DROUGHT AND COYOTES MEDIATE THE RELATIONSHIP BETWEEN MESOPREDATORS AND HUMAN DISTURBANCE IN CALIFORNIA By Molly Kelley Parren 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. Barbara Clucas, Committee Chair Dr. Daniel Barton, Committee Member Dr. William T. Bean, Committee Member Dr. Erin Kelly, Graduate Coordinator December 2019 ABSTRACT DROUGHT AND COYOTES MEDIATE THE RELATIONSHIP BETWEEN MESOPREDATORS AND HUMAN DISTURBANCE IN CALIFORNIA Molly Kelley Parren Mesopredators in California are facing two major changes to their ecosystem: drought and the expansion of human disturbance. As a result, mesopredators are likely shifting their habitat use as well as their interspecies interactions to balance resource needs and risk-taking on the landscape. In response to severe drought, the California Department of Fish and Wildlife deployed 585 camera traps throughout the Mojave Desert and Central Valley documenting mammalian mesopredator presence in a drought year (2016) and a post-drought year (2017). The objectives of this study were to examine spatial patterns of mesopredator occurrence and co-occurrence with a dominant predator, the coyote (Canis latrans), at a large spatial scale across varying levels of human disturbance and to investigate how drought may mediate these relationships. Single- season, single-species occupancy models were used to elucidate the relationship between human disturbance, drought, and mesopredator habitat use in both ecoregions. Conditional two-species occupancy models were then fit to establish the effect coyotes may have had on subordinate mesopredators and their relationships with human disturbance during and after the drought. I found that human disturbance differentially affected both the occupancy and detection of mesopredator species and that these ii relationships were sometimes mediated by drought and the presence of coyotes. Except for the domestic cat (Felis catus), all mesopredators showed some kind of response to drought. Detection of mesopredators in the Central Valley was typically higher in 2016, especially in low disturbance sites, indicating that species became more active during the drought to meet resource needs. However, detection and occupancy of mesopredators in the Mojave Desert tended to increase after the drought, suggesting that species were responding to an increase in resources, possibly the density of prey. Coyotes in the Mojave Desert became more detectable in high human disturbance in 2016 and less detectable in 2017, signifying that they were increasing activity in human disturbance during the drought, possibly to obtain anthropogenic resources. Additionally, subordinate species, particularly in the Central Valley, appeared to take greater risks during the drought with increased use of water sources, despite the presence of coyotes. These findings suggest that drought not only affects individual species and their relationships to human disturbance, but that it can also impact their interspecies interactions and use of different landscape features. iii ACKNOWLEDGEMENTS The data and funding for this project were provided by the California Department of Fish and Wildlife. I thank them for the opportunity to work first as a field technician on this project and then as a graduate student; the experience has been invaluable. Special thanks to Dr. Brett Furnas, Misty Nelson, and Scott Newton who made this large scale monitoring project a reality. Thanks also to the many technicians who made data collection possible with a special thank you to Bri Milano and Griffin Capehart who made two seasons at Camp “Candy” both survivable and fun. Additional thanks to Dr. Lindsey Rich for her contribution to the project and for her patience and kindness helping me along the way. Thanks also to Dr. Ange Baker for her help and support in the analysis portion of this project. Additional funding was provided by the Rotary Club of Eureka, I thank them for their support and belief in me and my project. I am endlessly grateful to Dr. Barbara Clucas, my advisor, who took a chance on me as her first graduate student. She has been supportive, generous, and kind for the past three years and I couldn’t be more thankful. Thanks also to my committee members Dr. Tim Bean and Dr. Dan Barton for their help and support along the way; this project would not have been possible without them. My time at Humboldt State University has pushed me to become both a better scientist and person, and for that I am grateful. Graduate school would have been much more of a struggle if it had not been for the friendship and comradery of my fellow students. A special thank you to the Wildlife Graduate Student Society and my labmates: Trinity Smith, Chad Moura, Leigh Douglas, iv and Travis Farwell. Additional thanks to all of my friends, especially the “Tailgate Committee”, for the laughter and much-needed time in big trees and on the beach. And a shout-out to Maddie Halloran: I could not have wished for a better friend in graduate school- thanks for making the past years a lot less lonely and a lot more fun. Finally, a big thank you to my family: your endless love and support has made every accomplishment in my life possible. To Nora: you are one of the smartest and most generous people I know, thank you for letting me vent and telling me that you are proud of me no matter what. I love you and am lucky to have you as a sister. To my mother, Lauren: your patience and unending support are what keep me afloat when my emotions and self-doubt start to take over. Thank you for teaching me, believing in me, buying me my first house plants, and then listening to me talk about my houseplants for the next 2+ years. I love you and hope to one day be as kind and empathetic as you are. And finally, to my father, Steve (aka: Mr. Wildlife Guy): your commitment to conservation and doing the right thing, even if it isn’t the easiest thing, is inspiring. Admittedly, there were times growing up where having a wildlife biologist for a dad wasn’t my favorite (cue cassette 976 of bird calls) but I am forever grateful that you are. Thank you for introducing me to the world of science, for letting me “help” even when I’m sure I wasn’t, and for instilling a love of the natural world in me. Without the early days of nature shows on PBS, searching for salamanders in the stream, and yes, even “ignoring you” while you tried to teach me my birds, I would not be here today. Thank you, I love you. v TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iii TABLE OF CONTENTS .................................................................................................... v LIST OF TABLES ............................................................................................................. ix LIST OF FIGURES ............................................................................................................ x LIST OF APPENDICES ................................................................................................... xv INTRODUCTION .............................................................................................................. 1 MATERIALS AND METHODS ...................................................................................... 11 Site Locations ............................................................................................................... 11 Mojave Desert ........................................................................................................... 11 Central Valley ........................................................................................................... 11 Site Selection and Study Design ................................................................................... 12 Camera Trap Data Collection ....................................................................................... 15 Data Analysis and Occupancy Modeling ...................................................................... 18 Camera trap photo processing ................................................................................... 18 Single season occupancy modeling .......................................................................... 18 Conditional two-species occupancy modeling .......................................................... 30 RESULTS ......................................................................................................................... 35 Single-Season Single-Species Occupancy Models ....................................................... 36 Mojave Desert ........................................................................................................... 36 Central Valley ........................................................................................................... 52 vi Conditional Single-Season Two-Species Occupancy Models ...................................... 63 Mojave Desert ........................................................................................................... 63 Central Valley ........................................................................................................... 71 DISCUSSION ..................................................................................................................