All whales belong to a group of animals known as cetaceans , which are exclusively aquatic mammals, so the whale is a mammal and not a fish , despite some similar characteristics between these two types of animals, such as the presence of fins and their ability to swim.

In this way, whales have a series of general characteristics, such as:

• They have large dimensions : they range from about 6 to about 30 meters.
• They have weights of great tons.
• Its limbs turned into fins.
• They are long-lived.
• They do not have teeth : so they are included in the group of mysticets, which have beards. Although some cetaceans with teeth (odontocetes), are known as toothed whales, like orcas.
• They are filter feeders of small fish, copepods, krill, phytoplankton, and zooplankton.
• They often migrate long distances.

But whales, being mammals, have a series of common features with this group, let’s find out what they are:

• They have mammary glands : for the production of milk that is used to feed the young.
• They have sexual reproduction and are viviparous : that is, the young are gestated inside the mother and depend on her for their nutrition. We talk about other viviparous Animals: examples and characteristics .
• They breathe air directly from the surface : they use lungs for the gas exchange process.
• They have fat reservoirs : which are particularly larger in this group.
• At birth they have hairs that grow out.

Image: David Valencia on Reddit

The whale is a mammal because, on the one hand, it shares various anatomical and physiological characteristics with the members of this group, but additionally, molecular evidence has confirmed its evolutionary origin , which comes from terrestrial mammals.

Life originated in the ocean and that is where the deployment of biodiversity first occurs , then, when certain conditions change in the terrestrial environment, then the animals begin their transition and conquest of the latter. First, the invertebrate animals did , followed by the vertebrates, specifically those we know today as amphibians, which were the link to make the passage from the sea to the land.

In this way, the ancestors of the whales were not in the water . On the contrary, it is known that these were terrestrial animals and were located within the artiodactyl order, animals with hooves that support their weight in an even number of fingers, and where cetaceans, giraffes, camels, pigs, wild boars, hippos, among others.

This is how, millions of years ago, an ancestor that until now is estimated to be shared by cetaceans with hippos, began to change, that is, to evolve towards marine life to give rise to ancient cetaceans , which are now extinct. They left their lineage, marine mammals, which later, from evolutionary radiation, originated a division of cetaceans into the two current groups :

• Mysticeti : ​​the baleen whales.
• Odontoceti : ​​toothed whales, dolphins, sperm whales, among others.

In this sense, all the evolutionary evidence then shows that whales, despite being exclusively marine animals and unable to survive out of water, are mammals and not fish, as their anatomical, physiological, molecular or genetic characteristics confirm this.

All of the whales that exist are taxonomically grouped within cetaceans, so yes, all whales are mammals . Despite the taxonomic differences that group them into different families, genera, and species, they have a common biological aspect that makes all whales that have existed and currently exist mammals.

Let’s learn about the families of whales that exist and some of their members:

Mystics

Within the Balaenidae family we find:

• Greenland whale (Balaena mysticetus ).
• Southern right whale ( Eubalaena australis ).
• Glacial right whale ( Eubalaena glacialis )
• Pacific right whale ( Eubalaena japonica ).

The following types of whales are found in the Balaenopteridae family:

• Fin Whale ( Balaenoptera physalus ).
• Blue whale ( Balaenoptera musculus ).
• Humpback whale (Megaptera novaeangliae).

In the family Eschrichtiidae there is:

• Gray whale ( Eschrichtius robustus ).

Within the Neobalaenidae family we can find:

• Pygmy right whale ( Caperea marginata ).

odontoceti

Within the Delphinidae family we find the:

• Common killer whale ( Orcinus orca ).

In the family Monodontidae there are:

• Beluga whale ( Delphinapterus leucas ).
• Narwhal ( Monodon monoceros ).

In the Physeteroidea family we can find:

• Common sperm whale ( Physeter microcephalus ).
• Pygmy cachalote ( Kogia breviceps ).
• Baird’s beaked whale ( Berardius bairdii ).
• Northern bottlenose whale ( Hyperoodon ampullatus ).
• Tropical bottlenose whale ( Indopacetus pacificus ).
• Spade-toothed whale ( Mesoplodon traversii ).