A hundred miles south of Oregon, in one of the last small pockets of its historical West Coast range, an elusive, housecat-sized member of the weasel family is struggling to survive.
The fisher — sometimes known as fisher cat — made headlines this fall when U.S. Fish and Wildlife officials proposed protections for the West Coast population of the species, citing threats including the widespread use of rat bait at illegal marijuana farms: The poison doesn’t cause instant death but slowly kills its way up the food chain — and it has proven devastating to the carnivorous fisher.
With an already imperiled population at stake, researchers in California’s Humboldt County — the epicenter of the poisoning problem — are seeking to minimize another potential threat to fishers by determining how the species’ denning behavior might be affected by a local timber industry that reaches its peak of activity just when fishers are raising their young.
Conventional study methods have proven prohibitively expensive and invasive. But with a $3,984 Future for Wildlife grant from the Oregon Zoo, a team at Humboldt State University has devised a technique that might help protect fishers while making inexpensive, non-invasive monitoring technology available to wildlife researchers everywhere. The innovation was guided in part by the negative impacts that the fisher researchers themselves might have on their subjects.
“Fishers den in trees, and researchers walking near their dens while the mother is present can have negative consequences for the fisher and her kits,” said Caylen Cummins, the Humboldt State graduate student leading the study. “It might prompt the mother to move her kits to new dens more frequently than she otherwise would, putting herself and her kits at great risk as she carries them one by one to a new tree.”
To study the fishers’ behavior without disturbing their maternity wards, Cummins devised her own homemade data-loggers — at a tenth of the price of commercial units — to remotely track the animals’ movements.
Last month, Cummins and her team began live-trapping fishers, taking blood samples to inform ongoing poison-monitoring studies, and returning the fishers to the wild. When they trap a female of reproductive age, they also fit her with a tracking collar.
If they find she’s been holed up in the same tree for at least three days, they know she’s started denning, and at that point, the team places Cummins’ data-logging device — essentially a machine that listens to and interprets a radio pulse through a headphone jack, eliminating the need for human ears.
The machine knows when the fisher comes and goes, and can even help estimate how many kits she has if she moves them. The fisher’s movements are then compared against variables such as temperature changes or sounds from human activity.
Cummins hopes her research will help identify what particular variables — for example, road construction — have the highest impact on fisher den-attendance behavior. Forest managers can then use that data to potentially defer human activities to more fisher-friendly months of the year.
“Leave it to a graduate student with limited resources to come up with a novel and frugal idea,” said Micaela Szykman Gunther, the study’s principal investigator and Cummins’ graduate advisor. “Thanks to Caylen and her colleagues’ ingenuity, we’re able to conduct a $45,000 study for less than $4,000, and the Future for Wildlife grant is making it possible.”