Energetics of rest and locomotion in diving marine mammals: Novel metrics for predicting the vulnerability of threatened cetacean, pinniped, and sirenian 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