The primary focus of our research has been the energetic requirements of foraging. Energetics is the study of how much energy an animal requires to dive, forage, grow, reproduce, and maintain its health. We have investigated the energetic costs of diving and swimming. We have compared horizontal transiting to vertical diving, active swimming to gliding, examined the optimal depth of an animal in transit, as well as studies to see if the animal’s heart rate can be used to predict how much oxygen is consumed while the animal is foraging at depth.
The animals are transported by boat to the Indian Arm fjord, where a diving platform is moored. The sea lions can surface in the center of the platform to breathe into a floating Plexiglas dome. Scientists determine how many calories the sea lions burn by measuring the concentrations of exhaled carbon dioxide and inhaled oxygen within the dome. It is the same basic technique used to assess the fitness of athletes on stationary bicycles.
The scientists create simulated “prey patches” by pumping fish down PCV tubes at different rates and to different depths. The sea lions dive to 10, 20, 30 m and deeper depths to feed. Varying the number of feeding tubes and rates and depths of feeding allows the researchers to determine the tradeoffs and energetic costs a sea lion incurs to forage optimally.
The sea lions are also great cinematographers and are providing scientists with unique and valuable insights into how they use and perceive their underwater world. Our sea lions have been using cameras attached to their harnesses to film their ocean environment and collect footage of our trials.
All of the research behaviors performed by our animals are voluntary and mimic natural foraging behaviors. Our sea lions are mentally stimulated by learning new behaviors and are taken into the open water to maintain their general fitness and strengthen the much-needed research behaviors.
Our sea lions are not tethered and are free to leave us at any time. However, our sea lions have always come back, much like a dog that is allowed to run unleashed. We assume this reflects a measure of trust and bond that has formed between us.