UC Santa Cruz

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.