An Expanding Meso-Carnivore: Fisher (Pekania pennanti) Occupancy and Coexistence with Native Mustelids in Southeast Alaska

• Main Author: Kupferman, Caitlin
• Other Authors: Gilbert, Sophie
• Format: Text
• Language: English
• Published: 2019
• Subjects: alaska; competition; ermine; fisher; marten; occupancy; Wildlife conservation; American marten; Martes americana; Alaska
• Online Access: http://digital.lib.uidaho.edu/cdm/ref/collection/etd/id/1335

Around the world, species’ distributions are shifting in response to climate change, with many species exhibiting range expansion toward the poles. These range expansions often create new species interactions that are not well understood. The fisher (Pekania pennanti) is a mammalian carnivore that has recently expanded its range into the coastal temperate rainforest of Southeast Alaska (SEAK). Little is known about its occupancy and effects on native species in SEAK. The goal of this project was to examine fisher occupancy, density, and co-occurrence with American marten (Martes americana) and ermine (Mustela erminea) in SEAK. Twenty-five paired camera and hair snag stations (50 unique sites) were deployed north of Juneau, Alaska from January−April 2018, resulting in detection of 15 species and collection of 204 hair samples. Polymerase chain reactions conducted on DNA extracted from hair samples showed that 16 of those hair samples were from fisher. From the fisher DNA samples, only one individual fisher was identifiable (a female), making a fisher density analysis unfeasible. However, camera trap data allowed us to conduct single species occupancy analyses at both local and broad scales, which showed that fisher detection was negatively impacted by snow density, but positively affected by whether a fisher had been detected at the previous occasion (average site scale p = 0.24 (95% CI = 0.12, 0.40); average grid scale p = 0.15 (95% CI = 0.07, 0.30)). Fisher occupancy was positively impacted by snow density at the local scale and positively associated with vegetation height at a broader scale (average site scale psi = 0.30 (95% CI = 0.08, 0.72); average grid scale psi = 0.40 (95% CI = 0.003, 0.83)). Although high snow density has the potential to decrease the impact of a fisher’s high foot-load by making it easier to travel on top of the snow, the effect may not be powerful enough to overcome the high energetic costs associated with movement in deep snow and therefore not positively contribute to detectability ...