Recent declines in Arctic sea ice have been linked to reductions in body condition, survival, and population size of polar bears (Ursus maritimus) in some regions of the Arctic. Reduced foraging opportunity is hypothesized as the primary mechanism of sea-ice linked declines, but increased energy expenditure, as a result of changing sea ice composition and extent may be an additional underlying mechanistic factor. Field metabolic rates of polar bears have been previously unknown and limited information has existed on foraging or other behaviors in polar bears while on the sea ice. Such data are increasingly needed to better understand polar bear habitat use and improve projections of the effects of climate change on global polar bear populations. The primary objectives of this work were to: 1) develop metrics to remotely quantify wild polar bear foraging rates and behaviors; 2) measure the energetic costs of resting, walking, and swimming in captive polar bears, to better estimate the energy demands of free-ranging polar bears; 3) measure the field metabolic rates, behaviors, and foraging rates of free-ranging polar bears on the spring sea ice; and 4) evaluate the ability of tri-axial accelerometers to measure the energy expenditure of free-ranging polar bears. In this dissertation, I develop methods using tri-axial accelerometers to remotely discriminate the behaviors (Chapter 1) and index the energy expenditure (Chapter 5) of free-ranging polar bears. I further find that polar bears have energetic costs of walking that are commensurate with other quadrupedal mammals (Chapter 2), but appear to have high energetic costs of swimming similar to other semi-aquatic mammals (Chapter 3). Additionally, similar to other large carnivores, polar bears have high resting metabolic rates and high field metabolic rates (Chapter 4). Of nine polar bears monitored on the spring sea ice of the Beaufort Sea, five of these bears had energy deficits as a result of their high energy demands and low foraging success (Chapter 4). These findings highlight the physiological constraints of these large apex carnivores and reinforce their reliance on energy-dense pagophilic seal prey. Furthermore, these findings elucidate the implications of increases in the frequency of spring fasting on polar bear body composition. Given their large body size and hypercarnivory, polar bears appear to be poorly suited to cope with rapid environmental change. The metrics developed in this dissertation provide a framework to monitor polar bear behaviors and energy expenditure to aid conservation and management of the species.

Each year, marine mammals are exposed to increasing levels of anthropogenic disturbance. Some disturbances, such as boat strikes and entanglement, directly impact animals through injuries and mortality events. However, indirect effects from disturbances including over-fishing, noise and environmental pollution, declining sea ice cover, and changes in coastal habitats can have significant, though less apparent, impacts as well. These can affect both individuals and populations through declining prey availability, decreased reproductive and juvenile success, declines in body-condition, and increased mortality. Unfortunately, as a result of their cryptic lifestyle, it is difficult to measure the impact of these disturbances on many marine mammal species or predict how they will affect individuals or populations in the future. A better understanding of both maintenance and locomotor energetic demands for these species is needed to quantify the impacts of these disturbances, model the future effects, and predict the capacity of these species to adapt or respond.

Using open-flow respirometry and submersible accelerometers, I undertook a comparative physiological study examining four marine mammal species from three different groups. In Chapter 1, I studied the interaction between maintenance and locomotor costs in two coastal marine mammal species living in tropical and subtropical environments, West Indian manatees and Hawaiian monk seals. Although these warm water species exhibited a lower resting metabolic rate (RMR) than their cold-water relatives, I found that this does not confer an energetic advantage during locomotion for these species due to decreased metabolic variability. In Chapter 2, I measured RMR and locomotor costs in beluga whales as the first step towards creating a population consequences of disturbance model to aid conservation of the Cook Inlet beluga whale population. Despite variation in previous metabolic measurements of this species, the measured RMR in this study was consistent with the predicted value for similarly sized marine mammals. Analysis of locomotor costs also demonstrated a marked decrease in aerobic dive limit resulting from high speed swims commonly observed in marine mammals following disturbance. In Chapter 3, I examined and compared the relationships between locomotor metrics and the energetic cost of submerged swimming in Atlantic bottlenose dolphins, beluga whales, and West Indian manatees. This defined predictive relationships between oxygen consumption and multiple accelerometer metrics for continued collection of physiological data in both the study species and similar species in the wild.

Ultimately, these chapters provide novel information regarding the interaction between maintenance and locomotor costs in diving marine mammals, determined energetic costs to aid in the conservation of an endangered marine mammal population, and calibrated techniques that will allow future physiological study of marine mammals in the wild.

