Many ecosystems, including California’s Mediterranean ecosystem, are fire-adapted. However, climate change and other anthropogenic effects are changing fire regimes, which may have implications for fire effects on natural ecosystems, including how wildlife recovers following fires. Although many studies have looked at the fire effects on vegetation, few have looked at mammal recovery, and fewer have investigated the compounding effects of an urbanized, fragmented habitat. We used camera traps and dynamic occupancy modeling to quantify medium to large mammals occurrence in the Santa Monica Mountains and Simi Hills over time. We investigated how occupancy varies relative to whether a site was burned in the Woolsey Fire, the proximity of development, and the distance to the burn perimeter. Distribution relative to the burn area and urbanization were distinct to each target species, calling for equally distinct and likely multiple management practices to conserve these species.

Urbanization has profound ecological impacts that reach beyond city boundaries. Obvious ecological consequences of urbanization include habitat loss and fragmentation. Anthropogenic barriers reduce habitat connectivity, impede gene flow between populations and accelerate the loss of genetic diversity in populations due to drift. Urbanization may have also cryptic consequences such as the effects of human-introduced toxicants on wildlife populations. Toxicants are a leading cause of population decline for a variety of animal species worldwide and may directly threaten animal populations by causing direct mortalities, or indirectly through sublethal, chronic effects such as reproductive impairment, decreased immune competence, and increased disease susceptibility or emergence. If population-level impacts occur as a result of toxicant exposure, genetic consequences may also accompany reduced population sizes and connectivity. These include inbreeding depression that may increase the probability of population extinction and the loss of adaptive potential that reduces the ability of populations to respond to novel selection regimes. Overall, urbanization presents wildlife with many novel stressors to which they must adapt or perish. Urbanization is increasing at an unprecedented pace; understanding both the obvious and the cryptic threats to wild animal populations persisting near urban areas will be vital to promoting conservation and the maintenance of global biodiversity.

To address the consequences of urbanization on wildlife populations, I focused on a well-studied population of bobcats (Lynx rufus) living in and around Santa Monica Mountains National Recreation Area (SMMNRA). This region comprises a collection of protected park areas near downtown Los Angeles. Bobcats inhabiting SMMNRA have been monitored by National Park Service (NPS) biologists since 1996. Within a localized region of SMMNRA, the NPS has demonstrated that a major freeway (US-101) acts not only as a barrier to movement for bobcat and coyote (Canis latrans) populations, but potentially also as a social barrier. Further, from 2002-2005, a notoedric mange epizootic associated with secondary anticoagulant rat poison exposure was the greatest source of mortality for bobcats. During this period, the annual survival rate for radio-collared animals fell by > 50% and in 2003 the mange mortality rate reached a high of 51%. Long-term samples were collected from this population from 1996-2012, allowing the rare opportunity to make direct comparisons before, during, and after the population decline.

Using these data as a foundation, my research focused on three main objectives. First, I characterized neutral and adaptively relevant genetic diversity in bobcat populations across SMMNRA in both fragmented urban and protected natural areas. Second, I examined anticoagulant rodenticide exposure in bobcats across southern California, contrasting seasonal, demographic and spatial risk factors in both natural and urbanized areas. Third, I characterized physiological and immunological parameters in bobcats across SMMNRA to evaluate the effects of disease and toxicant exposure on bobcat health in an urban, fragmented landscape.

I found that two freeways are significant barriers to gene flow. Further, the 3-year disease epizootic, associated with secondary anticoagulant rodenticide exposure, caused a population bottleneck that led to significant genetic differentiation pre- and post-disease populations that was greater than that between populations separated by major freeways for > 60 years. However, balancing selection acted on immune-linked loci during the epizootic, maintaining variation at functional regions. With respect to anticoagulant rodenticide exposure, I detected high prevalence of exposure (89%, liver; 39%, blood) and found that for individuals with paired liver and blood data (N = 64), 92% were exposed most frequently to greater than or equal to 3 compounds. Prevalence and the amounts of contaminants were associated with human activities that included commercial, residential, and agricultural development. I found a strong association between AR exposure to greater than and equal to 0.25 ppm or greater than and equal to 2 compounds and an ectoparasitic disease, notoedric mange. Finally, I observed that AR exposure has both immune stimulatory and suppressive effects that may explain increased bobcat susceptibility to notoedric mange as a result of chronic exposure to anticoagulant rodenticides. Bobcats exposed to ARs had elevated lymphocyte, and specifically B cell counts, and decreased percentages of neutrophils. Overall, these data highlight that even for free-ranging animals that are considered relatively adaptable to urbanization, habitat fragmentation and toxicant exposure can have profound population level effects that threaten the long-term stability of wildlife populations in an increasingly urbanized landscape.

Beginning in 1996, the National Park Service, Caltrans, and other agencies and organizations have worked together collecting, analyzing, and sharing data about regional wildlife- movement corridors within the Santa Susana Mountains, Simi Hills, and Santa Monica Mountains, near Los Angeles, California. This region is characterized by intense urban development, several major multi-lane highways, and large expanses of protected open space supporting abundant wildlife. Scientific studies include radio telemetry of coyotes, bobcats, and mountain lions, monitoring of undercrossings and culverts to evaluate wildlife utilization, assessment of wildlife mortality along selected roadway segments, and geographic information system (GIS) analyses of potential wildlife-movement corridors adjacent to and across major highways. Results from these studies demonstrate that regional wildlife viability will depend on identifying and protecting habitat linkages and wildlife-movement corridors, particularly across major highways that bisect remaining open space. In addition, the studies confirm that opportunities do exist to retain landscape connectivity, with many species found to utilize a variety of roadway-crossing structures. By combining the results of the science with transportation planning, Caltrans, the National Park Service, and other partners are now integrating on-the-ground conservation actions with needed transportation-improvement projects and regional transportation plans. Recent successes include the formation of a multi-agency and local participant group to identify and prioritize regional wildlife-movement corridors and to create plans for implementing enhancements. Agencies and organizations are also sharing information about collaborative opportunities to fund and implement wildlife-corridor enhancement projects. GIS analyses, including least-cost path-linkage analysis, have been used to identify regional wildlife-connectivity requirements. These data will then be available to help to identify priority sites for on-the-ground enhancements. Along one highway segment (State Route 23), National Park Service scientists are working with Caltrans planners and designers to install wildlife-proof fencing where mortality frequencies are high, enhance existing culverts and undercrossings to facilitate safe wildlife movement, and conduct detailed animal monitoring both before and after improvements to evaluate the success of various actions. These improvements and monitoring are all linked to lane additions along the highway to improve transportation efficiency. In another location (Highway 101), National Park Service scientists are collaborating with Caltrans environmental specialists to design and install a wildlife-crossing structure along one of the last remaining habitat linkages between the Simi Hills and the Santa Monica Mountains. Overall, we demonstrate that by sharing expertise and experiences and by linking science and planning, regional wildlife- habitat connectivity can be enhanced in combination with needed transportation projects. This model of partnership and collaboration can be applied to other areas facing similar wildlife-conservation and transportation challenges.