Introduction

Marine mammals are fascinating creatures. They are mammals, like us, but they are descended from several different groups of terrestrial mammals (including the groups to which elephants, hippos, and bears belong to). Today there are 3 orders of marine mammals, plus a few species that belong to terrestrial mammal orders.

• The order Sirenia is composed of manatees & dugongs.          http://www.worldwildlife.org/gift-center/Images/large-species-photo/large-dugong-photo.jpg
  

• The order Pinnipedia is composed of true (earless) seals, sea lions, and walruses.                                          http://gothamist.com/images/2005_03_seal-thumb.jpg

• The order Cetacea is composed of toothed whales (such as dolphins) and baleen whales (such as blue whales).                                           http://preservingthesecretsoftheocean.wikispaces.com/file/view/ogcGR_lg_bluewhale.jpg/34305887/ogcGR_lg_bluewhale.jpg

• Sea otters & marine otters are marine mammals that belong to a group of terrestrial mammals called mustelids.                                                                                                                               http://wiki-images.enotes.com/thumb/d/d4/Sea_otter_pair2.jpg/200px-Sea_otter_pair2.jpg

• Polar bears are not considered marine mammals by some because they are not fully marine like the rest, and because they only diverged from their terrestrial sister species, Grizzly bears, about 1 million years ago. They are ursids and belong to the order Carnivora (as do mustelids).                                                                                                                              http://a-z-animals.com/images/blog/pol1.jpg

(Horstmann-Dehn, 2012, & Perrin, 2009)

I decided to make this webpage about marine mammals & the physics of how they live in the ocean, not only because I love marine mammals and I'm very interested in them, but also because the sea is an environment that is so different from our own (and from that of the ancestors of all the groups of marine mammals). As such, not only is the ocean interesting in itself, but it also presents many challenges to mammals, producing a plethora of fascinating adaptations. I only wish I had the time to investigate the subject in more depth, and present to you more of the many ways in which these wonderful creatures are adapted to living in the sea.