In the following chapters the interaction between large body size and climate and the resulting influence of this interaction at the level of the tissue, the whole body, and at the landscape level are investigated. In chapter one, tissue level adaptations of Asian (Elephas maximus)(Loxodonta africana)oC range of ambient temperatures were used to construct climate dependent thermal and water budgets. In chapter three, these budgets were used to construct a coupled biophysical and dynamic programming model to investigate how climate together with thermal, water, and energy demands, interact to produce landscape level patterns of habitat use. At the tissue level, the integument of elephants has a high water and low lipid content and its thermal conductivity (0.19±0.01 to 0.23±0.13 W m-^-10C) approaches the upper limit of previously measured mammalian values. The integument's resistance to water loss is also low and is comparable to or less than that of some amphibians. At the whole body level, low integumental resistance results in high rates of cutaneous evaporative water loss (E.m.: 0.31 and 8.9 g min^-1m^-2; L.a.: 0.26 and 6.5 g min^-1m^-2) and at temperatures between 28-30^oC, elephants are fully dependent on evaporative cooling to dissipate heat produced from resting metabolism. At the landscape level, simulations under six combinations of climate and primary productivity demonstrated that under cool and moderate climates, primary productivity was the strongest determinate of home range size, however, at temperatures above 24-27^oC, ambient temperature was limiting as elephants were more tightly tethered to water with less access to food. Climate appears to have a non-linear influence on landscape use because evaporative cooling increases exponentially with ambient temperature. Although the drivers of landscape use by large herbivores are complex, the results of this work demonstrate the importance of interactions between body size and climate spanning three levels of biological organization, in setting the fundamental spatial and temporal patterns of landscape use reported for elephants.

Members of the family Canidae (e.g. foxes, coyotes, wolves, dogs) are among nature’s most elite endurance athletes. To support their cursorial lifestyles, large canids achieve aerobic metabolic rates nearly three times those of similarly sized mammals and can play crucial roles in the structure and function of ecosystems. Fortunately, the field of animal energetics unites physiology and ecology by providing a common currency that links the performance of individuals to their interactions with the surrounding environment. Yet quantifying animal activity patterns and energy demand in the wild has been historically challenging, particularly for wide-ranging large canids. As a result, we are often left with in an incomplete understanding of the interplay between physiological and environmental factors driving movement, foraging, and ultimately population persistence in these species. In this dissertation, I present a laboratory-to-field approach for integrating behavioral and physiological data to forecast the resource demands required for survival by these highly mobile predators. In my first data chapter (Chapter 2), I utilize biomechanics, kinematics, and energetics to quantify the effects of domestication and selective breeding on locomotor gait and economy in canids, using several dog breeds as a model. I find that in addition to their close genetic and morphological ties to gray wolves, northern breed dogs have retained highly cursorial kinematic and physiological traits that promote economical movement across the landscape. Taking these lab-derived parameters into the field, in Chapter 3 I investigate the impact of maximal performance parameters (e.g., speed, acceleration, maneuverability) on real-time chase outcomes of large canids and felids. Using hounds (as a proxy for wolves) to recapture pumas, I reconstruct pursuit and evasion tactics by each species to identify both physiological constraints and adaptive strategies that ultimately facilitate the coexistence of these species in the wild. Finally, in Chapter 4 I measure free-ranging travel patterns and their costs in Alaskan wolves over 8 months after calibrating accelerometer- and GPS (Global Positioning System)-equipped collars on captive conspecifics. I demonstrate that activity and energy expenditure in wolves is highly varied across the Denali National Park & Preserve, reflecting regional habitat and prey heterogeneity. Ultimately, these chapters provide novel insight into how the elevated energetic demands of canids influence their ability to structure the ecological communities they inhabit. Although the drivers of activity and predation by canids are complex, the results of this work demonstrate the capability of animal-born technology to identify instantaneous to seasonal-scale patterns in energy expenditure and its role in shaping moving ecology and species interactions.

