) UNC Sea Grant 



I 1/7 



nth '■' . 



2 



August 1982 



Nor^^arotina State Library 



Raleigh 



^ n. a 



COAST SWATCH 



Atlantic bottlenosed dolphin and calf 



Mammals of the sea 



Millions of years ago, they emerged 

 from the sea as amphibians and made 

 the land their home. These fish-like 

 creatures who roamed the earth on 

 four legs evolved into mammals, air- 

 breathing and warm-blooded. They 

 bore their young alive and nursed 

 them. Then, over 50 million years ago, 

 some of them returned to the water as 

 mammals and took the rivers, sounds 

 and open ocean for their home. 



Marine mammals underwent many 

 changes to adapt to a watery environ- 



ment. Their front legs became flippers, 

 and their rear legs disappeared with 

 only small traces of bone remaining in 

 the skeletal structure. Bodies became 

 more streamlined, reducing turbulence 

 and resistance when they moved 

 through the water. Blowholes on the 

 top of the head allowed them to 

 breathe while swimming. They came 

 to resemble large fish, but they were 

 true mammals. 



Today there are three groups of 

 marine mammals: cetaceans (whales, 



dolphins and porpoises); pinnepids 

 (seals, sea lions and walruses) and sire- 

 nians (dugongs, sea cows and 

 manatees). Marine mammals range in 

 size from the blue whale (about 90 feet 

 in length) to the harbor porpoise 

 (about five feet long). Some species, 

 such as the manatee and bottlenosed 

 dolphin, live close to shore while most 

 of the big whales live 30 miles offshore 

 or even farther. 



Continued on next page 



