Animal aggregations are common in nature and directly influence important biological processes such as resource acquisition, predator avoidance, and reproduction. Yet our ability to study the behavior of animal groups with precision has been limited by the challenge and expense of tracking multiple individuals at once. As a result, the majority of knowledge about collective behaviors – particularly in large, or far-ranging species – has been derived from detailed observations of relatively few individuals (i.e. field observations or marked individuals), or theoretical simulations lacking validation in the field. While these approaches have formed the foundation of animal behavior research, they frequently suffer from an inability to generalize individual-level observations to population-level processes.

Recent advancements in high-resolution remote sensing now present exciting opportunities to overcome many of these limitations by obtaining a comprehensive view of individual behaviors and the full socio-environmental context in which they are embedded. By adapting high-resolution remote sensing technologies to study large groups of animals in the wild, I aim to examine the role of environmental and social forces in driving behavioral shifts in ungulate herds across multiple scales of space and biological organization (i.e. individuals to populations).

To accomplish this, I first establish the historical context for these new techniques by conducting a literature review of modern and historic methods for studying collective animal behavior in the field. This review outlines the strengths and limitations of such methodologies while identifying opportunities for advancement afforded by recent and upcoming technological innovations. I then demonstrate the utility of this technology by developing a new method to study the distribution and behavior of tens of thousands of animals (white-bearded wildebeest; Connochaetes taurinus) identified in high-resolution (< 50 cm) satellite imagery. This non-invasive method is directly scalable from individuals to populations and reliably predicts three behavioral states (82% accuracy overall) from a single metric of group structure (i.e. coordinated orientation). Such an advancement represents a step-change in our ability to study social processes under natural conditions and forecasted advancements in both resolution and automated image processing are likely to expand applications for this technique in the near future.

Finally, I combine these new remote sensing techniques with traditional animal tracking methods (e.g. GPS telemetry and transect surveys) to evaluate the factors that drive habitat selection by a reintroduced, free-ranging ungulate (tule elk; Cervus canadensis nannodes) in a cattle-dominated ecosystem in northern California. These analyses confirmed that reintroduced elk largely avoided areas managed for and used by cattle across all seasons. Further, the use of remotely sensed data revealed that this pattern likely resulted from differential habitat preferences rather than outright avoidance behavior. As a result, the potential for conflict between cattle and reintroduced elk is expected to be minimal in this ecosystem, and managers may continue to rely on manipulation of resources (e.g. providing artificial water sources) to limit interactions between the two species. By presenting this updated approach to the study of animal behavior, I aim to demonstrate the value of remotely sensed data for providing both basic and applied insights into the behavioural ecology of large animal systems.

Shark populations worldwide have been depleted by overfishing, yet empirical evidence of shark abundance and diversity before human impact is scarce. Without long-term data to document the timing and magnitude of shark declines, it is challenging to understand how the loss of these high-level predators has reshaped ecosystems and set meaningful management targets informed by natural variability. In this dissertation, I use fossil shark scales (dermal denticles) to reconstruct shark communities on coral reefs over the last several millennia. After finding denticles to be well-preserved in reef sediments, I refined an extraction method and built a reference collection to facilitate denticle classification. By measuring denticle shedding in captive sharks, I showed that shedding rates vary across sharks with different life modes, thereby influencing how shark communities are represented as denticle assemblages in the fossil record. I then calibrated the denticle record by comparing denticle assemblages preserved in surface sediments with wild shark populations on a remote, unfished atoll. I found that denticle accumulation rates were positively correlated with shark abundance and that denticle assemblage composition was consistent with commonly observed shark species. Building on this foundation, I recovered denticles from mid-Holocene and modern reef sediments in Caribbean Panama to define a local shark baseline before major human impact and quantify shifts in the modern shark community from this historical reference point. Denticle assemblages indicated that shark communities in this region declined threefold since the mid-Holocene and were functionally restructured by both long-term harvesting and habitat modification. Together, this work demonstrates that the denticle record can reveal changes in shark communities over long ecological timescales, helping to contextualize contemporary abundances and inform shark management and ecology.

Ontogenetic habitat shifts are a common feature of many marine species, including sharks, which face conservation threats when their distributions overlap with human resource extraction and habitat modification. White sharks (Carcharodon carcharias), for example, exhibit a distinctly coastal phase as juveniles, with a limited distribution compared to the basin-scale range of adult white sharks. Unoccupied aerial vehicles (UAVs) are a promising tool for studying coastal shark aggregations, especially in instances where sharks’ proximity to human activity has both conservation and public safety implications. In this study, we conducted UAV survey flights over a white shark (Carcharodon carcharias) aggregation site in Southern California from 2019 to 2021. We determined the density of observed individuals, their location within the aggregation site, and their body length using photogrammetry. We also determined how temporal and oceanographic factors affect white sharks at different developmental stages. We observed a year-over-year increase in the average density of white sharks. We also noted that the temporal pattern of density within each year was not consistent across years. White shark detections were much higher in the immediate inshore area of the surveyed aggregation site. The proportion of individuals ≥ 3m total length (TL) increased in 2021 relative to previous years, comprising 40% of observations - a prevalence of larger sharks higher than was previously observed at these sites. White shark density was highly variable within and across years, and more sharks were observed at later hours of the day. Sharks < 3 m TL were observed more often during periods of colder water temperature, while the density of larger sharks did not appear to be affected by water temperature. Low visibility and higher tides reduced shark density, while chlorophyll-A levels, sea state, and swell height were not associated with density. Our study highlights the dynamically variable use of near-shore habitat by this top predator and suggests that juvenile white sharks may be more responsive to changes in oceanographic conditions, namely water temperature, than larger individuals. Understanding how temporal patterns and oceanographic predictors of density change over time, and as white sharks age, can help us better predict how this species uses coastal habitats and when they may be more likely to share space with humans and be more exposed to anthropogenic threats. We demonstrated that using UAVs to monitor white shark aggregations can produce useful insights which have both pure and applied value when attempting to better understand how these and other sharks utilize these especially dynamic coastal habitats.

