Occupancy Patterns in a Reintroduced Fisher Population during Reestablishment

• Published in: The Journal of wildlife management 2020-02, Vol.84 (2), p.344-358
• Main Authors: HAPPE, PATRICIA J., JENKINS, KURT J., MCCAFFERY, REBECCA M., LEWIS, JEFFREY C., PILGRIM, KRISTINE L., SCHWARTZ, MICHAEL K.
• Format: Article
• Language: English
• Subjects: Cameras; Coverage; Deoxyribonucleic acid; DNA; Fish populations; fisher; Forest ecosystems; Forest management; Forests; Habitat Relations; Habitats; noninvasive genetic sampling; Occupancy; Olympic Peninsula; Pekania pennanti; Population; Population distribution; Population studies; Predictions; Prey; Reintroduction; Resource availability; Restoration; Terrestrial ecosystems; Translocation; Wilderness; Wilderness areas; Wildlife; Wildlife habitats; Wildlife management
• ISSN: 0022-541X; 1937-2817
• DOI: 10.1002/jwmg.21788

Monitoring population performance in the years following species reintroductions is key to assessing population restoration success and evaluating assumptions made in planning species restoration programs. From 2008–2010 we translocated 90 fishers (Pekania pennanti) from British Columbia, Canada, to Washington’s Olympic Peninsula, USA, providing the opportunity to evaluate modeling assumptions used to identify the most suitable reintroduction areas in Washington and enhance understanding of fisher habitat associations in the late-successional forest ecosystems in the coastal Pacific Northwest. From 2013–2016, we deployed 788 motion-sensing cameras and hair (DNA)-snaring devices distributed among 263 24-km² primary sampling units across the Olympic Peninsula. Our objectives were to determine whether occupancy patterns of the reestablishing population supported assumptions of the initial habitat assessment models, whether the population had expanded or shifted in distribution since the initial reintroductions, compare physical habitat attributes among land-management designations, and determine whether the founding fishers had successfully reproduced. We predicted that site occupancy by fishers would be associated with landscapes characterized by high proportional coverage of dense forest canopies and medium-sized and large trees, a diversity of stand structural classes, and area near the administrative boundary separating wilderness from more intensively managed forest lands. We detected fishers across designated wilderness, federal lands outside of wilderness, and other land designations in proportion to land availability on the Peninsula. We found negligible support for predictions that occupancy by fishers was associated with percent forest cover, tree-size class, or structural class diversity. Rather, occupancy was strongly associated with lands near the wilderness boundary on both sides. We speculate that the boundary between wilderness and more intensively managed forest lands provided fishers with the most suitable prey in proximity to contiguous expanses of low- to midelevation late-successional forests that provided optimal resting, denning, and security values. Occupancy patterns shifted toward the west and south along a precipitation gradient during the study, indicating that population distribution had not yet stabilized 5–8 years following translocation. Genetic results indicated that ≥2 generations of fishers have been produced on the Peninsul