Like any mammal, the dolphin must sleep. It sleeps frequently throughout
the day in short periods to accumulate a total of about 8 hours of rest per day. A dolphin will sleep in one of three
general manners: (a) near the surface with its blowhole exposed (as in the above video), (b) resting on the bottom of
its environment, rising occasionally to breathe, or (c) swimming in a slow circle called "pattern' or "stereotypic" swimming,
as seen in the following video.
Its breathing is voluntary (it must remind itself to breathe, unlike the human who can breathe while totally
unconscious), and would drown if it went into REM (rapid eye movement, or deep) sleep. Thus, the dolphin's brain must remain
alert enough during sleep to continue to breathe. Verified by EEG (electroencephalogram) testing examining its brain
waves, it does this by "shutting down" half its brain. The hemisphere that is shut down rests, while the half that is not
remains alert for predators (in the wild) and reminds the animal to breathe. No known land mammal is capable of simultaneous
sleep and visually coordinated motion at the same time. As the left side of the brain controls the right-sided body activities
and vice-versa, the dolphin sleeps with the eye shut opposite the side of brain that is resting; this feature is called "cross-ocular
Research has shown that captive
dolphins tend to sleep more often during the night and at the surface than wild dolphins do. In captivity, the interruption
of day time sleep opportunities due to interaction with animal care workers and the public probably accounts for this difference
in sleep patterns.
For information regarding sleep in the newborn calf and its mother,
see the "Mother & Calf" section on this site.
Understanddolphins.com contains information condensed from a number of reputable technical sources,
peer reviewed journal articles, and respected dolphin research facilities, as well as from my personal experiences and
observations as a dolphin VIP Tour Guide and Educator.
I have made every attempt to support the information presented in this site with video and still
photographic images. On a regular basis I plan to produce more of these images and will continue to update the site with these
as well as with any new and scientifically verified information which becomes available.