Mesocarnivore Responses to Changes in Habitat and Resource Availability in California
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Mesocarnivore responses to changes in habitat and resource availability in California by Allison Lynn Bidlack B.S. (University of Michigan) 1992 M.S. (University of Alaska Fairbanks) 2000 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Environmental Science, Policy and Management in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Wayne M. Getz, Co-Chair Professor Adina M. Merenlender, Co-Chair Professor Wayne P. Sousa Fall 2007 Mesocarnivore responses to changes in habitat and resource availability in California Copyright 2007 by Allison Lynn Bidlack ABSTRACT Mesocarnivore responses to changes in habitat and resource availability in California by Allison Lynn Bidlack Doctor of Philosophy in Environmental Science, Policy and Management University of California, Berkeley Professor Wayne M. Getz, Co-Chair Professor Adina M. Merenlender, Co-Chair Effective conservation of mammalian carnivores requires knowledge of their ecologies in both natural and altered habitats, especially in regions experiencing substantial human population growth. The research presented in this dissertation addresses the relationship between carnivores and habitat change, and investigates the magnitude of temporal and spatial population fluctuations and the processes behind them in both natural and urbanizing systems. To examine these fluctuations in carnivore populations, and the contribution of long-term studies to our understanding of these changes over time, I compared San Joaquin kit fox population numbers with rainfall and prey data collected over 35 years on the Carrizo Plain, California. Seasonal rainfall levels were a poor predictor of interannual kit fox numbers, although I did find a correlation between fox numbers and jackrabbit numbers over time. A spatial congruence between giant kangaroo rat distribution and kit fox distribution was also evident, and both species appeared to be expanding their ranges northward within the portion of the park that had previously been cultivated. Urbanization can also lead to distributional changes and increases in invasive species, threatening native biodiversity. Given this risk, I focused on the relationship between invasive red fox and habitat correlates in the San Francisco Bay area. I found that red foxes were widespread but not locally abundant, and were strongly correlated with urban development and high road densities. No correlation between red fox distribution and other native canids was apparent. Other common mesocarnivores are also responding to urbanization in the San Francisco Bay Area. Coyotes, bobcats and gray foxes were detected at different densities along an urban-to-rural gradient. Both total carnivore abundance and number of species detected were highly negatively correlated with levels of urban development and road density, and coyotes and bobcats tended to avoid urban areas. Coyotes were detected more often in open habitats such as grasslands, while gray foxes strongly preferred hardwood forest. The extent of habitat at different landscape scales was also important, with coyotes reacting at the largest scale, and gray foxes at the smallest. TABLE OF CONTENTS List of figures…………………………………………………………………… ii List of tables……………………………………………………………….…… iv Acknowledgments……………………………………………………………… v CHAPTER 1 Introduction……………………………...…….......………. 1 CHAPTER 2 San Joaquin kit fox (Vulpes macrotis mutica) population dynamics on the Carrizo Plain, California, 1970-2005….. 18 CHAPTER 3 Distribution and habitat use of red fox (Vulpes vulpes) in the San Francisco Bay Area ………..…………………………. 60 CHAPTER 4 Effects of urbanization on mesocarnivores in the San Francisco Bay Area ……………….…………….................. 100 CHAPTER 5 Conclusions and directions for future research….....…..... 143 APPENDIX A Distribution of non-native red foxes in East Bay oak woodlands ……………………………………...................... 153 APPENDIX B Dog training and detection tests ………………….………. 169 APPENDIX C Characterization of a western North American carnivore community using PCR-RFLP of cytochrome b obtained from fecal samples ………………………………………… 180 i LIST OF FIGURES Chapter 2 Figure 1 Map of the Carrizo Plain National Monument and survey transects………………………………………………………… 47 Figure 2 Effective precipitation (November-April) at New Cuyama Fire Station from 1973-2005…..……………………………………. 48 Figure 3 Kit fox, rodent, and jackrabbit counts from the Elkhorn Plain surveys 1970-2005………………………………………………………. 49 Figure 4 Correlation of fox counts, growth rates, and survival against lagged effective rainfall………………………………………………… 50 Figure 5 Elkhorn kit fox sightings 1970-2005 (a); Soda Lake kit fox sightings 1989-2005 (b)…………………………………………………... 