To sleep, a bottlenose dolphin must shut down only half of
its brain, as its breathing is under voluntary control. Dolphins
take short catnaps, floating just below the surface, then
slowly rising to breathe. Often dolphins are very active during
nighttime, for some this is their main feeding time.
A dolphin's behavior when sleeping or resting depends on
the circumstances and possibly on individual preferences.
They can either:
- Swim slowly and surface every now and then for a breath.
- Rest at the surface with their blowhole exposed.
- Rest on the bottom (in shallow water) and rise to the
surface every now and then to breathe.
Generally, female bottlenose dolphins lie on the water's
surface with their blowholes exposed to the air; male dolphins
sleep just below the surface and rise to breathe periodically
as a reflex action.