Behavioural and ecological energetics of elasmobranchs

Evan Edward Byrnes

Understanding the capacity of animals to behaviourally and physiologically cope with environmental change is becoming crucial for developing process-based approaches to wildlife management. Energy is one of the most basic resources of animals, and the need to acquire energy to fuel daily activities, growth, and reproduction drives many aspects of ecology. Decades of comparative physiology work have shown the metabolic rates of animals systematically vary based on a suite of organismal traits and environmental factors. However, it is poorly understood how such metabolic variation influences animal’s behaviours in the wild, and as such, their capacity to adapt to environmental change. Recently, novel technologies have allowed physiological research to be conducted in the field, facilitating investigations of how animal physiology drives the behaviours of animals in natural settings. In this thesis, I present a number of studies that investigate how the three primary factors governing the physiology of ectotherms, namely body size, temperature, and habitat shape an animals’ capacity to cope with anthropogenic threats and environmental change. Using a combination of respirometry experiments, on-animal motion-sensing, biotelemetry tracking tools, and sophisticated behavioural modelling, I examined how changes in metabolism drive the behavioural and spatial ecology of sharks. First, I demonstrate how local environmental pressures place constraints on a species ability to expand home ranges to escape local resource limitations. Second, investigations of the drivers of behavioural and activity patterns of sharks revealed that within these spatial constraints, sharks’ ability to adjust their foraging and resting patterns are relatively limited. While metabolic changes associated with increased environmental temperatures pressure sharks to forage more often, functional traits limit their ability to forage outside short temporal windows. Taken together, these results indicate that physiological requirements place substantial constraints on the behavioural flexibility of sharks, which will likely have serious impacts on their life history, fitness, and survival in the face of continued environmental change. Lastly, I discuss the implications of physiological and behavioural constraints for the management of threatened shark populations

Behavioural and ecological energetics of elasmobranchs

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