CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Habitat Occupancy of Bobcats (Lynx Rufus) in an Urban Fragmented Landscape a Thesis Subm

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Habitat Occupancy of Bobcats (Lynx rufus) in an Urban Fragmented Landscape A thesis submitted in partial fulfillment of the requirements For the degree of Master of Science in Biology By Sean Patrick Dunagan August 2015 The thesis of Sean Patrick Dunagan is approved: _________________________________________ ______________ Dr. Paul Wilson Date _________________________________________ ______________ Dr. Seth Riley Date _________________________________________ ______________ Dr. Tim Karels, Chair Date California State University, Northridge ii Acknowledgements I would like to thank my committee members: Tim Karels, Seth Riley, and Paul Wilson. Tim shared his expertise in ecology and provided insight in the statistical design and analysis of my thesis. Seth provided logistical support needed to complete this project as well as his expertise on urban carnivores and their ecology. Paul offered his knowledge of ecology and statistics and was readily available for advice. I am grateful for the support provided by the National Parks Service. Specifically, I would like to thank Joanne Moriarty and Justin Brown for their hard work on urban carnivores. Without their work this project would not have been possible. Land use permission was provided by Conejo Open Space Conservation Agency and Rancho Simi Recreation and Parks District. iii Table of Contents Signature Page ii Acknowledgements iii List of Tables v List of Figures vi Abstract vii Introduction 9 Methods 14 Results 21 Discussion 25 Literature Cited 29 Appendix 34 iv List of Tables Table 1 – Habitat Covariates 34 Table 2 – Pearson’s Correlation Matrix of Habitat Covariates 35 Table 3 – RSF Candidate Models and Model Selection 36 Table 4 – RSF Selection Coefficients 36 Table 5 – Spearman’s Rank Correlation for 5-k Fold Cross Validation 39 Table 6 – Spearman’s Rank Correlation for Individual Bobcats 41 Table 7 – Visual Line Surveys of Cottontail Rabbits 42 v Table of Figures Figure 1 – Study Area 35 Figure 2 – Bobcat Occupancy Models 36 Figure 3 – 5-k Fold Cross Validation 38 Figure 4 – Individual Bobcat Cross Validation 40 Figure 5 – Cottontail Rabbit Fecal Pellet Counts 42 vi Abstract Habitat Occupancy of Bobcats (Lynx rufus) in an Urban Fragmented Landscape By Sean Patrick Dunagan Master of Science in Biology Urbanization subdivides natural landscapes creating isolated fragments separated by novel urban habitats. Species vary in their sensitivity to the process of urban fragmentation where some species can tolerate living in urban areas by exploiting resource subsidies. Mammalian carnivores have been shown to vary in their sensitivity to urban fragmentation where more tolerant species can exploit anthropogenic resources. Bobcats (Lynx rufus) represent an intermediate response to urban fragmentation as they are present in fragmented natural areas but do not thrive in urban development. Bobcats are known to enter urban areas and may tolerate urban fragmented landscapes by harvesting prey from urban environments. Using resource selection functions (RSFs), I modeled the habitat occupancy of 7 female bobcats in the urban fragmented landscape of Thousand Oaks, California. Occupancy models were compared to the distribution and abundance of cottontail rabbits (Sylvilagus spp.) to test if bobcats use urban areas due to an inflated urban rabbit population. Bobcats did go into urban areas, primarily at night; however, rabbit densities in urban areas varied more than rabbit densities in natural habitats. Bobcats occurred more frequently in coastal sage scrub habitats and used habitat vii edges during nocturnal hours. Rabbit densities in natural habitat patches were the most stable with highest densities in natural edge habitats. Bobcats appear to tolerate urban fragmented landscapes by behaviorally adjusting to resource distribution in natural habitat patches, and not by exploiting urban resource subsidizes. As landscapes become more urbanized, the presence of bobcats can be used to evaluate the ecological integrity of natural fragments as bobcat presence in these areas is likely not mitigated by urban resources. viii Introduction Urban development causes the loss of habitats and leaves remaining natural areas subdivided and isolated as habitat fragments. In contrast to the original natural landscape, these fragments have reduced area, distinct boundaries, and more complex shapes with higher perimeter-to-area ratios, resulting in more edge habitats (Ewers and Didham 2007). This restructuring of the landscape often causes a loss of species diversity (McDonald et al. 2008); however, some species can tolerate this change and persist in urban fragmented landscapes. Human activities in urban