51 Figure 6 Elkhorn kit fox sightings (a); Soda Lake kit fox sightings (b); separated into Fall/Winter and Spring/Summer………………... 52 Figure 7 Results of logistic regression of kit fox sightings along Elkhorn and Soda Lake transects from 1989-2005………………………….. 53 Figure 8 Kit fox detections along survey routes in 2001 and 2006, superimposed on giant kangaroo rat distribution……………………………… 54 Chapter 3 Figure 1 Map of San Francisco Bay study area………………………… 87 Figure 2 Red fox survey/sightings locations……………………………. 88 Figure 3 Map of red fox detections during scat surveys by Reed and Bidlack………………………………………………………… 89 Figure 4 Map of all red fox detections………………………………….. 90 Chapter 4 Figure 1 Map of carnivore survey sites in six counties within the San Francisco Bay Area………………………………………………………. 124 Appendix A Figure 1 Location map of survey transects in the East Bay……………. 168 ii Appendix B Figure 1 Percentage of scats placed at different widths from the center line found by detection dog on road and pasture transects………………… 178 Figure 2 Scat detection success regressed against temperature………….. 179 Appendix C Figure 1 Schematic of cutting patterns created by restriction enzymes HpaII, DdeI and HpyCh4V………………………………………………….. 189 Figure 2 Agarose gel restriction enzyme banding patterns for seven species…………………………………………………………. 190 iii LIST OF TABLES Chapter 2 Table 1 Missing survey dates for Elkhorn and Soda Lake routes……….. 55 Table 2 Kit fox and jackrabbit population variables regressed against predictors………………………………………………………… 56 Table 3 P-values of t-tests of mean differences between above- and below- average rainfall years……………………………………………. 57 Table 4 Results of X2 contingency analyses of seasonal differences in sightings along the Soda Lake and Elkhorn survey routes………………… 58 Chapter 3 Table 1 Results of scat survey transects…………………………………. 91 Table 2 List of predictor variables used in logistic regressions………….. 96 Table 3 Summary of transects and scat detections by county…………… 97 Table 4 Results of univariate logistic regression analysis……………….. 98 Table 5 The best multiple logistic regression model for red fox presence. 99 Chapter 4 Table 1 Results of scat survey transects…………………………………. 125 Table 2 List of predictor variables used in logistic and linear regressions 129 Table 3 Results of univariate logistic regressions for coyotes (a); gray foxes (b); bobcats (c)………………………………………………………. 130 Table 4 Results of multiple logistic regressions for coyote (a); gray foxes (b); bobcats (c)………………………………………………………. 133 Table 5 Results of univariate linear regressions for coyote (a); gray foxes (b); bobcats (c)………………………………………………………. 136 Table 6 Results of multiple linear regressions for coyotes and bobcats..... 139 Table 7 Results of univariate linear regressions for scats (a); species (b).. 140 Table 8 Results of multiple linear regressions for all species combined…. 142 iv ACKNOWLEDGMENTS As anyone who has completed a thesis or dissertation knows, it is only through the support of faculty advisors, colleagues, classmates, friends, family members and other important folks that one gets through the process. I would first and foremost like to thank my committee members, Wayne Getz, Adina Merenlender and Wayne Sousa, for all of their support, advice and encouragement. I benefited greatly from their experience and clear thinking. I would also like to thank all the land management agencies and land trusts that gave me access to their properties for this research: California Parks and Recreation; East Bay Regional Park District; Marin County Open Space District; Muir Heritage Land Trust; Napa County Land Trust, including the Wantrup Wildlife Sanctuary; Pepperwood Reserve (California Academy of Sciences); Sonoma County Agricultural Preservation and Open Space District, particularly the Audubon California Mayacamas Mountains Sanctuary; Sonoma County Regional Parks; and Sonoma Land Trust. Thanks especially to all the private landowners who graciously allowed me on their property, and more often than not, gave me a tour and some lemonade, and treated me to good conversation. Many people generously helped me in a variety of ways, and I am grateful to all of them. Colin Brooks and Shane Feirer were invaluable in teaching me about GIS, and helping me in my data analysis. I literally could not have done this research without them. Per Palsbøll and Martine Berube kindly let me use their lab for my DNA extractions and genotyping, and were always available to help when I ran into v problems. I am also deeply indebted to Bob Stafford of the California Department of Fish and Game for his willingness to share data and his help in making sure I had the information and access I needed for the kit fox project. His infectious enthusiasm and broad knowledge about