Reintroducing fishers to forest ecosystems in Washington State, USA

Summary

Fishers, mid-sized forest carnivores, were wiped out across the southern part of their North American range, including Washington State, by unregulated trapping, habitat loss and predator-control campaigns through the mid-1900s. Following a 2004 feasibility study that identified suitable old-growth forest habitat in three recovery areas and a genetically well-matched source population in central British Columbia, Washington Fish and Wildlife and partner agencies released 90 fishers into Olympic National Park between 2008 and 2010, tracked by VHF radio collar, and have since released a further 69 into the southern Cascades starting in December 2015, with a northern Cascades release beginning in 2017. On the Olympic Peninsula, released fishers often travelled far before settling, averaging 44.5 km for males and 30.1 km for females, with markedly more females (67 percent) than males (38 percent) establishing home ranges; seven confirmed litters were recorded among founder females within a few years. A 2013 to 2016 occupancy survey using DNA analysis found fishers now widely distributed across the peninsula, including second- and third-generation animals, evidence of substantial natural reproduction. Aerial radio-tracking across rugged, roadless terrain proved the main monitoring challenge, and lessons from the Olympic effort, including releasing more animals before pregnancy season and favouring fewer, closer-together release sites, are now shaping the ongoing Cascades reintroductions. The project rates itself as showing strong positive signs, though formal evaluation is still underway.