Whale sets new mammal depth record
A Cuvier's beaked whale has set a new deep diving record for a sea mammal by plunging nearly two miles below the ocean surface.
The creature was one of eight whales studied off the coast of southern California whose movements were tracked by satellite-linked tags.
Scientists recorded a total of 1,100 deep dives averaging 0.87 miles in depth. The deepest was one that descended a distance of almost two miles, and the longest lasted 137 minutes.
The dives broke the current records for sea mammals set by the southern elephant seal of 1.5 miles and 120 minutes.
Two miles down, the water pressure is equal to 320 atmospheres - a crushing 4,707 pounds per square inch.
Lead scientist Dr Gregory Schorr, from the Cascadia Research Collective, a non-profit organisation based in Washington, US, that studies marine mammals, said: "It's remarkable to imagine these social, warm-blooded mammals actively pursuing prey in the darkness at such astounding depths, literally miles away from their most basic physiological need: air."
Cuvier's beaked whales are distributed around the world, and are famous for their diving ability.
Previous studies recording long-duration dives of more than a mile had indicated that the species might be the most extreme air-breathing diver in the ocean.
Unlike its deep-diving rivals, the elephant seal and sperm whale, the Cuvier's beaked whale does not need a long recovery time after extended periods at the bottom of the ocean. It averages less than two minutes at the surface between dives.
The new study, published in the online journal Public Library of Science ONE, provides a better understanding of the diving behaviour of Cuvier's beaked whales, according to the authors.
The species accounts for 69% of reported marine mammal strandings associated with military sonar operations.
However, all eight whales studied were tagged on a US Navy sonar training range off the California coast and spent a significant portion of their time there.
This suggests the Cuvier's beaked whales in this locality may have learned to cope with the kind of human disturbance that has led to strandings elsewhere.
In addition to the deep dives, the scientists recorded data on 5,600 shallow dives made by the whales, averaging about 0.17 miles.