Research Projects > Bioenergetic Studies with Captive Steller Sea Lions

Bioenergetic Studies with Captive Steller Sea Lions

Bioenergetic studies help quantify the energetic costs of various components of the sea lion’s energy budget, their interaction, and their changes with age.

Captive Steller sea lions are used to investigate a number of hypotheses explaining the decline of the species in the wild. This continuing project uses captive Steller sea lions in controlled empirical scientific studies, focusing on bioenergetics, nutrition, and physiology. The project estimates the cost of changes in sea lion behavior linked to changes in their biological and physical environment. The quantity and type of prey available to the sea lions are altered to study the physiological and nutritional effects of potential changes in prey type and/or availability. Possible links between changes in prey composition and sea lion health and reproduction are also explored.

Understanding the effects of changes in the physical and biological environment on an individual animal’s physiology is integral to assisting in the recovery of Steller sea lions.

Project Outline:
Four studies will investigate specific aspects of sea lion physiology, bioenergetics, and nutrition. Experiments will examine the efficacy of using heart rate as an indicator of metabolism, the effects of under-nutrition on thermoregulatory abilities and activity patterns, the role of compensatory growth in overcoming periods of under-nutrition, and the auditory capabilities of animals. A review of research with captive marine mammals as a tool for conservation will also be undertaken.

The Nutritional Stress hypothesis proposes an energetic and/or nutritional imbalance between food intake and the requirements of individual sea lions as an underlying cause for their decline. This imbalance could be caused by either a change in diet (type, quality, distribution, or abundance) and/or a change in the amount of energy required by individuals (e.g., changes in behavior, activity patterns, or environmental conditions). The potential effects of periods of under-nutrition on Steller sea lion health and physiology will be investigated by examining the effects of body condition on sea lion energy expenditures and behavior. A series of experiments will also be undertaken to examine changes in body mass, body composition, metabolism and blood biochemistry and hematology during an 8-week ‘recovery’ (mass gain) period while consuming different species of fish. The results of this study will increase our understanding of the longer-term effects of under-nutrition on Steller sea lion physiology.

Previous work with captive Steller sea lions indicated that heart rate can be used to predict oxygen consumption while fasting, but that a different relationship between these variables was produced when animals were feeding. Heart rate may still prove useful if additional physiological state indicators can be incorporated into a more complex predictor model, and the effects of feeding can be quantified and mathematically incorporated. To that end, a multivariate equation incorporating a number of behavioral and physiological parameters to more accurately predict energy expenditures from heart rate will be developed.

Another study will determine an audiogram for Steller sea lions, which is needed to assess the potential impact of killer whales and anthropogenic disturbance on sea lions. Finally, a workshop will be held with leading marine mammal physiologists to review research with captive marine mammals as a tool for conservation.

Together, these projects will help scientists understand the potential physiological mechanisms linking changes in Steller sea lion population levels to hypothesized changes in prey quality, distribution, or abundance, predation risk, and physical environmental conditions. Results from these studies will directly contribute to effective species recovery plans.

Principal Investigators:
David Rosen University of British Columbia
Gordon Hastie, University of British Columbia
Andrew Trites, University of British Columbia

Collaborating Investigator:
David Mann, University of South Florida

Funding Source:
NOAA and the North Pacific Marine Science Foundation