Home >> Science & Nature >> Animals & Science

Mammals That Have Hair and Live in the Ocean

Although some physically resemble fish, marine mammals actually evolved from land animals that crept back into the water to escape predation and find food. Aquatic mammals breathe with lungs and must occasionally come to the surface to take in air. They spend much of their lives in or near water, often coming onto land only for breeding. Many have adopted flippers, fins and flattened tails to aid in swimming. Some species have almost entirely lost their body hair in exchange for more efficient swimming, while others possess massive amounts of water-repelling fur to keep them warm in frigid waters. Almost all marine mammals have a thick layer of insulating fat, or blubber, to store excess energy reserves and help the animals float. In the past, hunters exploited populations of marine mammals for their thick furs and blubber.

Cetaceans
- Dolphins use echolocation to find prey underwater.
  
  Order Cetacea comprises two suborders: Mysticeti -- the baleen whales -- and Odontoceti -- the other whales, dolphins and porpoises. Cetaceans possess little body hair, front limbs transformed into flippers, a flat tail, an opening atop the head and a layer of blubber. Many species, including the humpback whale and dolphins, engage in vocal communications. Baleen whales produce a groaning sound that carries through hundreds of kilometers of water. Odontocetes employ echolocation to find the position of objects and organisms in the water by emitting a series of clicking sounds through an organ on the head called a melon; the middle ear picks up the sound waves that bounce off objects in the water. Some whales journey great distances annually to eat or mate.
Dugongs and Manatees
- Sea cows are related to elephants.
  
  Dugongs and manatees -- the sea cows -- belong to order Sirenia, but actually have a close ancestral relationship to elephants. Only four species remain in this order; habitat destruction and relentless hunting of these gentle creatures have decreased their numbers to near extinction. Sirenians can weigh over 1,150 kilograms, possessing massive bones that keep the animals submerged. A streamlined shape, nostrils placed atop the snout and limited hair contribute to the sirenian's underwater existence. All species eat only vegetation.
Pinnipeds
- Seals spend part of their lives on land.
  
  Although pinnipeds -- which include the walruses, seals and sea lions -- stay water-bound most of the time, they do climb onto land to reproduce and shed their fur once a year. Pinnipeds tend to live close to the coastlines of every continent, including Antarctica. True seals lack the external ear flaps of sea lions and fur seals. Sea lions and fur seals have hind flippers they can maneuver independently, whereas true seals must move their hind limbs as a unit. Hair covers most of a pinniped's body and a substantial layer of blubber lies just beneath the skin for insulation.
Polar Bear
- Polar bears have partial webbing on their feet for more efficient swimming.
  
  Zoologists consider polar bears marine mammals, although they do not depend on the water as much as other aquatic mammals. Polar bears inhabit the hostile, cold regions of North America, relying on their considerable hairy outer coverings and underlying fatty layers to keep them warm. Instead of flippers, polar bears have feet with digits partially connected with webbing designed for a semi-aquatic lifestyle. Polar bears prefer seals as their main prey, but sometimes consume walruses and small whales when available. These bears typically live solitary lives and do not remain in one place for long, choosing to travel up to 40 miles a day to locate food sources. Large bodies, long claws and sensitive noses number among the adaptations that make the polar bear a fearsome predator.
Sea Otter
- Sea otters have the densest fur in the animal kingdom.
  
  Sea otters inhabit the coastlines on both sides of the northern Pacific Ocean, spending most of their lives in the water with occasional appearances on land when the water becomes too crowded. These marine mammals have the thickest fur -- a density of up to 100,000 hairs per square centimeter -- of all animals and have no insulating layer of blubber. In the early 20th century, fur traders killed otters for their pricey pelts, almost to the point of extinction. The otter's webbed feet and long tail contribute to its maneuverability underwater at speeds of up to 9 kilometers per hour. Otters eat up to 25 percent of their weight in food daily to maintain their high levels of activity. These creatures exhibit an intelligence not often seen in the animal world, employing tools such as rocks to break open oyster shells.

Animals & Science