Deep diving whale surprises scientists

2014-03-27 13:14

(Robyn Beck, AFP)

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Washington - If there were a gold medal for cetacean diving, it undoubtedly would go to the Cuvier's beaked whale.

Scientists said on Wednesday they tracked these medium-sized whales off the coast of California using satellite-linked tags as the creatures dove down nearly 2 992m and spent two hours and 17 minutes underwater before resurfacing.

Those are breath-taking accomplishments for an air-breathing creature. In fact, those figures represent both the deepest and the longest dives ever documented for any marine mammal, said Greg Schorr of the Cascadia Research Collective in Olympia, Washington, who led the study published in the journal Plos One.

"Many creatures live at the depths these whales dive to, including their likely primary prey of squid and fish. However, there is a major difference between these whales and the other creatures living deep in the ocean - the fundamental requirement to breathe air at the surface," Schorr said.

"Taking a breath at the surface and holding it while diving to pressures over 250 times that at the surface is an astounding feat," Schorr added.

Scars

By way of comparison, the record for a person holding his breath underwater is 22 minutes, according to the Guinness Book of World Records. A person, of course, would never survive the bone-crushing water pressure at those stupendous depths.

Cuvier's beaked whales are widely distributed in many deep-water regions from the tropics to cool temperate waters, though not in polar regions.

They measure up to about 7m long, with stout bodies shaped a bit like a torpedo. Their foreheads slope into a short beak with a slightly upturned mouth - leaving them with a vaguely "smiling" appearance.

Their colour ranges from gray to a reddish-brown to a pale white. Some are marked with linear white scars caused by males raking other males with their teeth, perhaps while competing for females. They feed primarily on deep-water squid and some fish near the ocean floor.

"This species is highly adapted to deep diving, spending less than two minutes at the surface between dives," Schorr said. "These are social, warm-blooded mammals that have adapted to actively pursue their prey at astounding depths - all while up to 1.8 miles away from their most basic physiological need: Air."

A number of marine mammals are known for their deep-diving abilities. The sperm whale, the largest of the toothed whales, also swims into the ocean depths to find prey. But the deep dives of sperm whales generally are less than 1km and are followed by much longer periods of time spent at the surface, Schorr said.

Elephant seals have been documented making incredibly long and deep dives. Until this new data about Cuvier's beaked whales, the records for deepest and longest dives by a marine mammal had been held by elephant seals - so named because adult males have large noses that look a bit like an elephant's trunk.

Satellite-linked tags

Elephant seals have been documented diving to depths of 2 388m and staying under water for two hours, Schorr said. But their deep dives are infrequent and followed by a comparatively long recovery time at the surface.

To track the Cuvier's beaked whales, the scientists used satellite-linked tags that provided data on the start and end times of a dive and the maximum depth of each dive, as well as the time between dives. The tags were attached to the dorsal fin using two small titanium darts.

The scientists tracked eight whales off the coast of Southern California. They were tagged in 2010, 2011 and 2012 roughly 130km west of San Diego. They amassed more than 3 700 hours of diving data.
Read more on:    marine life

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