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Deep Divers of the Antarctic
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16495 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
5 / 1989 |
3,543 Words |
| Author
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Randall William Davis
Randall William Davis is a senior staff scientist with Sea
World Research Institute in San Diego, California. |
"I have mentioned that the Weddell's seal during the winter
months spends most of its time in the water beneath the
ice...Again and again while setting up at night as
meteorological observers, in the silence that reigned when
others were asleep, we would hear the gurgling, bubbling,
guttural notes of Weddell's seals beneath the ship, sounds
which we knew so well from having watched the seals as they
made them."
--Edward Wilson, 1901
Edward Wilson was chief scientist and physician on Capt. Robert Falcon Scott's first polar expedition, the National Antarctic Expedition (1901-1904). He and other crew members had the unique experience of hearing the underwater vocalizations of Weddell seals through the hull of their ship, Discovery, as it lay frozen in the ice in Winter Quarters Bay at Ross Island. As Wilson noted, the seals often remain in the water for months at a time, and for good reason; the air temperature can drop below -70C, and fierce blizzards may howl for days. But in the water, the temperature is stable at
-1.9C throughout the year. Weddell seals' superb adaptations for life beneath the ice enable them to tolerate the frigid water and to breathe through holes in the ice that are little more than 10 centimeters in diameter.
Eighty years after Wilson's observations, scientists are still fascinated and amazed by the ability of Weddell seals to live year round beneath the thick, shore-fast ice that surrounds much of the Antarctic coastline. For example, when a Weddell seal dives 500 meters beneath the ice in search of fish, it must carry all of the oxygen that its tissues will require for 15 to 20 minutes. This is analogous to a person doing his grocery shopping while holding his breath. When you consider that the best human divers can hold their breath for 3 to 5 minutes and descend to less than 100 meters, then the remarkable diving ability of Weddell seals becomes apparent.
While at depth, the Weddell seal may venture hundreds of meters away from its breathing hole, which is its only access to air. If the seal is unable to relocate the hole, it will drown because it is an air-breathing
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