DIETARY OVERLAP OF FISHERS AND PACIFIC MARTENS IN RESPONSE TO TREE MORTALITY IN SIERRA NEVADA FORESTS.
G. Brad Smith; Department of Wildlife Ecology, University of Wisconsin; 1630 Linden Dr., Madison, WI, 53706; gbsmith3@wisc.edu; Jonathan N. Pauli, Jody M. Tucker
Shifts in primary producers within forest communities can have cascading effects on higher trophic levels, including carnivores. In the Sierra Nevada mountains, a high severity, multi-year drought (2012-2015), coupled with bark-beetle outbreaks, has resulted in widespread tree mortality that has dramatically altered the composition of forests. Fishers (Pekania pennanti) and Pacific martens (Martes caurina) are two carnivores of conservation concern associated with late-successional mixed forests throughout this region. It is currently unknown how these recent changes in forest conditions affect prey sources for fisher and marten. We predicted that tree mortality would simplify the available forage, and drive increased competition between these two similar species. To quantify these impacts, we identified hair samples (n = 128) collected from fishers and martens from 2006-2018 for analysis of stable isotope signatures. Preliminary results show variation in dietary inputs amongst locations, and limited dietary overlap between fishers and martens, in general. We are currently exploring temporal trends in dietary composition, niche dynamics, and competitive overlap for martens and fishers for the pre-drought (2006-2011), drought (2012-2015), and tree mortality (2016-present) periods.
Ecology and Conservation of Martens and Fishers   Student Paper