Dolphin Tales: Good night dolphins
I always wondered where dolphins sleep at night. Do they go into the mangroves where it is shallow and more protected? Well, it seems that in some cases they do sleep on the seabed in shallow water while regularly rising to the surface to breathe, but only for a couple of hours at a time. They are often active late at night to feed on fish and squid which rise to the surface at night.
Bottlenose dolphins may also swim very slowly and steadily at the surface with another animal next to them. This is called catnapping. Adult male dolphins, which generally travel in pairs, often swim slowly side by side as they sleep. Females and young travel in larger pods. They may rest in the same general area, or companionable animals may pair for sleeping while swimming.
While sleeping, the bottlenose dolphin shuts down only half of the brain along with the opposite eye. The attentive side of the brain watches for predators and obstacles in the water. It also signals when to surface to breathe. After two hours, the dolphin reverses this process, resting the active side of the brain and awakening the rested half. The opposite eye again is active.
Other observations show dolphins resting quietly at the surface of the water, either vertically or horizontally. When a dolphin enters into a deeper form of sleep like this, mostly at night, it is called logging because in this state, a dolphin resembles a log floating at the water’s surface.
The dolphin must retain control of the blowhole to avoid drowning during sleep. The blowhole is a flap of skin on the dolphin’s head that opens and closes under the voluntary control of the dolphin. A dolphin might average 8-12 breaths a minute when fairly active and only 3-7 breaths a minute while resting.
Capt. Cathy Eagle has spent over 40 years boating in our local waters. As a professional charter captain she specializes in dolphin and nature tours. Visit CaptainCathy.com or call 239-994-2572.