Dolphins are marine mammals that need to sleep in order to function effectively. Dolphins’ sleep patterns are different from humans and other animals, as they sleep with one half of their brain at a time.
How Much Sleep Do Dolphins Need?
It’s not known how much sleep dolphins need, but they typically sleep between 7 and 8 hours a day. This is similar to the amount of sleep that most humans get on a daily basis.
Do Dolphins Sleep in Water or on Land?
Dolphins can go without breathing for long periods of time, but they still need to come up for air periodically. In order for dolphins to breathe, they must surface above the water’s surface and then return under the water once again. This means that dolphins cannot fall asleep underwater or stay asleep while submerged beneath the water’s surface. Therefore, dolphins must sleep at the water’s surface and remain there until they wake up from their rest period. When dolphins are sleeping, they often float on their sides in order to reduce drag from surrounding currents.
How Do Dolphin Brains Work?
Dolphins have brains that are very similar in size and structure to human brains. A dolphin’s brain has two hemispheres, just like humans do. Each hemisphere controls different functions of the body.
Average number of hours sleep needed by adult dolphins is 5.5 hours a day or 7.5 hours a night. Most dolphins in captivity go through periods of extreme sleep deprivation, losing up to 30% of their body weight in one month. Regularly deprived of sleep can cause various neurological problems, including: cognitive impairment, over-excitation, reduced motor function and altered brain structure.
Dolphins often sleep for 8-10 hours a day, but it’s not always easy to know how much they need. The amount of sleep that dolphins need is unproven but is generally thought to vary between 6 to 10 hours per day, exact amounts are unknown because dolphins are easy to see and observe while they sleep, so scientists can study them easily when they do sleep.
Dolphins generally sleep at night, but only for a couple hours at a time; they are often active late at night, possibly matching this alert period to feed on fish or squid, which then rise from the depths. Bottlenose dolphins, based on electroencephalogram (EEG) readings, spend an average of 33.4 percent of their day asleep. It is not clear whether cetaceans undergo dream sleep. Rapid Eye Movement (REM)–a characteristic of deep sleep–is hard to discern. But a pilot whale was noted as having six minutes of REM in a single night.
To avoid drowning during sleep, it is crucial that marine mammals retain control of their blowhole. The blowhole is a flap of skin that is thought to open and close under the voluntary control of the animal. Although still a matter of discussion, most researchers feel that in order to breathe, a dolphin or whale must be conscious and alert to recognize that its blowhole is at the surface.
Humans, of course, can breathe while the conscious mind is asleep; our subconscious mechanisms have control of this involuntary system. But equipped with a voluntary respiratory system, whales and dolphins must keep part of the brain alert to trigger each breath.
Other methods help marine mammals to hold their breath longer than other types of mammals can. Marine mammals can take in more air with each breath, as their lungs are proportionately larger than those in humans. In addition, they exchange more air with each inhalation and exhalation. Their red blood cells also carry more oxygen. And when diving, marine mammals’ blood travels only to the parts of the body that need oxygen–the heart, the brain and the swimming muscles. Digestion and any other processes have to wait.
Dolphins are marine mammals that live in oceans and seas around the world. They breathe through blowholes, feed their young with milk, and give birth to live baby dolphins. Although they are mammals, dolphins spend much of their time in the water. Dolphins sleep with one half of their brain while the other half stays awake to look out for dangers.