The furry, dark brown creatures hesitated at first and then shot out of their plywood cages and bounded into the forest near the hamlet of Stirling City.
It was the latest triumph in a remarkable campaign to bring back a long-lost predator known as the Pacific fisher to the northern Sierra Nevada.
The four stubby-legged mammals were released by California Department of Fish and Game biologists as part of an innovative effort to reintroduce the weasel family species to a region they were driven out of 100 years ago.
Three female fishers and one male were exposed to the dreaded sunshine - they're nocturnal - and gently prodded out of the open doors of their boxes onto Sierra Pacific Industries timberland in Butte County, bringing to 39 the total number of fishers moved into the area over the past three years. That's one less than the 40 fishers the reintroduction plan calls for.
"This is a milestone for us," said Richard Callas, a senior environmental scientist for the Department of Fish and Game, which is working with the U.S. Fish and Wildlife Service and North Carolina State University researchers. "We will continue to monitor them for the next three or four years. We want to see how they are using the land, what habitats are important, how they are faring and how they migrate to other areas."
The fisher program is the result of a highly unusual partnership with Sierra Pacific, one of the country's largest timber companies and the state's largest private landowner.
The idea was first broached in 2004, when Sierra Pacific offered Fish and Game officials five large tracts of land where fishers historically occurred but no longer existed. The department evaluated each plot and determined that a 168,000-acre tract of timberland near Stirling City, near Paradise Ridge, was the most suitable place to reintroduce the species.
Pacific fishers are cantankerous animals with lush fur, long slender bodies and short legs. They are related to martens, wolverines and weasels. The females are half the size of the males, which weigh about 10 pounds. They mate in the spring, but otherwise have little to do with one another.
Fishers prefer dense old-growth forests where they can hunt in the trees and den in hollowed-out areas up high. They hunt squirrels, chipmunks and mice, and often scavenge carcasses and also eat roots and plant material. They are one of the few animals that kill and eat porcupines, going for the throat and then turning the spiny beasts over to feed on the stomach.
Curiously, though, fishers don't eat fish. It is believed they were named by early settlers who thought they looked like European polecats, also known in French as fiche or fitchet. The Dutch equivalent, visse, means "nasty."
The small, feisty mammals once ranged throughout the Sierra, Klamath, Cascade and Coastal ranges, but hunting, logging, development and habitat loss drastically reduced their numbers. In the early 20th century, fisher pelts, called North American sable, fetched hundreds of dollars.
By 1946, when fur trapping of fishers was banned in California, the population had been reduced and was living in an area that was less than half of its former range. Fishers, for the most part, were wiped out in Oregon and Washington. Only two populations now exist in the state; on the border between the Klamath and coastal mountain ranges and the other in the southern Sierra, near Yosemite. Nobody knows exactly how many are left - they are notoriously difficult research subjects because they have wide ranges, leave few signs and assiduously avoid human contact - but recent estimates had them down to 850.