Posts Tagged ‘unihemispheric slow wave sleep (USWS)’

Sleep With One Eye Open

Saturday, July 30th, 2011

A group of killer whales that were hugging the coastline came into sight as we rounded the southwestern end of Henry Island. Cappuccino (K-21), one of the mature males of K pod, was spotted with his open saddle patch. Within the first ten minutes two mature orcas spyhopped, bringing half of their bodies above the surface, and there were a few lobtails from the juveniles. Then all activity ceased as they slipped into resting with a typical tight, slow moving formation. The mood was tranquil as dorsal fins of all shapes and sizes broke the surface in unison and the orcas took a lingering breath before sinking back into the Salish Sea.

Resting, or unihemispheric slow wave sleep (USWS), is when only one of the cerebral hemispheres engages in sleeping and one eye remains open. This form of sleep occurs in all the species within the Cetacea order, along with various marine mammals and birds.

Kirsten, naturalist