SANDIEGO, CA — Scientists have gained insight on deep-diving marine mammals and their ability to swim to profound depths with limited reserves of air. By attaching video cameras and other sophisticated instruments to Weddell seals hunting beneath the ice in the Antarctic, a northern elephant seal diving in Monterey Bay, a bottlenose dolphin swimming off the coast of San Diego and a 100-ton blue whale, researchers found a laid-back, energy-saving approach to diving.
Most dives began with 30 to 200 seconds of swimming, followed by a relaxed glide for the rest of the descent. "Basically, they're turning the motor on and off in the course of a dive, and that enables them to reduce oxygen consumption by 10 to 15 percent compared with what they would need if they swam all the way down," said team member Professor Terrie Williams from the University of California, at Santa Cruz. A Weddell seal performed the most remarkable feat, gliding for 6.2 minutes while descending to 1,771 feet.
Researchers were surprised at how the animals all used common tactics to go deep, even though they are very far apart on the evolutionary tree. The animals' lungs collapse progressively with increased pressure. "The mass of the animal remains the same while its volume decreases, so it starts to sink," Professor Williams explained. The research, which is published in the journal Science, was funded by the US Office of Naval Research, the National Science Foundation, and the National Geographic Society.