Penguins' super-short cat-naps – Science 1 Dec. 23, pp. 994-5 and 1026-30
Some animals sleep one half of their brain at a time – whales and sea birds who have to keep moving show this behavior. Chinstrap penguins in Antarctica have another take on this: they sleep about 10,000 times a day for an average of 4 seconds each time, on one or both hemispheres!
Paul-Antoine Libourel and colleagues from France, Germany, and South Korea ventured to the cold continent to find this out. They put small monitors on 14 penguins who were incubating eggs. The dataloggers recorded brain waves, neck muscle electrical signals (these show short bouts of nodding off), body posture, location, and any diving for food. Videos taken of some of the subjects showed visible signs – eyes closing and rapid eye movement sleep (REM). The birds slept standing or lying down.
Added up, these microsleeps gave each hemisphere of the brain about 12 hours of sleep. Other species of penguins do fragmented sleeping but for much longer intervals.
Lotsa questions here. How do they do this? How is it as effective as our long patterned sleep? Why do they need to do this? A possible explanation is that they have to keep constantly vigilant against predatory birds, the skuas. If so, it’s odd that penguins at the edge of the colony sleep in longer intervals, even though predation is more prevalent there. Maybe they have as much to worry about from neighbors, of whom there are fewer out there. We have so much to learn about sleep from our co-inhabitants of the world.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org
