Swimming

One of the largest costs to sea lions in the wild is the energy expended in swimming. Changes in the type, location, or abundance of prey items available to Steller sea lions in the wild can have significant consequences on the amount of energy needed to catch them. In order to estimate the cost of swimming, the Consortium constructed a swim mill (like an aquatic treadmill). The sea lions are trained to swim against a current with a known velocity while their oxygen consumption (energy use) is measured.

In a recently published study, Dr. David Rosen (UBC) measured how much energy Steller sea lions expended swimming at different speeds. The experiment was designed to allow scientists to estimate the cost of increased foraging or travelling on the sea lion's energy demands, and to make comparisons to other types of marine mammals.

It was quickly apparent that Steller sea lions used more energy to travel a given distance while swimming at their optimal speed than other species of marine mammals that have been studied. At first, this might seem to indicate that Steller sea lions' swimming is not as efficient as other marine mammals. However, Dr. Rosen realized that the measured cost of swimming was higher in the test animals because - being young animals - they had higher relative energy expenditures (i.e., metabolic rates) even when they were stationary.

Once these differences were taken into account, the cost of moving each kilogram of a Steller sea lion's body mass through the water was identical to most other marine mammals!

See publication: Rosen and Trites (2002)

July 17, 2002