Drought-induced tree mortality affects the space-use and individual plasticity of an endangered forest carnivore

Marie Martin , Rebecca Green, Eric McGregor, Sean Matthews, Kathryn Purcell, Craig Thompson

Rapid changes in landscape structure can disrupt the ecology and life history of species of conservation concern. Shifting climate, land-use, and disturbance regimes are generating novel landscape patterns, and it is unclear how these novel conditions may affect imperiled species. In the Sierra Nevada of California, USA, extensive drought-induced tree mortality has rapidly altered forest structure and local microclimates, with potential implications for forest-dependent species. We evaluated the effects of shifting land cover, forest structure, and abiotic conditions on the space-use of federally-endangered fishers (Pekania pennanti) in the southern Sierra Nevada during three distinct periods – pre-drought, drought, and post-drought tree mortality. Using 12 years of space-use data from 102 VHF- and GPS-collared fishers, we found that fishers selected for cooler, more forested, and riparian portions of the landscape across time periods. However, during drought and tree mortality, the magnitude of selection shifted strongly, with fishers selecting for remnant live and dead forest, riparian areas, and cooler areas and strongly avoiding open areas. As tree mortality occurred individual variation strongly increased, indicating the potential for adaptive behavior. Our results highlight the importance of individual plasticity and landscape composition in imperiled species persistence and demonstrate the risks of forest loss and change due to shifting climate and disturbance regimes.