Otters are any of the species belonging to the taxonomic subfamily Lutrinae. There are 13 different species, which are native on every continent but Antarctica and Australia. Otters are the smallest marine mammal. Also they have fur to keep them warm instead of blubber. Otters have the thickest fur of all animals with at least 250,000 hairs per square inch. Some species of otters have up to 1 million hairs per square inch. An otter's tail can be up to 40% of their body mass. Otters can hold their breath for 4 minutes under water. 
Otter's bodies are designed for swimming.They can be distinguished by have long, slim, torpedo like bodies and relatively short limbs, with webbed paws that are used for swimming. Sea otters are somewhat stockier than other otters with their larger rib cages. Most have sharp claws on their feet but some genus like Aonyx and Amblonyx have no claws. Genus Enhydra (sea otters) are the only genus of otters that do not have a long muscular tail. The tails of river otters and clawless otters are about one-third of total body length. Freshwater otters uses their tail to propel themselves when swimming to high speed, to steer when swimming slowly, and also to help with balance when standing upright on their hind legs.  Adult sizes can range from 0.6 to 1.8 meters (2 to 6 ft) in length and 1 to 45 kilograms (2.2 to 100 lb) in weight.The Oriental small-clawed otter, Amblonyx, is the smallest otter species and the sea otters and the giant otter are the largest species. All otters have a very thick coat of fur which is comprised of soft, dense underhair and coarse guard hair. The two layers of fur trap air between them, which keeps the otter warm in the water, in contrast to seals, which have a layer of blubber to keep them warm instead. Fish-eating otters have sharp teeth to catch the fish,but shellfish-eating otters have more blunt teeth for crushing shells. Sea otters have 32 teeth, mostly post-canine molars. They are designed for crushing and grinding the shells of invertebrates. Sea otters are the only carnivores with just two pairs of incisors in the lower jaw. Their incisors function in scraping the soft parts of mollusks from their shells. All other otters have three pairs of incisors, which are mostly used for grooming.
Life Cycleriver otters and sea otters come to sexual maturity in their second or third year, but most do not successfully reproduce until they are five to seven years old. Fertilization in many otters happens when a male otter approaches the females until it finds one that is receptive. A male then approaches a female and attempts to embrace her with his forelegs or rub and sniff her. She will push him away or the two will roll and frolic. Copulation is preceded by vigorous play like chasing, swimming, diving, twisting, cork-screwing, and lunging. In some species the male bites the female's upper jaw or nose,and in other species the male grasps the female by the scruff of the neck. Copulation takes place in the water, and lasts from 10 to 30 minutes. All clawless and river otters have a gestation period of about two months.North American, smooth, spot-necked, and marine otters have demonstrated delayed implantation for as long as 10 months. When the fertilized egg has divided into a hollow ball of cells one layer thick (blastocyst stage), it stops developing, and floats in the uterus. After several months the blastocyst implants in the uterine wall and continues to develop. Actual embryonic development takes only about two months. Delayed implantation ensures that the pup will be born when environmental conditions are optimal for its survival. It also allows some recovery time for the mother from her last pregnancy.The giant otter's gestation period lasts about 65 to 70 days. Reports on sea otter gestation have ranged from four to nine months, with an average of six months. Freshwater otters give birth on land in there dens, whereas most sea otter births occur in the water. Sea otters only have one baby otter (pup) at a time. In compare to Freshwater otters that usually have litters of one to three young. River and giant otters may have as many as five pups in a litter, and Asian small-clawed otters may have six pups.
Otters live in Europe, Asia, Africa, North America, and South America. Sea otters live in the Pacific coast of North America. Sea otters also are the only otters that are fully aquatic. North American river otters live in the Coastal waters, rivers, and streams of North America. The Giant otter, the South American River Otter, the Neotropical Otter, and the Marine Otter all live in South or Central America. The Old World Otter are spread throughout Eurasia. The Asian Small Clawed Otter and the Hairy Nosed Otter are scattered in different parts of Asia and the Smooth-Coated Otter lives in various places of Asia. The African Clawless Otter and the Spotted-Neck Otter both live in the same area of Africa. Otters are mainly terrestrial and semi-aquatic animal, besides the sea otter which is aquatic.
Otters use the water mostly for food. River Otters eat fish, frogs, crab, crayfish, and other aquatic invertebrates. They also occasionally eat birds, rabbits, and rodents. Giant otters mainly eat crab and fish. Cape clawless and Asian small-clawed otters mainly eat crustaceans, crabs, mollusks, and frogs. A Sea Otter's diet consists of slow moving fish and marine invertebrates. Otters have a high metabolic rate which is important so they can move quickly and generate body heat. River otters eat 15% to 20% of their total body weight each day and Sea otters eat about 25% to 30% of their weight. A large male Sea Otter can eat 25lbs. of food daily. Otters are preyed on by different animals. They are eaten by eagles, wolves, and bobcats on land and at sea sharks, whales,and spifically killer whales.
Endangerment and Restoration
The population of otters has not recovered to the size that it once was before the hunting of their fur. All species of otters are near the brink of endangerment, but only the Marine Otter is endangered.In 1983-1984, 135 river otters were taken with an average selling price of $1,871 for their pelts. Also, in 1750 ,there was about 15,000 sea otters off the California coast before the hunters came for there fur. By the early 1900s there was 50 sea otters off the coast. Otters are still being poached for their fur. Also, the water is being polluted and in oil spills otters' fur get matted and loses its insulation abilities. Some have got hypothermia after they have had oil on their coat. Otters face a limited amount of food due to fishing also they have accidentally been caught in nets and have drowned because they were stuck. Pathogens and parasites from fish have weakened the Otters' immune system and have killed a number of them. In more recent times there has been many different recovery and conservation plans around the country and world for otters. In Washington State their recovery plan has brought about 8.2% increase of Otter population yearly. 
This is a video of a Giant Otter family in the wild.
- Lutrinae classification Animal Diversity Web. Web. 2013
- Otter World Otter World. Web. Accessed February 27,2013
- Facts about Otter Encyclopedia Of Life. Web. February 11,2013 date access.
- otters lutrinae Seapic.Web. December 14,2007 last updated
- Otters Seaworld .Web. February 11,2013 last updated
- Walters, Emily 5 Thing you did not know about OttersSuite 101 .web. date of publication July 12,2012
- Monterey Bay Aquarium foundation. Sea Otters at risk "Monterey Bay Aquarium" web. Accessed February 27,2013