Playful and proud, river otters are born to have
fun. At least, it appears that river otters are
having fun, because of their playful antics with
each other, as well as their facial and body expressions.
By any measure, otters are extremely curious
and intelligent mammals.
Adult river otters reach a length of about 127 centimeters, including their tails, which are nearly one third of that length. Adults weigh between five and fourteen kilograms. Females are slightly smaller than males. River otters have a dense, short fur with great water resistance. Air is trapped beneath their dense furry coats and acts as insulation against the cold water, where these mostly aquatic mammals feed. Otters roll and rub themselves on sand, rocks, old logs, and even snow in their coat grooming activities. These carnivorous mammals mostly feed on fish. Crayfish also serve as diet items when abundant. Researchers have found that river otters feed directly on fish proportionally to their availability and inversely to the fish's swimming ability. Shelters that have been abandoned by other animals are frequently used by river otters, such as old beaver dens or riverbank excavations. On occasion, river otters use rock piles and log jams as dens. Some investigators have discovered nests along river and stream banks which river otters had constructed of aquatic vegetation. Mating activity usually occurs in the water, although there are reports of mating on land. The breeding season is usually late winter to spring. Litter size is between one and six cubs. The newborn otters have full pelage, but their eyes are not open and they have no erupted teeth. Females wean their young at about three months of age. Several predators, including bobcats, foxes, and alligators, have been observed dining on river otters. Humans also have made their impact on otter populations in at least three ways: habitat destruction, water pollution, and overtrapping.
Another interesting otter is the sea otter. These seafaring mammals are confined to the northern Pacific Ocean. Being the largest in the family Mustelidae, sea otters weigh between twentyseven and thirty-eight kilograms and attain a length of about 148 centimeters. Unlike seals and whales, which have a fat layer (blubber) for insulation, sea otters rely on air trapped beneath their densely packed pelage. Some researchers have estimated the number of hairs in a sea otter's coat to be 800 million. Sea otters, just as their freshwater cousins, have delayed embryo implantation. Females usually produce one pup in a litter. The pup is unable toswimor dive until it is two to three weeks old. Food preferences of sea otters include abalones, sea urchins, clams, and crabs. It is a common practice of sea otters to eat while floating on their backs. Furthermore, sea otters use rocks to open the shells of their diet items, making them a member of a small group of animal tool users. Unlike other members of the Mustelidae, sea otters lack functioning anal scent glands. Also, unlike most carnivores, sea otter teeth are adapted to crushing their prey, rather than tearing.
Genus and species: Lutra canadensis (North American river otter), L. lutra (European river otter), L. felina (marine otter), L. provocax (southern river otter), L. longicaudis (neotropical river otter), L. umatrana (hairy nosed otter); Hydrictis maculicollis (spot-necked otter); Lutrogale perspicillata (Indian smoothed-coated otter); Aonyx cinera (oriental short-clawed otter), A. capensis (Cape clawless otter); Pteronura brasiliensis (giant otter); Enhyda lutris (sea otter)
Geographical location: Until the eighteenth century, North American river otters were found in all major water courses in the United States and Canada; presently, river otters are scattered in several river systems across the United States and Canada, and many river otters have been reintroduced into river systems where they once flourished
Habitat: Exclusively aquatic, adaptable to many nonpolluted aquatic environments
Gestational period: 288 to 375 days, with delayed implantation
Life span: Ten years, with a maximum of twenty-three years Special anatomy: Webbed feet
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