Dolphins are marine mammals and do not breathe underwater, They breathe consciously and need to come up for air every few minutes. generally, the question arises – do dolphins need to breathe while sleeping? How do they breathe? Where do they sleep?
Where do dolphins sleep?
Dolphins sleep near the surface of the water. They sometimes lay motionless. Other times they are seen to swim very slowly and steadily while sleeping. They come up for air in regular intervals during their sleep.
Dolphins also sleep in the seabed in shallow waters. And come up regularly for air.
Captive dolphins in SeaWorld, aquariums, etc are observed to sleep at the bottom of the pool, coming up regularly to breathe air.
Dolphins normally sleep at night and are known to enter a deeper form of sleep at night. It is called logging, as a sleeping dolphin resembles a log floating in the water.
Although they are active at late night for hunting. They sleep for a few hours at one time.
How Do Baby and Mother Dolphins Sleep?
Baby dolphins are always swimming. They are not born with enough blubber fat to float easily. So they will drown if slopped swimming. Young dolphins eat, rest, sleep while swimming all the while.
During this time, the mother also needs to swim continuously, with the young one in the tow. This is called echelon swimming. For the first few weeks, till the baby is grown enough, a mother always swims even when sleeping.
Young and female dolphins travel in larger pods. This is to ward off predators in the vulnerable state of sleep.
How Do Dolphins Breathe While Sleeping?
Dolphins need to breathe periodically while sleeping. So they sleep with only half a brain and one eye open. One hemisphere of their brain sleeps while the other half of the brain and eye remain in an alert state. So if their right brain is sleeping, the left eye stays open and vice versa.
This controlled sleep help dolphins realize the need for air and come up and breathe when needed.
This sleeping pattern is called unihemispheric sleep. And believed to have developed in marine mammals due to evolution.
They generally sleep for 8 hours a day, with each half of the brain getting around 4 hours of slow-wave sleep.
The following factors also drop the breathing requirement during sleeping.
Marine mammals have proportionately larger size lungs. Hence they can breathe in\out and exchange more air. Their red blood cells carry more oxygen. They can also switch off the oxygen requirement of certain parts like digestion etc while maintaining the flow in others.
Dolphins also have higher carbon dioxide (Co2) tolerance than humans. Unlike humans, their brains automatically do not trigger a breathing requirement.
All these factors control the air intake needed for dolphins. So their breathing rate can drop down to 3-7 times per minute compared to 8-12 times per minute while active.
How Do Dolphins Sleep Without Drowning?
It is practically impossible for adult dolphins to drown while sleeping, as they do not breathe underwater. Learning to breathe and to be able to breathe in the air is an ability newborn dolphins need to develop, else they would drown.
Marine mammals always retain control of their blowhole. They can open and close the flap of the blowhole voluntarily. According to experts, dolphins consciously can recognize when the blowhole is at the surface, to open it.
An average dolphin can stay underwater for 8-10 minutes without needing to breathe. Some dolphins are known to hold their breathes for 15 minutes while staying underwater.
How Does This Sleeping Patten Help Dolphins?
According to experts, this sleeping pattern helps dolphins in 3 primary ways.
- Controlled breathing ensures that dolohins do not drown while sleeping
- Their active half a brain looks out for danger while the other half rests. This they are always alert
- Slow swimming and some physical movement during sleep help these mammals maintain the body heat needed to survie in cold ocean.