The penguins in this study rely on extremely short naps.
Cumulatively, the animals slept about 11 hours per day.
The researchers noted that mallard ducks will sleep with both eyes closed when safely surrounded by fellow birds.
A chinstrap penguin nodding off.Photo:Paul-Antoine Libourel
More:What Do Animals Dream About?
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An incubating chinstrap penguin.Photo:Won Young Lee
