Photo: Penguins Safely Lower Oxygen to "Blackout" Levels



Streams of bubbles trail behind emperor penguins diving off Cape Washington in Antarctica.

A new study of oxygen in the birds' blood vessels shows that emperors safely return from long fishing excursions under the sea ice with the lowest blood oxygen levels ever recorded in wild animals.

With such depleted reserves, experts say, other creatures would black out and suffer tissue damage.

Photograph by Doug Allen/The Image Bank/Getty Images


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