking their abdomens.

The USFWS estimates anywhere from 1,000 to 4,000 fishers live in Southern Oregon and Northern California, including those in the South Cascades and Siskiyous. The southern Sierra Nevada population is about 300 animals, and more than 100 have been reintroduced in Washington.

"The Siskiyou Mountains still have the most healthy population on the West Coast, but we're talking 4,000 animals," Vaile said. "It's not a big population."

After years of study and lawsuits, the USFWS in October 2014 proposed listing fishers up and down the West Coast as threatened based on threats to its habitat from wildfire, logging and pesticides.

However, the USFWS said in April that while those threats still exist to these small predators, they are not causing significant enough impacts over the fisher's entire range to require a listing.

The Rogue River-Siskiyou National Forest is studying fishers in the forest outside of Ashland as part of the multi-agency Ashland Forest Resiliency Stewardship Project.

— Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.