What Is A Marine Mammal?
So, what is a mammal then?
To be classified as a mammal an animal must posses all five of these characteristics.
Obviously there are a lot of examples of animals that live on land that meet these five qualifications, including dogs, horses, cats, rats, pigs and people.
But what about dolphins, whales and porpoises? Hair? Yes, very early in life these animals posses hair around their mouths which are usually lost soon after birth. If you look closely at some of these adult animals you can still see the raised follicles were the hair used to be.
All marine mammals were originally land mammals and share common ancestry and characteristics with every other mammal. Over time they became more and more specialized to meet the challenges of life in an aquatic environment. For example, cetaceans, who live their entire lives in the water, have little need for hair. In fact hair can be a problem by acting as a drag to slow them down as they speed through the water. To be more efficient in the water they have lost almost all of their hair. On the other hand, slower swimming marine mammals that still spend a lot of their time on land, such as polar bears and sea otters, still rely heavily on the protection and insulation that their hair or fur provides.
What are the four general types of marine mammals?
Scientists classify all types of animals and plants by their genetic relationships to each other. This process is called taxonomy. As we have already seen, to be classified as a mammal you need to posses all 5 characteristics listed above. All mammals are members of the "class" Mammalia. Within this class are smaller subgroups called "orders". Three of these orders are made up entirely of marine mammals. They are the orders of Cetacea, Pinnipedia, and Sirenia. A fourth order Carnivora contains both marine and land animals.
Cetaceans - whales, dolphins and porpoises
Pinnipeds - seals, sea lions and walruses
Sirenians - dugongs and manatees
Carnivores - sea otters and polar bears
Copyright © 2000-2011 DolphinTrainer.com. All rights reserved.