Why Do Whales Live In Water If They Don’t Have Gills?

Whales live in water despite not having gills because they have evolved over millions of years from ancestors who lived on land. Their ancestors with lungs adapted very little by little to the water.

Whales have evolved from land mammals to marine mammals. Its physiognomy was adapting to be able to live under water. 

The fossils discovered show how cetaceans evolved from artiodactyls, about 50 million years ago.

The teeth of this creature indicate that they preferred land plants to fish, which is a sign that the evolution towards the water was probably to get away from predators rather than to look for food.

Humans are mammals too. Mammals are the group of animals that breathe air through their lungs and raise their children with mother’s milk.

How do whales breathe?

All animals, including humans, need oxygen, a chemical found in air and water. Fish use their gills to take oxygen from the water in which they live.

In contrast, whales, being mammals, use their lungs to breathe air and can stay underwater for long periods of time.

That is one of the reasons why whales go to the surface of the ocean. Sometimes they can be seen on the surface of the water with only part of their back sticking out.

Unlike other mammals, whales do not have a nose. Instead, they have spiracles (like nostrils) on top of their heads.

Sometimes when a whale expels air from the hole in their head, they expel water that often includes mucus and gush out.

The spiracles are made up of muscles that keep the orifices closed when the whales are underwater and open when the animal is on the surface and needs to breathe.

After exhaling air, they inhale fresh air into their lungs. The humpback whale’s lungs can hold up to 5,000 liters of air.

This is because a whale’s heart can weigh between 180 kg – 200 kg. It is 640 times bigger than a human heart. The blue whale’s heart is the largest of any animal.

Unlike humans, whales breathe voluntarily.

How do whales sleep?

Although knowledge about sleep in wild whales is limited, captive whales have been observed to rest one brain hemisphere while the other remains active.

This allows them to continue swimming, breathe consciously, and avoid contact with other species during their resting period.


  1. Nature. (sf). The land-based ancestor of whales . Retrieved from nature.com
  2. Nmlc. (sf). How do whales breathe . Retrieved from nmlc.org
  3. Wdc. (sf). How do whales breathe . Retrieved from uk.whales.org
  4. Wikipedia. (sf). Balaenidae . Obtained from es.wikipedia.org
  5. Wikipedia. (sf). Evolution of cetaceans . Retrieved from en.wikipedia.org
  6. Wikipedia. (sf). Whale . Retrieved from en.wikipedia.org.

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