The integration of physiological and behavioral studies can yield valuable information important to the conservation and management of imperiled species. In the following chapters, I examine a suite of physiological characteristics and behavioral attributes of southern sea otters (Enhydra lutris nereis) across a variety of life stages and discuss resulting population level consequences in this threatened species. In my first data chapter (Chapter 2), I use open-flow respirometry to determine age- and activity- specific metabolic rates of immature southern sea otters throughout ontogeny. These data are then combined with activity budgets of wild sea otters to determine the energetic cost of pup rearing for adult females. In Chapter 3, I determine age-specific oxygen storage capacity and diving abilities of sea otters from birth through adulthood. Finally, in Chapter 4, I examine the foraging behavior of sea otters off the coast of central California. I found that sea otter pups have elevated mass-specific metabolic rates in comparison to adult conspecifics, which are highest for molting pups and begin to approach adult levels around the average age of weaning (6 mo.). In addition, immature sea otters have limited blood and muscle oxygen stores throughout dependency, which result in a limited capacity for diving and high dependence on adult females throughout lactation. The high energetic demands of pups result in elevated field metabolic rates (FMR) for lactating females. Female FMR is increased 17% by three weeks postpartum and continues to increase throughout lactation. By the average age of weaning female FMR is increased 96% above pre-pregnancy levels. These heightened energetic demands are reflected in the foraging behavior of wild sea otters. Adult females appear behaviorally constrained by dependent young during an already energetically costly life stage. Both physiological and behavioral data suggest that it takes sea otters approximately two years to develop comparable diving abilities to adults; however, individuals at this stage are likely inefficient foragers when compared to adults. Together these data indicate that late-lactation and the first years post-weaning are the most physiologically challenging life stages for sea otters and that these groups are likely the most sensitive to disturbance and resource limitation. The high energetic demands of dependent pups influence body condition, parental provisioning strategies, and life history decisions in adult females. In addition, high energy demands, physiological limitations, and behavioral naïveté make maintaining positive energy balance difficult for juvenile and sub-adult sea otters. Ultimately, these chapters provide novel information regarding age-specific energy demands, physiological abilities, and foraging behavior of southern sea otters across a variety of life stages, and elucidate mechanisms underlying current population level trends.

Metabolic energy demand is both a cause and consequence of how animals interact with their environments. Describing patterns of metabolism and understanding the drivers underscoring those patterns have been long-standing goals of biology for almost a century. Mammals are often the subject of comparative metabolism studies, and it is clear that their metabolic rates are determined by a complex interaction between a host of morphological, ecological, behavioral and evolutionary factors. In contrast, metabolism is often considered to be less complex for marine mammals, that is, uniformly high across all groups. This perception is the result of a paradigm that took root when determinations on marine mammals were relatively rare, and it has persisted despite a growing number of studies reporting low to moderate metabolic rates in some species.

In the following chapters, I describe the foraging energetics of free-swimming northern elephant seals (Mirounga angustirostris) and show that these seals have extremely low field metabolic rates (FMRs) that do not conform to traditional expectations for marine mammals. I also demonstrate the effects of body size and reproductive status on the bioenergetics of this species, showing that larger, fatter, pregnant seals have lower FMRs and higher foraging success. I also am able to demonstrate the importance of locomotory efficiency in maintaining a low FMR: seals responded to artificially increased locomotion costs by increasing their swimming efforts, thereby increasing FMR and lowering foraging success. These results demonstrate the sensitivity of elephant seals to anthropogenic disturbance in important foraging grounds, and potentially along migration corridors.

These results also demonstrate an energy economy strategy in a species that, by virtue of its shared environment with other marine mammals, would traditionally be predicted to have an elevated metabolic rate. In my last data chapter, I revisit the paradigm underscoring these traditional predictions. I synthesize all mammalian metabolic determinations published to–date and am able to show that the metabolic rates of marine mammals are comparable to those of terrestrial mammals, particularly when they are compared to other carnivores. I also discuss the importance of differences between the various marine mammal groups in their ecologies, behaviors and evolutionary histories in determining metabolic energy demand. These results suggest that metabolism in marine mammals is as complex as in other mammals, and that the assumption of one uniform, high–energy group is not supported by the data. This has important implications for managers interested in predicting the prey requirements of these upper trophic level predators, as traditional models are likely to exaggerate the impact of many species on their environments.

Wild animals have evolved extreme physiological adaptations to balance the risks of starvation, predation, and exhaustion. Sleeping animals sacrifice food while vulnerable to predators. Marine mammals at sea balance the need to feed with the added challenge of surfacing to breathe, where predators lie in wait. Northern elephant seals (Mirounga angustirostris) travel thousands of kilometers, performing long dives to gather sustenance before returning to land to fast while they breed or molt. For my dissertation, I engineered a device that measures when, how, and how much these animals sleep at sea- the first recording of sleep in a wild marine mammal. Across their amphibious habitat, seals slept as much as 14 hours per day on land in the lab and as little as 0 hours per day at sea. Analytical methods derived from these results allow us to interpret hundreds of diving records over a 20-year dataset to find that seals sleep about 2 hours per day during >220-day foraging trips. At sea, elephant seals leverage their extreme breath-holding capacity to create a safe sleeping niche, up to 377 meters below the surface. I developed a process to transform data into animated 3D visualizations that display physiology alongside behavior. As new technology facilitates the collection of large ecophysiology datasets, we must also advance sensor technology, analytical workflows, and visualization techniques to better interpret this data. My dissertation creates and implements novel instruments and techniques that record, characterize, and visualize the physiology and behavior of wild animals to facilitate comparative neurophysiology research within conservation and translational medicine.