how many sea mammals are there?

That's a really good question.  You do ask some good ones.  I cannot give you a specific answer so I am going to have a look for you and try and get you a full answer over the next few days.

However here is something to  be going on with, there are Dolphins, whales, and porpoises.  Seals, walruses, and dugongs.  Some people might include polar bears.  I will have a look and try to find a few numbers of species, for the types of animals that I have mentioned.  Another expert might be able to help while you are waiting for more from me........

As Neil implies, it kind of depends on your definition. Biologists generally use two different classifications for animals that live in water - aquatic and semi-aquatic. Both are informal definitions and do not relate to how the species are related, just their lifestyle.

Aquatic animals live inthe water and never leave such as whales and dougons, but semi-aquatic animals can also live on land like otters and polar bears. Of course the semi-aquatic animals can vary in how much they swim - sea otters rarely leave the water but Asian short-clawed otters don't swim much at all.

As for the list and number of species, I'll leave that for Neil!

Hi Rudi,

I may have taken on a much bigger task than anticipated here.  However, here goes....Mammals that a strictly aquatic, and never leave the water are very numerous, aswell as many that live in the sea  to hunt but come out onto land to sleep , or breed, or give birth.  I was very surprised by how many species we know of.  There are 5 known species of sea cow (the Sirenia, the dugongs and manatees); 15 species of Seal; 14 species of sea-lion/fur seal; 1 species of walrus; 47 species of dolphin;  35 species of whales.  The whole list that I have is below, and you can find out much more information from Wikipedia.  I got most if the information and the list from there myself.  What is very sad is that the list could be much longer, but there are a lot of extinct species included in the lists that Wikipedia gives.  Some species might have become extinct naturally, but many have been hunted by people.  Thank you for a good question.  I have learnt something from this, because I had no idea that we had so many marine, sea, mammals.
Keep asking good questions!

First: There are 35 true whale species
Whales- Baleen whales (no teeth they filter water for shrimp-like krill)

    * Bowhead Whale, Balaena mysticetus
    * Atlantic Northern Right Whale, Eubalaena glacialis
    * Pacific Northern Right Whale, Eubalaena japonica
    * Southern Right Whale, Eubalaena australis
    * Fin Whale, Balaenoptera physalus
    * Sei Whale, Balaenoptera borealis
    * Bryde's Whale, Balaenoptera brydei
    * Pygmy Bryde's Whale, (Eden's Whale) Balaenoptera edeni
    * Blue Whale, Balaenoptera musculus
    * Northern Minke Whale, Balaenoptera acutorostrata
    * Southern Minke Whale, (Antarctic Minke Whale) Balaenoptera bonaerensis
    * Balaenoptera omurai, discovery announced November 2003. No common name yet in usage
    * Humpback Whale, Megaptera novaeangliae
    * Gray Whale, Eschrichtius robustus
    * Pygmy Right Whale, Caperea marginata

Toothed Whales
* Sperm Whale, Physeter macrocephalus
    * Dwarf Sperm Whale, Kogia sima
    * Pygmy Sperm Whale, Kogia breviceps
    * Cuvier's Beaked Whale, Ziphius cavirostris
    * Arnoux's Beaked Whale, Berardius arnuxii
    * Baird's Beaked Whale (North Pacific Bottlenose Whale), Berardius bairdii
    * Shepherd's Beaked Whale (Tasman Beaked Whale), Tasmacetus shepherdi
    * Longman's Beaked Whale (Indo-Pacific Beaked Whale), Indopacetus pacificus
    * Northern Bottlenose Whale, Hyperoodon ampullatus
    * Southern Bottlenose Whale, Hyperoodon planifrons
    * Hector's Beaked Whale, Mesoplodon hectori
    * True's Beaked Whale, Mesoplodon mirus
    * Gervais' Beaked Whale, Mesoplodon europaeus
    * Sowerby's Beaked Whale, Mesoplodon bidens
    * Gray's Beaked Whale, Mesoplodon grayi
    * Pygmy Beaked Whale, Mesoplodon peruvianus
    * Andrews' Beaked Whale, Mesoplodon bowdoini
    * Bahamonde's Beaked Whale, Mesoplodon bahamondi
    * Hubbs' Beaked Whale, Mesoplodon carlhubbsi
    * Ginkgo-toothed Beaked Whale, Mesoplodon ginkgodens
    * Stejneger's Beaked Whale, Mesoplodon stejnegeri
    * Layard's Beaked Whale, Mesoplodon layardii
    * Blainville's Beaked Whale, Mesoplodon densirostris
    * Perrin's Beaked Whale, Mesoplodon perrini
    * Narwhal, Monodon monoceros
    * Beluga, Delphinapterus leucas

