Aquatic and semi-aquatic mammals are well adapted to life in water, with physical characteristics such as flippers, webbed feet, paddle-like tails and streamlined bodies. Whales, dolphins, porpoises, manatees and dugongs are fully aquatic; seals, sea lions, walruses, hippopotamuses, platypuses, otters, beavers and otters are semi-aquatic and spend part of their lives on land.
What makes an aquatic mammal an aquatic mammal?
They must meet the characteristics of all mammals plus the last one:
- They breathe air through their lungs
- They are warm-blooded
- Have hair (at some point in life)
- Produce milk to suckle their young
- Live most or all of their lives in or very near the ocean.
Types of aquatic mammals
As we have said before, we have more or less 2 main groups, the aquatic or marine ones and the semi-aquatic ones. Actually, there are 4 types of marine mammals: cetaceans, pinnipeds, sirenians and physipeds.
Cetaceans: Whales, dolphins and porpoises
- Cetaceans are classified into two main groups: baleen whales (mysticete) and toothed whales (odontocete). They spend their lives in the water and have many adaptations related to their fully aquatic lifestyle. There are more than 70 different species of cetaceans.
Pinnipeds: Seals, sea lions and walruses
- Pinnipeds belong to the suborder pinnipedia, which means “with flippers”. These carnivores use flippers to move both on land and in the water. Pinnipeds spend most of their lives swimming and eating in the water and come close to land or ice floes to have their young, rest and molt.
Sirenians: Dudongs and manatees
- Sirenians also spend their entire lives in the water. They are the only group of marine mammals that are totally herbivorous. Sirenians get their name from the sirens, the legendary Greek sea beauties that lured sailors to sea. Some believe that historical sightings of mermaids were actually sirenians.
Physipeds: Sea otters and polar bears
- Marine fissipeds are considered aquatic mammals, but they spend most of their time on land and only part of their time in the water, mainly to hunt for their food.
Which animals are aquatic or marine mammals?
Here we are going to give you a list of the aquatic mammalian animals that we know best to this day, maybe there are still some left to discover, who knows 🙂
There are 128 known species of marine mammals.
Aquatic mammals: Fresh Water
- Amazonian Manatee(Trichechus inunguis)
- West African Manatee(Trichechus senegalensis)
- Gangetic and Indus dolphin, Platangangeca with two subspecies
- Gangetic (or susu) dolphin, Planista gangetica gangetica
- Indus (or Bhulan) dolphin, Platanista gangetinor
- Amazon dolphin (or Boto), Inia geensis
- Chinese river dolphin (or Baiji), Lipotes velifer (extinct since December 2006)
- La Plata (or Franciscana) dolphin, ntoporia blailei
- European otter (Lutra lutra)
- Sumatran otter (Lutra atrana)
- Spotted collared otter (Hydrictis maculicollis)
- Smooth-necked otter (Lutrogale perspicillata)
- Canada otter (Lontra canadensis)
- Common red-eared whiptail (Lontra provocax)
- Giant otter (Lontra longicaudis)
- Giant otter (Pteronura brasiliensis)
- Clawless otter (Aonyx capensis)
- Asian small clawed otter (Aonyx cinerea)
- Nerpa(Pusa sibirica)
- Lake Ladoga seal(Pusa hispida ladogensis)
- Lake Saimaa seal (Pusa hispida saimensis)
- Capybara(Hydrochoerus hydrochaeris)
- American beaver(Castor canadensis)
- European beaver(Castor fiber)
- Muskrat (Ondatra zibethicus)
- Coypu(Myocastor coypus)
- Water rat (Arvicola amphibius)
- Platypus (Ornithorhynchus anatinus)
- Hippopotamus(Hippopotamus amphibius)
- Pygmy hippopotamus(Choeropsis liberiensis)
- Giant water shrew(Potamogale velox)
- Musky desman(Desmana moschata)
- Possums
Marine mammals: Saltwater
- Bowhead whale(Balaena mysticetus)
- Southern right whale (Eubalaena australis)
- Glacial right whale (Eubalaena glacialis)
- Pacific right whale (Eubalaena japonica)
- Fin whale (Balaenoptera physalus)
- Sei whale (Balaenoptera borealis)
- Bryde’s whale (Balaenoptera brydei)
- Bryde’s whale (Balaenoptera edeni)
- Bryde’s or blue whale (Balaenoptera musculus)
- Minke or minke whale (Balaenoptera acutorostrata)
- Antarctic minke whale (Balaenoptera bonaerensis)
- Omura’s minke whale (Balaenoptera omurai)
- Humpback whale (Megaptera novaeangliae)
- Gray whale(Eschrichtius robustus)
- Pygmy whale(Caperea marginata)
- Commerson’s dolphin (Cephalorhynchus commersonii)
- Heaviside’s dolphin (Cephalorhynchus heavisidii)
- Coastal common dolphin (Delphinus capensis)
- Pygmy killer whale (Feresa attenuata)
- Pilot whale(Globicephala melas)
- Risso’s dolphin (Grampus griseus)
- Fraser’s dolphin (Lagenodelphis hosei)
- Atlantic dolphin (Lagenorhynchus acutus)
- Northern finless dolphin (Lissodelphis borealis)
- Common killer whale (Orcinus orca)
- Hong Kong pink dolphin (Sousa chinensis)
- Striped dolphin (Stenella coeruleoalba)
- Bottlenose dolphin (Tursiops truncatus)
- Beluga whale(Delphinapterus leucas)
- Narwhal(Monodon monoceros)
- Mediterranean monk seal(Monachus monachus)
- Northern elephant seal (Mirounga angustirostris)
- Leopard seal(Hydrurga leptonyx)
- Common or harbor seal(Phoca vitulina)
- Australian and South African fur seal (Arctocephalus pusillus)
- Guadalupe fur seal (Arctophoca philippii townsendi)
- Steller sea lion (Eumetopias jubatus)
- California sea lion(Zalophus californianus)
- Sea otter (Enhydra lutris)
- Polar bear(Ursus maritimus)
Where do marine mammals come from?
Marine mammals play a variety of ecological roles, including herbivores (manatees), filter feeders (baleen whales) and top predators (killer whales). Mammals evolved on land about 160 million years ago. Each taxonomic group of marine mammals evolved from a different group of land mammals, whose ancestors ventured separately into the ocean environment. Despite these different origins, many marine mammals evolved similar traits; streamlined bodies, limbs and paddle-shaped tails, through convergent evolution.
