A captured fisher is released after examination, part of the Hoopa Valley Tribe’s longstanding efforts to monitor the culturally important species.Elizabeth Miller/Undark
On a sunny November morning, Anthony Colegrove parked his work truck on the side of a road in northern California’s Klamath Mountains and began creating a mobile laboratory. He pulled down the truck’s tailgate, popped open a tackle box filled with syringes and other supplies, and pulled out a clipboard. Meanwhile, a weasel-like animal called a fisher waited nearby, making glottal noises inside a wire trap.
Colegrove is a field technician with the Hoopa Valley Tribe’s wildlife division. He and a colleague, Holly Horan, coaxed the squirming fisher out of the trap and into a metal cone that restrained the mammal while Colegrove injected a sedative into its rump. “She’s out,” Colegrove said, watching the fisher slump.
Colegrove and Horan then commenced an exhaustive examination of the sedated mammal, taking her temperature, swabbing her eyes and nose, drawing blood, and examining the small pale hooks of her claws and her gleaming teeth. Additionally, Colegrove noted and photographed each tuft of pale fur, a dollop of cream on an otherwise coffee and cinnamon pelt.
The young fisher had been trapped before, as evidenced by a microchip embedded below her skin. The information collected by Colegrove and Horan would add to a larger pool of data, offering insights into the life of this one fisher and into the larger population of fishers around the town of Hoopa and beyond. “When we do do stuff, we go above and beyond what everybody else is doing,” Colegrove said.
Tribal wildlife technicians have been capturing and studying fishers since 2005, keeping an eye on a species that is both culturally significant and rare. As a result, the Hoopa Valley Tribe’s wildlife division maintains some of the longest and most detailed documentation of fishers in North America. Their data have helped characterize fisher behavior, aided in estimating their population size, and unveiled troubles brewing for forests and other wildlife. The tribe’s work illustrates how Indigenous-led science can support conservation efforts at a time when Congress is considering increasing its funding for tribes to conduct wildlife research.
Fishers in the region can grow to nearly three feet in length and weigh up to 12 pounds. They are agile enough to spring from tree to tree—and to flip porcupines onto their backs, exposing the soft bellies for attack. After extensive fur-trapping and logging swept through the West from the early 1800s to 1900s, fisher numbers dwindled in much of their historic range across the northern United States.
“They need these big trees, particularly to get up off the forest floor to escape predators, to consume prey,” explained Sean Matthews, who worked with the Hoopa Valley Tribe from 2004 to 2008 and continues to study fishers at Oregon State University. On sunny yet cold winter days, Matthews said, fishers also use the trees to stay warm. “You’ll see them sprawled out on a limb somewhere, just sunbathing.”
The Hoopa Valley Tribe became one of the first self-governing tribes in 1988, as part of a policy shift that allows tribes to retake control from the federal government of the programs that serve their citizens and manage resources on tribal lands. More than 370 tribes have since assumed control of programs overseeing education, health care, transportation, and economic activity—a shift generally seen as better meeting the needs and priorities of tribal members.
As the tribe became responsible for oversight of the timber industry on more than 140 square miles of land, the tribal Forestry Department hired Mark Higley, a wildlife biologist, to help draft a forest management plan and monitor for spotted owls, which had recently joined the Endangered Species List, requiring loggers to steer around them. Soon, Higley saw that fishers were also potentially threatened and culturally significant, so he brought this to the tribal leaders’ attention and began tracking these animals, too.
Tribal members keep ancestral villages of cedar plank houses, known as xonta in the Hupa language, along the Trinity River, visiting them for ceremonies and dances in which fishers are revered. In traditional regalia, a fisher’s fur drapes over a shoulder and the animals’ long, narrow pelts serve as arrow quivers. This coming summer, Colegrove, a tribal member, expects to celebrate the birth of his first child with a dance in which a fisher is called upon to help chase away bad energies. He’s cautious about how much detail he shares publicly, but says tribal elders have long told him fishers are powerful.
When the Hupa began managing their own forests, the tribe reduced the amount of acreage that could be clear-cut at a given time. Each logging project was limited to about 10 acres, and loggers were required to leave clusters of large trees standing. At the time, the available science suggested that fishers could only survive in old growth forests. Higley brought this to the tribe’s attention and was asked to monitor whether a local fisher population might be able to live among the remaining stands.
The answer, it turns out, is yes. Last November, the wildlife biologist stood in an area that had been logged soon after the Hupa took over. He pulled up a GPS map on his phone that showed nearby den sites. Fishers, he said, are drawn to mature tan oaks with rotten cavities in the trunk, just big enough to accommodate a female of the species.
Over the years, Higley and outside researchers have employed a variety of sometimes novel approaches. For example, Higley invited a biologist at nearby Humboldt State University to come to the Hoopa Valley and record fisher prints using “track plates,” a monitoring strategy in which animals walk into a box, stepping first through soot, then onto an adhesive surface that records their footprints. Higley’s office still holds boxes of papers with the five-pad imprint amid dark scattershot loose soot.
With males roughly twice as big as females, researchers could often tell a male from a female track, but not much more than that—and both Higley and the professor wanted more detail. So, they ear-tagged the fishers and started installing cameras with the track plates, sometimes photographing the mammals with their teeth wrapped around a hunk of bait. Research that followed asked and answered a series of census-esque questions about fishers: Where do you live? For how long? How many kids do you have? Is dad still around?