second: Dolphins
41 species plus the 6 members of the dolphin family (Delphinidae), that are called whales, so 47 species altogether.
* Melon-headed Whale, Peponocephala electra
    * Killer Whale, Orcinus orca
    * Pygmy Killer Whale, Feresa attenuata
      Wolphin Kawili'Kai at the Sea Life Park in Hawaii.
      Wolphin Kawili'Kai at the Sea Life Park in Hawaii.
    * False Killer Whale, Psudorca crassidens
    * Long-finned Pilot Whale, Globicephala melas
    * Short-finned Pilot Whale, Globicephala macrorhynchus

Third the Pinnipeds: Walruses, seals, sealions and fur seals
1 species of walrus

Family Odobenidae

    * Walrus, Odobenus rosmarus

14 species of sealion and fur seal
Family Otariidae

          o Northern Fur Seal, Callorhinus ursinus
          o Antarctic Fur Seal, Arctocephalus gazella
          o Guadalupe Fur Seal, Arctocephalus townsendi
          o Juan Fernandez Fur Seal, Arctocephalus philippii
          o Galapagos Fur Seal, Arctocephalus galapagoensis
          o Cape Fur Seal, Arctocephalus pusillus
          o New Zealand Fur Seal or Southern Fur Seal, Arctocephalus forsteri
          o Subantarctic Fur Seal, Arctocephalus tropicalis
          o South American Fur Seal, Arctocephalus australis
          o Steller's Sea Lion, Eumetopias jubatus
          o California Sea Lion, Zalophus californianus
o South American Sea Lion, Otaria flavescens
          o Australian Sea Lion, Neophoca cinerea
          o New Zealand Sea Lion, Phocarctos hookeri

15 species of seal
# Family Phocidae

    * Subfamily Monachinae
          o Tribe Monachini
+ Hawaiian Monk Seal, Monachus schauinslandi
                + Mediterranean Monk Seal, Monachus monachus
                + Caribbean Monk Seal, Monachus tropicalis (probably extinct around 1950)
          o Tribe Miroungini
                + Northern Elephant Seal, Mirounga angustirostris
                + Southern Elephant Seal, Mirounga leonina
          o Tribe Lobodontini
+ Ross Seal, Ommatophoca rossi
                + Crabeater Seal, Lobodon carcinophagus
                + Leopard Seal, Hydrurga leptonyx
                + Weddell Seal, Leptonychotes weddellii
* Subfamily Phocinae
o Bearded Seal, Erignathus barbatus
          o Hooded Seal, Cystophora cristata
          o Tribe Phocini
                + Common Seal or Harbor Seal, Phoca vitulina
                + Spotted Seal or Larga Seal, Phoca largha
                + Ringed Seal, Pusa hispida (formerly Phoca hispida)
                + Nerpa or Baikal Seal, Pusa sibirica (formerly Phoca sibirica)
                + Caspian Seal, Pusa caspica (formerly Phoca caspica)
                + Harp Seal, Pagophilus groenlandica (formerly Phoca groenlandicus)
                + Ribbon Seal, Histriophoca fasciata (formerly Phoca fasciata)
       + Grey Seal, Halichoerus grypus

There are also 5 species of Sirenia, the Dugongs or Manatees

Last edited by Neil Gostling (8th Dec 2007 12:19:24)

Just to be really awkward the Baikal seal lives in a lake, not the sea, so strictly is not a sea mammal, though of course it is semi-aquatic.

Oh, and Darren will hopefully weigh in on this, but apparently there is every chance that there are plenty more large sea mammals yet to be scientifically described; several of those that we do know about are very new to science, and after all down below the surface of the sea is an excellent place for big animals to hide from inquisitive humans.

Yes that's true, we have found two or three new dolphins in the last few years.

And thank's for the grammar / dictionary correction Mike. Good to see peer review at work on AAB ;-)


If we were to spend our time correcting your grasp (and I use the term loosely!) of semiotics, there'd be no time for answering other questions. ;>)

Cheers Dave.....

While I am sure there are more sea mammals to be discovered, I would say it is unlikely there are all that many. Mammals have the distinct disadvantage that they are all air-breathers, so they have to spend a fair bit of time at the surface, making them more likely to be found as they can't hide in the depths for longer than they can hold their breath.

It is much more likely that there are unknown large fish and molluscs as they never have to come up for air (and jelly fish! we can't forget the giant jellyfish as much as the Japanese would love to, referencing for those that haven't heard the giant jellyfish invasion of the Sea of Japan).