Bird Brains: Sleeping One Half at a Time
How would you like to sleep with one half of your brain asleep and the other half awake? Dolphins sleep this way. Scientists at Indiana State University have discovered that ducks sleep this way too. They have published their findings in the journal Nature, February 4, 1999, volume 397, pages 397-398.

These researchers made several observations that suggest that ducks sleep half awake so they can rest and watch for danger at the same time.

Observation #1
When ducks were placed in a row, birds at the ends of the row slept with one eye open 150% more than birds in the middle of the row.

Observation #2
Ducks at the end of the row kept their open eye away from the other birds about 86% of the time. Birds toward the center of the row had no preference which eye was open or closed.

Observation #3
Brain wave patterns (electroencephalograms) of the birds confirmed that when the ducks closed one eye, one hemisphere of the brain was asleep and the other hemisphere was awake.

Observation #4
Ducks that were half asleep escaped quickly after watching a video that looked like an attack.

These observations suggest that ducks have developed a way to sleep and look out for danger at the same time. It is still unknown if the half-asleep brain can process information.

Nevertheless, it is intriguing to think what it would be like to sleep with one brain hemisphere asleep and the other hemisphere awake. Could workers catch a quick nap and still watch for their boss coming around the corner? Could students doze off in class and still pay attention to their teachers? Interesting possibilities!

  1. Mukhametov LM, Supin AY, Polyakova IG, Interhemispheric asymmetry of the electroencephalographic sleep patterns in dolphins. Brain Res, 1977, Oct 14;134:581-584.
  2. Rattenborg, N.C., Lima, S.L. and Amlaner, C.J. Half-awake to the risk of predation. Nature, 1999, Feb. 4, 397:397-398.
  3. Rattenborg, N.C., Lima, S.L. and Amlaner, C.J. Facultative control of avian unihemispheric sleep under the risk of predation. Beh. Brain Research, 1999, 105:163-172. This is an extended, detailed version of the paper first published in Nature.

More Bird Brains.

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