Detailed physical reviews, such as those conducted by Colegrove and Horan, also help answer these questions. (It doesn’t hurt that some fishers are “trap-happy”—prone to falling for bait and getting captured—a characteristic that allows the tribal Forestry Department to monitor these individuals over several years.) Wildlife staff have also used radio collars to study how far fishers wander, and staff have climbed rotting trees to find and microchip kits still in their dens.
When the microchipped kits were recaptured as adults, researchers were able to estimate how far the fishers had traveled from their place of birth. That data showed females tended to set up what’s called a home range adjacent to or overlapping with their mother’s, while males left their mother’s territory almost as soon as they became independent.
This research points to a dilemma for fishers’ recovery. Fishers won’t recolonize their former territory unless their current range becomes so crowded that females feel compelled to spread out from their mothers in search of resources. Absent this crowding, Higley said, “the males are going to run out into Timbuktu” and then not find any mates. It’s entirely possible that many stretches of the Pacific Northwest long emptied of fishers could now support the mammals, but it could be a long time before any fishers are prompted to move there. (Wildlife managers outside of the Hoopa Valley sometimes translocate the mammals—for example, from British Columbia to the Olympic Peninsula in Washington.)
These data and insights collected by the Hoopa Valley Tribe were eventually used by the state of California to estimate the region’s total population of fishers, said Brett Furnas, an ecologist with the California Department of Fish and Wildlife. In a 2017 paper, he and his colleagues estimated 3,200 fishers along the Pacific Coast, or roughly six per 100 square kilometers, but it’s an estimate impaired by much rougher numbers from other areas.
“If a lot of other people were collecting as much data as well as the Hoopa, then we’d have a better model,” he said
In addition to their cultural value, fishers can also provide clues about the health of the broader ecosystem, said Greta Wengert, executive director of the Integral Ecology Research Center, which has been working with the Hoopa Valley Tribe for nearly 20 years. In 2009, Wengert and Mourad Gabriel, who was then co-leading the Integral Ecology Research Center, dissected a fisher that had been found dead in the forest. The animal’s lungs and intestines were full of blood, but there was no sign of an injury. A toxicological test identified the presence of a blood thinner used as a rodenticide. The most likely source of the toxicant? Cannabis cultivation.
To deter rats, cannabis growers in California and southern Oregon place rodenticide around young marijuana plants and along plastic irrigation lines. Fishers can eat the poisoned rats or ingest the rodenticide directly—either way, swallowing enough blood thinner triggers internal bleeding and death.
Wildlife division staff began following law enforcement officers to these grow sites. At one site, Higley found a fisher still foaming at the mouth. An autopsy later revealed pieces of a hot dog laced with poison in the animal’s throat and stomach, suggesting it had died mid-swallow. The tribe knew illegal cannabis operations were out there on public land, Higley said. But until Wengert and Gabriel’s finding, no one had looked for poison in living fishers.
The tribe’s fisher data offered these outside researchers an opportunity to look back in time. Wildlife technicians had extensively sampled their anesthetized fishers and collected tissue from deceased fishers, including taking liver samples. So Wengert and Gabriel set about reviewing those samples. They found fishers had been living with non-lethal levels of rodenticide exposure for years. The researchers then assessed how widespread the problem had become, and found that poison had reached 46 of 58 fishers, or 79 percent; it was threatening, especially, some of the more isolated populations, Gabriel and Wengert wrote in a paper published in PLoS One.
The Hoopa Valley Tribe’s wildlife staff were the first to collect data on this scale, Gabriel said. When other wildlife researchers saw how useful the data turned out to be, they “started replicating, mimicking the Hoopa project.”
But the work faces ongoing struggles for funding. Most of the financial support comes through the U.S. Fish and Wildlife Service’s Tribal Wildlife Grants program, a competitive grants program capped at $200,000. The Recovering America’s Wildlife Act of 2021, introduced in the House by Democratic Rep. Debbie Dingell of Michigan, would boost total funding available to tribes for wildlife work. In the meantime, Higley holds the course: “For us, as long as we have the funding to do anything, we should keep doing anything we have been doing.”
He is, in some ways, haunted by a previous gap: In the 1990s, researchers found an abundance of fishers, then paused while funding lapsed, and resumed in 2005. Soon, his group recognized the population had crashed. “It was just mind-blowing to me—orders of magnitude fewer fishers out there, and we’ll never know why for sure,” he said.
Fishers, clearly, are sensitive animals that need to be monitored, Higley said, but even now, budget constraints make it difficult to tell whether the current population is stable. “When you kind of pull back that bare minimum of work, it’s hard to really get a good feel for it,” he said. Colegrove said he thinks the population has declined since he started helping to trap and monitor them more than a decade ago. “Back in the day, we’d catch one to three a day,” he said. “Now, we’ll go weeks without catching a fisher.”
Colegrove hopes to eventually write more papers using data collected at Hoopa, and he has an eye on growing the wildlife division’s work. He’d like to make it a resource for tribal members who want to hunt these species or know better what’s going on with everything from pileated woodpeckers, also used in regalia, to deer, which figure in every ceremony and provide food and blankets.
“Our culture has everything to do with our resources, our animals, our land, our water—everything that we’ve learned as people came from the landscape, came from the land,” he said.
At the tailgate, Colegrove watched the fisher’s jaw tighten and eyelids twitch as the sedatives wore off. Horan moved it into a clean trap and then drove the mud-slick roads to where it had been caught. On a fallen moss-carpeted tree, Horan set down the trap and opened its door. The fisher’s bushy tail curled out first, followed by a wary eye and nose. Next, its whole body emerged in a burst, bounding down the log, then sprinting away through the brush.