UC Santa Barbara

The spread of human development has modified ecosystems around the world. Very little habitat remains unmodified, and regions experiencing large-scale alteration continue to grow. Mammals display a range of responses to human development; sensitive species often decline or disappear in areas with high anthropogenic change and tolerant and/or adaptable species can increase and even thrive in human-modified habitats. Many human activities can significantly alter habitat, including agriculture, pollution, urban development, roads, and the introduction of invasive species. This dissertation aims to examine how two major categories of anthropogenic habitat change – invasive species and urbanization – impact mammal habitat use, diet, and movement behavior. Invasive plants can significantly alter ecosystems, decreasing their suitability for native species. The invasive plant Arundo donax is known to be low quality habitat for birds and invertebrates, and it is a major threat to southern California riparian ecosystems. I investigated the impact of Arundo on mammalian carnivores, such as coyotes, bobcats, raccoons, and striped skunks, near the Santa Clara River, California, using remote cameras placed in locations with varying proportions (high to low density) of Arundo. I compared the camera detection rate of all mammalian carnivores between the three habitat types to determine habitat use and occupancy. To understand the mechanisms behind changes in habitat use, I also live-trapped small mammals in each habitat type. The results showed that mammalian carnivores preferred native habitat over habitat with more Arundo, but small mammals did not show the same preference, indicating a mechanism other than food availability as the cause of the carnivores’ avoidance of Arundo. Heavily human-modified habitat, such as urban areas, can be detrimental for many mammal species but can also provide advantageous resources that allow other mammals to flourish. To learn more about these synanthropic mammals, I compared the diet of raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), and striped skunks (Mephitis mephitis) through time in urban Santa Barbara County using carbon and nitrogen stable isotope analysis. I compared the isotopic niche breadth and proportion of anthropogenic food throughout a period of urban growth (1946-2019), and I found that of all three mesopredators, raccoons were the only species that experienced a significant shift toward anthropogenic food over time. Additionally, I examined the movement behavior of raccoons near the University of California, Santa Barbara, campus using high resolution GPS data. The movement data elucidated patterns of raccoon behavior across the urban landscape: raccoons prefer denning in undeveloped spaces, are more likely to be foraging in developed spaces, and select for dumpsters, herbaceous habitat, and high and medium intensity developed habitat. Gaining insight into the ways by which mammals are impacted by large-scale anthropogenic modification to their habitat can help to improve management plans for sensitive and synanthropic species and, ultimately, lead to increased potential for long-term coexistence between humans and wildlife.