Steller sea lion research > Nutritional Stress >Energy Requirements > Metabolism

Measuring Energy Expenditures

To understand the relationship between food intake and sea lion health, it is important to measure the costs associated with various activities, including swimming, resting metabolism, field metabolic rate, thermoregulation, and diving.

METABOLISM

The amount of energy an animal uses can change depending on its age and the time of the year and its level of nutrition. Dr. David Rosen (UBC) has been measuring the metabolism (energy use) of the sea lions at the Vancouver Aquarium Marine Science Centre since they were pups using a number of methods.

Resting metabolic rate is a measure of an animal's basic energy use.
It is estimated by having the sea lions rest quietly inside a specially built 'metabolic chamber', and measuring the amount of oxygen the animal consumes, and the amount of carbon dioxide produced. As with most mammals, the sea lions show large changes in metabolism with both age and season.

 

Metabolism can also be estimated via the animal’s heart rate. Studies with the captive Steller sea lions compared measurements of metabolism simultaneously obtained from oxygen consumption and heart rate. The study concluded that heart rate was a good estimator of energy consumption when the animals were fasted, but not as good when the animals had been fed. Further studies are trying to improve these predictions.

 

 

 

 

Metabolism over a long period (such as field metabolic rate) can also be estimated by the disappearance of injected doubly labeled water.

A study run by Dr. David Rosen (UBC) and Dr. Russel Andrews (UAF) used a specially-designed large metabolic chamber to test this method in Steller sea lions. The energy expenditure of the sea lions was simultaneously measured from oxygen consumption and doubly-labelled water, and the results used to evaluate the accuracy of the method.

 

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