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.

Human-induced environmental change has affected ecosystems on a global scale, altering the ecology and evolutionary trajectories of various species. Animal behavior is highly vulnerable to shifting with human impact and shifts and individual variation in animal behavior can influence functioning of the ecosystems they inhabit. Harvest of predators, for example, can have cascading effects on the behavior of their prey as they experience reduced predation pressure. Alternatively, depletion of food sources can cause wildlife to shift their behavior to access alternative food sources. Here, I explore anthropogenic impact to animal behavior and the knock-on consequences any such changes may have on ecosystems in two different systems: shoaling fish on coral reefs and seabirds that nest on oceanic islands. On coral reefs, I explored differences in shoaling behavior of coral reef fishes on two islands whose predator populations face differing fishing intensities and shed light on the ecological role of shoaling behavior to coral reefs. Fishing of marine predators and cascading effects on marine ecosystems is of critical concern. Predators are thought to be an important reason for why fish shoal, thus, reducing predator populations could alter shoaling behavior for prey fish. I also specifically characterized movement and foraging-associated behaviors of one of these fishes in this same comparative context. My work suggests that in areas with reduced predator abundance the tendency of some, but not all, fish species to form shoals is reduced. Additionally, I found differences in movement, grazing, and interactions with heterospecific fish between shoaling and solitary fish. These observations shed some empirical light on how overfishing could affect shoaling behavior and suggests that social behavior of individual may play an important role in mediating their ecological function. On oceanic islands, I examined the effects of large nesting colonies of Western Gulls (Larus occidentalis), which are known to forage on human refuse, on the Channel Islands of California. Specifically, I explored how their foraging on anthropogenic food sources may change nutrient deposition patterns at their relatively remote and protected breeding islands. Mobile animals that traverse ecosystem boundaries can fundamentally reshape environments by providing critical nutrient and energy inputs to the ecosystems they inhabit. In particular, aggregations of seabirds often transform coastal and island ecosystems through large amounts of nutrient-rich guano deposition. Anthropogenically-driven losses of these subsidies can occur through changes in abundance of mobile species, including seabirds, and have been shown to drive whole scale ecosystem state change on islands. However, even though many species that forage on anthropogenic food sources are highly mobile and may thus play important roles in moving nutrients from urban systems to otherwise conserved ecosystems, the impacts of anthropogenic supplements to spatial subsidies have been largely ignored. I found high (up to 40%) but site-specific rates of urban foraging, resulting in between 66 and 93 kg of guano per hectare (ha) on these two sites during the breeding season, driving marked seasonal increases in soil nitrogen and phosphorus content comparable to nutrient deposition in industrial agriculture. By exploring similar facets of animal behavior in two separate systems, my research highlights the footprint that human activity can cast on even remote ecosystems through impacts to animal behavior

The brown box crab, Lopholithodes foraminatus, is a deepwater crab that is found along the eastern Pacific Coast. Historically, landings in California have been low for this species, but an increase in fishing pressure prompted the state to designate it as an emerging fishery and implement an experimental fishery program for it. With no known biological studies on brown box crab in California, gathering essential fisheries information to evaluate the feasibility of a targeted fishery is necessary. We investigated the reproductive capacity of the brown box crab in southern California. From 2018 – 2021 brown box crabs were collected monthly from fishermen. Size at sexual maturity was determined by presence/absence of mature gonads (physiological), relative growth of the chela for males and abdomen width for females (morphometric), and presence/absence of eggs on females (functional). We found that females reach physiological maturity at a carapace width between 50.8 mm and 71.7 mm, and males between 43.3 mm and 66.3 mm. Morphometric maturity analysis showed a clear inflection point of abdomen width between immature and mature females. Females were 50% functionally mature at 75 mm carapace width. Morphometric and functional maturity was not detected for males, albeit samples of small male crabs were extremely limited thus warranting further study. Females followed a biennial reproduction pattern, mating in the fall followed by an 18-month brooding period with hatching the following spring. Fecundity was positively related to size and ranged from 8,352 and 62,181 eggs per female for crabs measuring 67.8 to 130.5 mm carapace width, respectively. These findings provide biological information that can inform the evaluation of a fishery for the brown box crab, including potential management strategies and models for assessing stock condition.