Whereas most mammals are terrestrial or associated with freshwater habitats, about 2% of the world�s mammalian species spend part or all of their time in marine habitats. There are two main groups of marine mammals: the Pinnipeds (seals, sea lions, walrus) and the Cetaceans (whales, dolphins, porpoises). The Pinnipeds are easily recognized as mammals, having nostrils and four limbs and breeding on land (or ice). By contrast, the Cetaceans are surprising mammals, having a single nostril on top of their heads (blowhole), and being unable to move about on land. Yet both Pinnipeds and Cetaceans are indeed mammals, having placentas and live births, suckling their young, being �warm-blooded,� and breathing air with lungs.
Canadian waters are home to about a quarter of the world�s Cetaceans and Pinnipeds: about 35 species of whales, dolphins, and porpoises and a further 11 species of seals, sea lions, and walrus. In addition, we have one species of sea otter. The Eastern Arctic and Western Arctic ocean regions have many fewer species (10 and six species, respectively). However, they contain species occurring nowhere else in Canada � for example, the Atlantic Walrus and the bizarre tusked Narwhal. Due to their highly migratory nature, some of the larger Cetaceans (e.g., Fin Whale, Right Whale, Blue Whale, and Humpback Whale) can be found in Canada only during the summer months. At this time of year, the cool temperate waters off the coasts of British Columbia and the Atlantic provinces provide highly productive feeding grounds rich in zooplankton, krill, and forage fish species.
About two-thirds (69%, 31 species) of Canada�s marine mammal species are considered Secure, but two species have already been extirpated in the Atlantic ocean region (Gray Whale and Atlantic Walrus), and one species (Sea Mink) is Extinct. A further three (7%) species are classified as At Risk nationally, including the Black Right Whale, which is widely considered to be the most Endangered large whale in the world today. Five more marine mammal species are considered Sensitive.
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