Paper published on Washington fisher reintroduction

We contributed to a new study in the Journal of Wildlife Management assessing the habitat preferences of fishers recently reintroduced to Washington’s Cascade Mountains.

BY DAVE WERNTZ, SCIENCE AND CONSERVATION DIRECTOR

As the lead for Conservation Northwest’s collaborative program reintroducing fishers to Washington, I was proud to contribute to a new study and scientific paper published last month. Habitat Selection and Spatiotemporal Interactions of a Reintroduced Mesocarnivore examines how reintroduced fishers choose habitat and interact with other wildlife. Also included in the paper are our project partners from the National Park Service and the Washington Department of Fish and Wildlife, as well as excellent researchers from the University of Washington.

While it is well established that fishers use large, old trees and snags in primarily mid-elevation, old-growth forests for denning and rest sites, little is known about how the presence of predators, such as bobcats and coyotes, plays a role in a fisher’s habitat preference.

From December 2015 to September 2017, we monitored fishers and their prey and predators in a 10,000-km² study area, which included the Gifford Pinchot National Forest, Mount Rainier National Park, and other state and private lands in Washington’s South Cascades. During this time, 69 total fishers were released into this landscape. We set up 134 remote camera stations, aerial and ground telemetry surveys, and used remotely-sensed forest structure data to assess how predators, prey and forest structure affected fishers’ habitat selection.

We learned that fishers prefer habitat in old forests, including those near recently disturbed areas, commonly known as “edge habitat”, as well as forests with moderate levels of snowshoe hare activity. Bobcats and coyotes did not directly affect fisher habitat selection, but fishers did tend to avoid areas with high snowshoe hare and bobcat activity. This may indicate a “food-safety tradeoff”—where the potential for competition and predation from bobcats is too risky, so areas with moderate snowshoe hare activity are more preferable for fishers.

Food-safety tradeoffs are a fairly common but always interesting biological phenomena: wild animals accepting lower food availability for a higher chance of avoiding being eaten by larger predators!

Temporally, fishers tended to have a diurnal activity pattern, with the highest activity from morning to mid-day. As we predicted, this was the flipside of activity patterns of coyotes and bobcats, which are predominantly nocturnal and crepuscular (twilight), respectively.

This research helps provide a clearer picture of how fishers are adjusting to life after reintroduction in Washington’s Cascade Mountains. Like many of us, they’re seeking that ideal combination of quality food and safe housing.

Abstract from the Journal of Wildlife Management

Habitat quality and quantity are key factors in evaluating the potential for success of a wildlife translocation. However, because of the difficulty or cost of evaluating these factors, habitat assessments may not include valuable information on important habitat attributes including the abundance and distribution of prey, predators, and competitors.

Fishers (Pekania pennanti) are one of the most commonly reintroduced carnivores in North America, and they are a species of conservation concern in their western range. We examined the relative importance of landscape features and species interactions in determining habitat use of a reintroduced population of fishers in the southern Cascade Mountains, Washington, USA. We used detections of prey and predators at 134 remote camera stations, remotely sensed forest structure data, and telemetry locations of fishers in a resource selection function to assess the relative importance of prey, predators, and forest structure in fisher habitat selection.

Fishers selected habitats based on forest conditions and activity levels of snowshoe hares (Lepus americanus), whereas bobcat (Lynx rufus) and coyote (Canislatrans) activity levels did not directly affect habitat selection. The probability of fisher use increased in older stands, close to recently disturbed stands, and in areas with intermediate levels of hare activity. Bobcat and hare activity levels were positively correlated, and fishers avoided areas with the greatest hare activity, suggesting that fishers may experience a food‐safety tradeoff in the study area. Temporal activity patterns in photo detections indicate that fishers may mediate this danger by avoiding bobcats temporally.

Our findings suggest that fishers in Washington prefer habitat mosaics of old and recently disturbed stands where they have greater access to resting structures and hares. Management that maintains mosaics of young and old forest across large landscapes is likely to support fisher recovery. Future reintroduction efforts would benefit from an assessment of prey and predator abundance in proposed reintroduction areas before project initiation.

KEEP READING THE ARTICLE, OR LEARN MORE ABOUT OUR WORK TO RESTORE FISHERS IN WASHINGTON!