Four rescued fisher ( Martes pennanti) kits were released recently north of the Merced River in Yosemite National Park. This historic reintroduction was a cooperative effort between the National Park Service, U.S. Forest Service Pacific Southwest Research Station (PSW), Fresno-Chaffee Zoo, and the Fresno Wildlife Rehabilitation Foundation. The reintroduction aims to increase the long-term viability of the declining fisher population by expanding its population to the northern part of Yosemite National Park.
The kits, two sets of siblings, were rescued south of the park on U.S. Forest Service land after two radio-collared female fishers were killed by predators. The kits were rescued by PSW researchers Craig Thompson and Laura Van Vranken.
Estimated to be approximately eight weeks old, the kits were taken to the Fresno-Chaffee Zoo to be cared for until they could eat solid food. They were then moved to an outdoor facility near Oakhurst run by the Fresno Wildlife Rehabilitation Foundation where they have since grown and learned to hunt live prey.
The release of these orphan kits, now approximately six months old, back into the wild is part of a four-year effort to reintroduce fishers north of the Merced River in Yosemite National Park. Historic records show that fishers once occupied this area but trapping and logging in the late 1800s and early 1900s likely led to their local extinction. Despite over 70 years of protection, fishers have failed to successfully recolonize the area.
Biologists hope that human-assisted migration north of Yosemite Valley and across the Merced River barrier may help increase the long term viability of the population by expanding its distribution. National Park Service and Forest Service biologists will work together to monitor these four kits.
If they survive at rates similar to other juvenile fishers, the population will be augmented in the following years with additional orphans that would have otherwise died if they had not been rescued by researchers.
The small, isolated population of fishers in the southern Sierra Nevada is listed as threatened by the state and is under consideration for federal listing. This is due to fire, habitat loss, and other environmental threats.
This project was made possible with generous support from Yosemite Conservancy. Other partners include the U.S. Forest Service, U. S. Forest Service Pacific Southwest Research Station, Central Sierra Environmental Resource Center, Fresno-Chaffee Zoo, and the Fresno Wildlife Rehabilitation Foundation.