When emperor penguins dive below the Antarctic sea ice in search of food, they can descend five times as deep as a human and can swim on a single breath for up to 20 minutes.
Researchers are trying to find out how they manage these incredible feats to potentially help improve surgical procedures and anesthesia.
Emperor penguins are the tallest and heaviest species of penguin. During their harsh life cycle, they dwell on ice and march up to 100 miles from their mating grounds to dive into frigid waters to feed on krill and fish.
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Using small devices called time-depth recorders, researchers found that the birds could dive deeper than 1,800 feet. The deepest a human can dive unassisted is just over 300 feet.
The penguins "dove much deeper than we ever thought they would," said Paul Ponganis, a physiologist at the Scripps Institute of Oceanography in La Jolla, Calif.
Researchers aren't sure how emperors can descend so deep without developing decompression sickness, commonly known as "the bends."
"That's probably the big question about tolerating depth," Ponganis told LiveScience.
The bends is a condition that occurs in human divers in which pressurized nitrogen builds up in the blood due to gas exchange going on in the lungs.
The nitrogen expands into bubbles in the bloodstream during ascent, causing itching, pain and sometimes death.
Whales hold the deep-diving record for air-breathers, but they do get the bends, too.
Seals, which can dive even deeper than the emperors, avoid this condition because they deflate their lungs when they go down.
Ponganis said it is unlikely that emperors do this, due to the structure of their lungs.
Ponganis is also looking at how emperors can stay under water for such a long time on a single breath of air.
"They can swim and dive and function quite well when the oxygen level goes very, very low in the lungs," Ponganis said.
At the same oxygen levels, a human would go unconscious.
Compared with humans, both seals and emperors have more oxygen circulating in their blood because they have a higher blood volume and more hemoglobin, the protein that carries oxygen through the blood.
The penguins also have more myoglobin, which stores oxygen in muscle.
"When they're swimming, they have an oxygen store right there that they can use," Ponganis said.
Unlike humans, emperors decrease their heart rate when they swim, so they use up their stores of oxygen more slowly.
Ponganis is interested in how penguin physiology compensates in these conditions.
Finding out exactly how it does so could improve medical anesthesia techniques and aid research into avoiding tissue damage when the body is deprived of oxygen.
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