Southern Sierra Nevada Fisher Conservation Assessment Prepared By Wayne Spencer Sarah Sawyer Heather Romsos William Zielinski Rick Sweitzer Craig Thompson Kathryn Purcell Deana Clifford Lindsay Cline Hugh Safford Susan Britting Jody Tucker Prepared For The Fisher Interagency Leadership Team: Sierra Nevada Conservancy USDA Forest Service National Park Service US Fish and Wildlife Service California Department of Fish and Wildlife January 2015 Produced by the Conservation Biology Institute. CBI is a 501(c)3 tax-exempt organization that works collaboratively to conserve biological diversity in its natural state through applied research, education, planning, and community service. Recommended Citation: Spencer, W.D., S.C. Sawyer, H.L. Romsos, W.J. Zielinski, R.A. Sweitzer, C.M. Thompson, K.L. Purcell, D.L. Clifford, L. Cline, H.D. Safford, S.A. Britting, and J.M. Tucker. 2015. Southern Sierra Nevada fisher conservation assessment. Unpublished report produced by Conservation Biology Institute. Fisher Interagency Leadership Team: Barnie Gyant, USDA Forest Service Region 5 Cay Goude, US Fish and Wildlife Service David Graber, PhD National Park Service (retired) Kent Smith (retired) and Eric Loft, California Department of Fish and Wildlife Jim Branham, Sierra Nevada Conservancy Core Project Support Team: Diana Craig, USDA Forest Service Sarah Sawyer, PhD, USDA Forest Service Wayne Spencer, PhD, Conservation Biology Institute Mandy Vance, Sierra Nevada Conservancy Fisher Technical Team: Wayne Spencer, PhD (Chair), Conservation Biology Institute Sarah Sawyer, PhD, USDA Forest Service Region 5 Susan Britting, PhD, Sierra Forest Legacy Deana Clifford, DVM, MPVM, PhD, California Department of Fish and Wildlife Lindsay Cline, MS, National Park Service Roger Powell, PhD, North Carolina State University (Emeritus) Kathryn Purcell, PhD, Pacific Southwest Research Station Hugh Safford, PhD, USDA Forest Service Region 5 and University of California, Davis Rick Sweitzer, PhD, Great Basin Institute Craig Thompson, PhD, Pacific Southwest Research Station Jody Tucker, PhD, USDA Forest Service Region 5 William Zielinski, PhD, Pacific Southwest Research Station ii Contents Tables .......................................................................................................................... iv Figures ......................................................................................................................... v Abbreviations, Acronyms, and Definitions ....................................................................... vii Preface ...................................................................................................................... viii Acknowledgments ......................................................................................................... x 1 Introduction ........................................................................................................... 1 1.1 Context .............................................................................................................................. 1 1.2 Objectives and Scope ......................................................................................................... 4 2 Population Distribution and Trends .......................................................................... 6 2.1 Range Size and Trends ........................................................................................................ 6 2.2 Elevation Distribution ......................................................................................................... 7 2.3 Population Size and Trends ................................................................................................ 7 2.4 Genetic Diversity and Population Subdivision ..................................................................... 9 3 Fisher Biology and Ecology .....................................................................................11 3.1 Life History ....................................................................................................................... 11 3.1.1 Reproduction ........................................................................................................... 11 3.1.2 Survivorship ............................................................................................................. 12 3.1.3 Mortality causes ....................................................................................................... 12 3.2 Ecology ............................................................................................................................ 17 3.2.1 Space use patterns ................................................................................................... 17 3.2.2 Activity patterns ....................................................................................................... 21 3.2.3 Diet .......................................................................................................................... 22 3.2.4 Interspecific competition .......................................................................................... 24 4 Habitat Associations...............................................................................................26 4.1 Landscape Scale ............................................................................................................... 26 4.2 Home Range Scale ............................................................................................................ 27 4.3 Sub-home Range Scale ..................................................................................................... 29 4.3.1 Foraging ................................................................................................................... 29 4.3.2 Resting habitat and structures .................................................................................. 30 4.3.3 Denning habitat and structures ................................................................................ 33 5 Habitat Core and Linkage Areas ..............................................................................41 5.1 Fisher Core Areas ............................................................................................................. 41 5.1.1 Core Area 1 .............................................................................................................. 44 5.1.2 Core Area 2 .............................................................................................................. 44 5.1.3 Core Area 3 .............................................................................................................. 46 5.1.4 Core Area 4 .............................................................................................................. 47 5.1.5 Core Area 5 .............................................................................................................. 49 5.1.6 Core Area 6 .............................................................................................................. 50 5.1.7 Core Area 7 .............................................................................................................. 52 5.2 Linkage Areas ................................................................................................................... 52 5.2.1 Linkage A .................................................................................................................. 53 5.2.2 Linkage B .................................................................................................................. 53 5.2.3 Linkage C .................................................................................................................. 53 5.2.4 Linkage D .................................................................................................................. 53 5.2.5 Linkage E .................................................................................................................. 55 5.2.6 Linkage F .................................................................................................................. 55 iii 6 Threats Assessment ...............................................................................................57 6.1 Habitat Loss and Fragmentation ....................................................................................... 57 6.1.1 Large and severe wildfires ........................................................................................ 57 6.1.2 Lack of fire as a natural disturbance process ............................................................. 59 6.1.3 Post-fire habitat management .................................................................................. 60 6.1.4 Vegetation management .......................................................................................... 63 6.2 Rodenticides and Other Poisons ....................................................................................... 65 6.3 Predation ......................................................................................................................... 66 6.4 Disease and Infections...................................................................................................... 66 6.5 Roads and Other Human Structures ................................................................................. 68 6.6 Climate Change Effects ..................................................................................................... 69 6.6.1 Physiological ............................................................................................................