ASSESSMENT OF SHORT-TERM EFFECTIVENESS OF ARTIFICIAL RESTING AND DENNING STRUCTURES FOR THE HUMBOLDT MARTEN (MARTES CAURINA HUMBOLDTENSIS) IN HARVESTED FORESTS IN NORTHWESTERN CALIFORNIA By Matthew S. Delheimer A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Natural Resources: Wildlife Committee Membership Dr. Micaela Szykman Gunther, Committee Chair Dr. Matthew Johnson, Committee Member Dr. William Zielinski, Committee Member Keith Slauson, Committee Member Dr. Yvonne Everett, Graduate Coordinator July 2015 ABSTRACT ASSESSMENT OF SHORT-TERM EFFECTIVENESS OF ARTIFICIAL RESTING AND DENNING STRUCTURES FOR THE HUMBOLDT MARTEN (MARTES CAURINA HUMBOLDTENSIS) IN HARVESTED FORESTS IN NORTHWESTERN CALIFORNIA Matthew S. Delheimer The Humboldt marten (Martes caurina humboldtensis) is a habitat specialist that requires large, old woody structures such as live trees, snags, and logs to provide suitable resting and denning locations. Many timber harvesting practices remove these woody structures and harvested forests typically have a poor availability of suitable resting and denning locations for martens. Artificial structures (“marten boxes”) may increase the availability of resting and denning locations for martens in harvested forests by acting as surrogates for natural woody structures. Increasing the availability of resting and denning locations may improve suitability of harvested forest stands and thereby accelerate marten recolonization of harvested forests. In 2013, I deployed 55 marten boxes among three study sites in northwestern California. I monitored animal visitation and animal use with remote cameras at 43 boxes for approximately 12 months and detected 10 mammalian species. Douglas squirrel (Tamiasciurus douglasii) was the most common small mammal species and fisher (Pekania pennanti) was the most common carnivore species visiting boxes. Animal use of boxes (i.e., entering the box) was rare but was documented for four species, including marten. Track plate surveys conducted ii prior to box deployment indicated that the Goose Creek and Mill Creek study sites were not marten-occupied; however, naïve occupancy estimates at the two sites were significantly different for three out of five other carnivore species detected. Habitat transects revealed that Pecwan Creek, the marten-occupied site, had a significantly higher density of potential resting structures for martens than the Goose Creek or Mill Creek sites. Differences between study sites in terms of box visitation, species occupancy, and potential resting structure availability may be the result of different animal species assemblages, dominant forest types, forest management histories, or other processes. My data demonstrate visitation and use of boxes by martens; however, longer-term monitoring of boxes will likely be necessary to better understand their effectiveness as a conservation tool for the Humboldt marten. iii ACKNOWLEDGEMENTS This project was made possible through the collaboration, guidance, and support of numerous agencies, organizations, and individuals. First off, I would like to thank my committee members: Dr. Micaela Szykman Gunther, for taking me on as a student and guiding me through process; Dr. William Zielinski, for his enthusiasm, accessibility, and thoughtful input; Dr. Matthew Johnson, for his insightful ideas; and Keith Slauson, for developing the marten box project, allowing me to execute it, and continuing to provide feedback and support. In addition to my committee members, there is a long list of folks who deserve recognition for their efforts. Thanks to Travis Langer at the USDA Forest Service/Redwood Sciences Lab (RSL) for being the marten box construction foreman, and for truly getting the project off the ground. Ric Schlexer at RSL and Brenda Devlin at Six Rivers National Forest provided logistical support. Amber Transou and Jay Harris at California State Parks provided field equipment and knowledge of the Mill Creek watershed. Anthony Desch at Humboldt State University allowed me to raid the Wildlife stockroom of some of its best cameras and a lot of batteries. Keith Hamm and Desiree Early at Green Diamond Resource Company provided logistical support at the end of the project. Dan Barton and Tim Bean at Humboldt State University offered valuable input on the occupancy component of the analysis. The assistance of interns, volunteers, and undergraduate students was invaluable to the success of this project. Special thanks to Nalani Ludington, for putting up with me iv for my entire first summer of field work. Matthew Fountain and Gary Sousa provided integral assistance during the occupancy surveys. Rachel Guinea, Riley Gorman, Rachel Nypaver, and Abby Rutrough aided in the most difficult part, getting the marten boxes off the ground. Many thanks to the Save-The-Redwoods League for initial financial support. The USDA Forest Service/Redwood Sciences Lab contributed additional financial support, as well as logistical support, remote cameras, field equipment, field vehicles, and much else. California State Parks provided the raw redwood material for the marten boxes and a number of remote cameras. California State Parks and Redwood National and State Parks, Green Diamond Resource Company, and the Yurok Tribe graciously allowed me to travel across and work on their lands. And last but not least, thanks to all of the individuals, organizations, and agencies involved in the Humboldt Marten Conservation Group for their continuing dedication to protecting and restoring the Humboldt marten throughout its historical range. v TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii LIST OF APPENDICES .................................................................................................... ix INTRODUCTION .............................................................................................................. 1 STUDY AREA ................................................................................................................... 9 MATERIALS AND METHODS ...................................................................................... 12 Marten Box Deployment .............................................................................................. 12 Track Plate Surveys ...................................................................................................... 14 Marten Box Monitoring ................................................................................................ 16 Habitat Transects .......................................................................................................... 18 RESULTS ......................................................................................................................... 22 Track Plate Surveys ...................................................................................................... 22 Marten Box Monitoring ................................................................................................ 24 Habitat Transects .......................................................................................................... 28 DISCUSSION ................................................................................................................... 32 MANAGEMENT IMPLICATIONS AND CONCLUSIONS .......................................... 39 LITERATURE CITED ..................................................................................................... 43 APPENDICES .................................................................................................................. 56 vi LIST OF TABLES Table 1. Naïve occupancy of five carnivore species at the quadrant (n=40 per site) scale at the Goose Creek and Mill Creek study sites in northwestern California, July to September 2013. ............................................................................................................... 23 Table 2. Density (mean number of structures per hectare) of resting structures for the Humboldt marten at the Goose Creek, Mill Creek, and Pecwan Creek study sites in northwestern California, July to October 2014. Includes standing structure density, ground-based structure density, and total structure density (combined standing and ground-based structure densities). Standard error (SE) estimate in parentheses. ............ 29 Table 3. Density (mean number of structures per hectare) of standing resting structures for the Humboldt marten at the Goose Creek, Mill Creek, and Pecwan Creek study sites in northwestern California, July to October 2014. Includes live conifer density, live hardwood density, live tree density (combined live conifer and live hardwood densities), and snag density. Standard error (SE) estimate in parentheses. ...................................... 31 vii LIST OF FIGURES Figure 1. Study area including land ownership boundaries and marten box locations at three study sites in northwestern California. ....................................................................