Pacific Fisher Denning in Yosemite National Park

A young Pacific fisher, a cousin to the weasel, has been denning in the southern reaches of Yosemite National Park, the first time biologists have been able to confirm such activity in the park.

The occasion is noteworthy because the Pacific fisher is a candidate species for protective listing under the Endangered Species Act. Once flourishing from British Columbia south through Washington and Oregon into the Sierra, the mammals today can be found in just about half their California range, according to park officials. Trapping and low reproductive rates have largely been pointed to as the cause of the fisher's decline, although lately being run over by vehicles has become another concern, they said.

In California, the species is split into two populations: one located near the western California-Oregon border, and the other in the southern Sierra Nevada in California. Yosemite represents the northern boundary of the small and isolated southern Sierra Nevada population, which is estimated to be between 125 to 250 adults, according to park officials.

The female that was located in Yosemite recently was captured back in 2009 in the Sierra National Forest just south of the park and fitted with a tracking device.

After remaining near her capture site for almost a full year, she moved northward toward Yosemite. This female fisher recently moved her kits (young) from their den in Sierra National Forest where they were born, to a den in the southern portion of Yosemite National Park. This is typical behavior for a female fisher with newborn kits. The female will likely move her kits one to two more times to different dens during the next month.

To promote continued fisher recovery, partnerships have developed between the NPS, the Yosemite Conservancy, U.C. Berkeley, the U.S. Forest Service, the U.S. Fish and Wildlife Service, and the California Department of Fish and Game.

This important recovery work has been made possible with support from Yosemite Conservancy, the Wilderness Society, and the Aspenwood Foundation.

Comments

While backpacking, I saw a Fisher in Yosemite about 35 years ago. I was teaching in the San Jose State University biology department at the time and knew what a Fisher was and looked like. My guess is they've been in the Yosemite backcountry before, and since, my spotting.