You must have been surprised in your school days when you would heard about whales and Dolphins are Mammals and very similar to human except they spend there whole life in water . Have you wondered How do they sleep in water without drowning ? Or , How do they Breathe in water using there Lungs ? Or , How do they drink salty water ? since We human cant survive in salty water .
Let us find out answers one by one .
How do whales and Dolphins breathe air ?
Since Dolphins and Whales are mammals, they have lungs to breathe like humans not gills like Fish and they also cant use skin like frogs inside water to breathe .But they do need to breathe air (Oxygen) to survive .
First of all Lungs of Dolphin is larger then human and Whales have largest lung in mammals . Human beings use only quarter of their Lung capacity when they breathe while Whale and dolphins use more capacity of there Lungs. apart from that there blood can store more oxygen then human being .Finally, these animals have a higher tolerance for carbon dioxide (CO2). Their brains do not trigger a breathing response until the levels of CO2
are much higher than what humans can tolerate. These mechanisms, part
of the marine mammal diving response, are adaptations to living in an
aquatic environment and also help during the process of sleeping. Cetaceans
reduce the number of breaths they take during rest periods; a dolphin
might average 8 to 12 breaths a minute when fairly active only to have
their breathing rate drop to 3 to 7 per minute while resting.There is one more difference between human breathing and Marine mammals breathing that Humans can breathe while the conscious mind is asleep because our
subconscious mechanisms have control of this involuntary system. But whales and dolphins must
keep part of the brain alert to trigger each breath since they have equipped with voluntary respiratory system,
So Dolphins and Whales come near the surface of water for few seconds to gulf some air or we say for the process of breathing and go back inside the water for hours .
How do Whales and Dolphins sleep without drowning ?
Mammals living inside water such as whales and dolphins spend their entire lives at
sea. So how can they sleep and not drown? Observations of bottlenose
dolphins in aquariums and zoos, and of whales and dolphins in the wild,
show two basic methods of sleeping: they either rest quietly in the
water, vertically or horizontally, or sleep while swimming slowly next
to another animal. Individual dolphins also enter a deeper form of
sleep, mostly at night. It is called logging because in this state, a
dolphin resembles a log floating at the water's surface.
When marine mammals sleep and swim at
once, they are in a state similar to napping. Young whales and dolphins
actually rest, eat and sleep while their mother swims, towing them along
in her slipstream--a placement called echelon swimming. At these times,
the mother will also sleep on the move. In fact, she cannot stop
swimming for the first several weeks of a newborn's life. If she does
for any length of time, the calf will begin to sink; it is not born with
enough body fat or blubber to float easily. Lots of swimming will tire an infant, producing a
weak animal susceptible to infection or attack. 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.
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.While sleeping, the bottlenose dolphin shuts down only half of its
brain, along with the opposite eye. The other half of the brain stays
awake at a low level of alertness. This attentive side is used to watch
for predators, obstacles and other animals. It also signals when to rise
to the surface for a fresh breath of air. After approximately two
hours, the animal will reverse this process, resting the active side of
the brain and awaking the rested half. This pattern is often called
cat-napping.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.As I already discussed in previous question
Humans, 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.
How can sea mammals drink salt water ?
It unreasonable to assume that sea mammals can live on salt water any more than we can . The first thing that occurs to me is that their need of fresh water should be less then ours , because a lot of water we ingest , particularly during summer , is used to cool us through evaporation . Clearly , large sea mammals do not need this - when the skin temperature rises all they need to do is slip down into the water for a while .DOLPHINS and other sea-dwelling mammals can obtain water from their food and by producing it internally from the metabolic breakdown of food.They have there own pure water factories inside there body . Unlike Human water is not a waste product of metabolism for them .
So Unlike land mammals, sea mammals don't drink water and produce them internally or either drink very very occasionally , Since they need very less water . Apart from that some of them have specialized Kidney to adapt to salty water.