and suburban habitats, such as irrigation of gardens and lawns, can increase primary productivity, potentially buffering against seasonal variation, extending animal breeding seasons, and increasing the abundance of urban exploiters (Shochat et al. 2006). Whether a species can adapt or exploit urban habitats is a result of its sensitivity to these processes of fragmentation (Henle et al. 2005). This depends on how the animal views the landscape in terms of resource distribution and mortality risks, which is likely to be variable and even contradictory causing responses to be context dependent (Haila 2002; Belisle 2005). Mammalian carnivores vary in their response to fragmentation with larger species more likely to persist in large patches of natural habitat, or with increasing connectivity among smaller patches (Crooks 2002). Mountain lions (Puma concolor), which require large contiguous patches of unaltered habitat, have been shown to be sensitive to urbanization having a strong negative relationship with proximity to and intensity of urban development (Crooks 2002; Ordenana et al. 2010). Other species, such as raccoons (Procyon lotor; Prange et al. 2003) and skunks (Mephitis mephitis; Rosatte et al. 2010), tolerate or even thrive in urban habitats taking advantage of urban food resources and 9 structures (Hadidian et al. 2010). Bobcats (Lynx rufus) and coyotes (Canis latrans) represent intermediate responses to urban fragmentation (Crooks 2002), both being widely distributed in fragmented areas (Ordenana et al. 2010). Coyotes are more tolerant of urban intensity and frequent urban habitats, exploiting urban food subsidies, such as garbage, fruits, and pet food. Bobcats are strict carnivores and do not consume anthropogenic food items, but they do enter urban areas, primarily at night (Fedriani et al. 2001; Riley et al. 2003). Whether bobcats exploit food subsidies from urban environments is not well known but has been cited as an explanation for their presence in urban areas (Riley et al. 2003). Bobcats may exploit prey, such as rabbits, that might inhabit urban habitats to take advantage of lawns, gardens, and urban parks. Predator habitat selection has been linked to the hunting success associated with different habitat types (Gorini et al. 2012; Hopecraft et al. 2005). For bobcats, variation in habitat use is associated with increased abundance of prey resources (e.g. Litvatis et al. 1986; Knick 1990), which affects females more strongly than males (Benson et al. 2006; Ferguson et al. 2009). Specifically, female bobcats maintain discrete home ranges that do not overlap with conspecific females to partition resources, whereas males have larger home ranges to encompass multiple female territories to increase mating opportunities (Bailey 1974; Benson et al. 2006; Ferguson et al. 2009). Non-overlapping home range behaviors for females are adaptive to ensure that information about resource abundance and distribution does not become obsolete from harvesting by neighboring bobcats (Spencer 2012). Home range analysis is often used to assess habitat associations by animals; however, home ranges alone often misrepresent habitat relationships, especially when 10 resources are patchy. Disproportionate use of habitats by animals within home range boundaries can reveal habitat preferences or selection caused by habitat-specific differences in resource acquisition and mortality risk (Mitchell and Powell 2008; Gorini et al. 2012). Bobcats living in urban fragmented areas may receive fitness benefits from nocturnal foraging in urban habitats when perceived mortality risk is lower and if prey is available. However, bobcats do suffer mortality risks from human activities such as vehicle collisions (Riley et al. 2003) and rodenticide exposure (Riley et al. 2007), thus bobcat use of urban areas may represent a high-risk–high-reward situation where the benefits of harvesting from an inflated prey base outweigh the increased risk of perceived mortality. In the urban fragmented landscape of Thousand Oaks, California, at the border of Los Angeles and Ventura Counties, bobcat diet is primarily composed of rabbits (the desert cottontail rabbit Sylvilagus audubonii, and the brush rabbit Sylvilagus bachmani), pocket gophers (Thomomys bottae), California ground squirrels (Otospermophilus beecheyi) and rodents (e.g. dusky footed wood rat Neotoma fuscipes, desert wood rat Neotoma lepida, and various Peromyscus spp.) (Fedriani et al. 2000; Riley et al. 2010) Rabbits comprise the majority of bobcat diet, occurring three times more in bobcat scats than any other food item (NPS, unpublished data) and the consumption of rabbits by bobcats does not vary seasonally (Riley et al. 2010). Rabbits occur in both natural fragments and urban areas, and are often considered pests by residents (personal

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