All living beings on the planet have their origin in the aquatic environment. Throughout evolutionary history, mammals have been changing and adapting to the conditions on the surface of the earth until, several million years ago, some returned to submerge in the oceans and rivers, adjusting to life under these conditions.
In this article on our site we will talk about aquatic mammals, better known as marine mammals, since it is in the seas where the largest number of species of this type inhabit. Discover the characteristics of these animals and some examples.
Characteristics of marine mammals
Aquatic mammals, like other mammalian animals, are characterized by having mammary glands that produce milk for their young, as well as like sweat glands. Likewise, they gestate the fetuses inside their body. However, these are not the only characteristics that these species present.
The life of mammals in the water is very different from that of land mammals. In order to survive in this environment, they must have acquired special characteristics during their evolution. Water is a much denser medium than air and also offers greater resistance, which is why aquatic mammals have an extremely streamlined body that allows them to unfold easily. Developing fins similar to those of fish has been a significant morphological change. It allows them to increase speed, direct swimming and communicate.
Water is a medium that absorbs much more heat than air, which is why marine mammals have a thick layer of fat under a hard and robust skinthat keep them insulated from these heat losses. Likewise, it serves as protection when they live in very cold areas of the planet. Some marine mammals have hair because certain vital functions are carried out out of the water, such as reproduction.
Those marine mammals that, in certain periods of their lives, live in great depths, have developed other organs to be able to live in the dark, such as the sonarThe sense of sight in these ecosystems is not useful, because sunlight does not reach that depth.
How do aquatic mammals breathe?
Aquatic mammals need air to breathe. Therefore, they take in large amounts of air and hold it inside their lungs for long periods of time. When they submerge after taking a breath, they are able to redirect blood to the brain, heart, and skeletal muscle. Your muscles have a high concentration of a protein called myoglobin, capable of accumulating large amounts of oxygenIn this way, marine mammals are able to remain for considerable periods of time without taking a breath.
Young and newborn pups have not developed this ability, so they will need to take a breath more often than the rest of the group.
Types of marine mammals
Most species of aquatic mammals live in the marine environment. There are three orders of marine mammals: cetacea, carnivora and sirenia.
Aquatic mammals of the order Cetacea
Within the order Cetacea, the most representative species are whales, dolphins, sperm whales, killer whales and porpoises Cetaceans evolved from a species of terrestrial carnivorous ungulate more than 50 million years ago. The order Cetacea is divided into three suborders (one of which is extinct):
- Archaeoceti: quadrupedal terrestrial animals that are predecessors of today's cetaceans (extinct).
- Mysticeti: These are the baleen whales. They are toothless carnivorous animals that take large mouthfuls of water, then filter it through their baleen and scoop up trapped fish with their tongues.
- Odontoceti-This includes dolphins, killer whales, porpoises, and beaked whales. It is a very diverse group, although its main characteristic is that they have teeth. In this group we can find the pink dolphin (Inia geoffrensis), a species of aquatic river mammal.
Aquatic mammals of the order carnivora
In the order carnivora we include seals, sea lions and walruses, although sea otters and polar bears could also be included. This group of animals appeared about 15 million years ago and is believed to be closely related to mustelids and ursids (bears).
Aquatic mammals of the order Sirenia
The last order, sirenia, includes dugongs and manatees These animals have evolved from the tititerians, animals very similar to the elephants that appeared about 66 million years ago. Dugongs inhabit Australia and manatees in Africa and America.
Examples of marine mammals and their names
Now that we know the characteristics of aquatic mammals, let's see some examples depending on the order to which they belong:
Examples of marine mammals of the order Cetacea
As we have seen, within this order they are divided into three suborders. However, as one of them is extinct, we will see examples of aquatic mammals from the remaining two suborders:
Examples of the suborder mysticeti:
- Greenland Whale (Balaena mysticetus)
- Southern Right Whale (Eubalaena australis)
- Glacial Right Whale (Eubalaena glacialis)
- Pacific Right Whale (Eubalaena japonica)
- Fin whale (Balaenoptera physalus)
- Sei or boreal whale (Balaenoptera borealis)
- Bryde's whale (Balaenoptera brydei)
- Tropical whale (Balaenoptera edeni)
- Great blue whale (Balaenoptera musculus)
- Minimal, Minke or Minke whale (Balaenoptera acutorostrata)
- Southern or Antarctic minke whale (Balaenoptera bonaerensis)
- Omura's whale (Balaenoptera omurai)
- Yubarta or humpback whale (Megaptera novaeangliae)
- Grey whale (Eschrichtius robustus)
- Pygmy whale (Caperea marginata)
Examples of the suborder odontoceti:
- Tonina overa (Cephalorhynchus commersonii)
- Heaviside's dolphin (Cephalorhynchus heavisidii)
- Coastal common dolphin (Delphinus capensis)
- Pygmy killer whale (Feresa attenuata)
- Pilot pilot whale (Globicephala melas)
- Risso's dolphin (Grampus griseus)
- Fraser's dolphin (Lagenodelphis hosei)
- Atlantic dolphin (Lagenorhynchus acutus)
- Northern Finless Dolphin (Lissodelphis borealis)
- Orca (Orcinus orca)
- Hong Kong pink dolphin (Sousa chinensis)
- Striped dolphin (Stenella coeruleoalba)
- Bottlenose dolphin (Tursiops truncatus)
- Boto, Amazon river dolphin or pink dolphin (Inia geoffrensis)
- Baiji or Chinese river dolphin (Lipotes vexillifer)
- Silver Dolphin (Pontoporia blainvillei)
- Beluga (Delphinapterus leucas)
- Narwhal (Monodon monoceros)
Examples of marine mammals of the order carnivora
Let's see below species of aquatic mammals belonging to this order:
- Mediterranean monk seal (Monachus monachus)
- Northern Elephant Seal (Mirounga angustirostris)
- Leopard seal (Hydrurga leptonyx)
- Harbor Seal (Phoca vitulina)
- Australian and South African Fur Seal (Arctocephalus pusillus)
- Guadalupe fur seal (Arctophoca philippii townsendi)
- Steller's sea lion (Eumetopias jubatus)
- California sea lion (Zalophus californianus)
- Sea otter (Enhydra lutris)
- Polar bear (Ursus maritimus)
Examples of marine mammals of the order sirenia
Finally, we finish the list of aquatic mammals with examples of the order sirenia:
- Dugong (Dugong dugon)
- Caribbean Manatee (Trichechus manatus)
- Amazon Manatee (Trichechus inunguis)
- African manatee (Trichechus senegalensis)
