WHY does a dolphin sleep with one eye open?

Dolphins are able to sleep by alternately turning off one of their hemispheres. The other hemisphere is awake at that moment. Accordingly, one eye is open in order to monitor changes in the environment. If the right hemisphere sleeps and the left one is awake, ... Load more

Dolphins are able to sleep by alternately turning off one of their hemispheres. The other hemisphere is awake at that moment. Accordingly, one eye is open in order to monitor changes in the environment.

If the right hemisphere sleeps and the left one is awake, the right eye is open. And vice versa.