Wednesday, 12 October 2011
OtterOtters are inquisitive, playful and intelligent, often appearing to take childlike enjoyment in sliding around on muddy banks or in snow. They are semi-aquatic mammals and live in holts around water edges. They are fast, agile swimmers. Bubbles of air trapped in their fur give them a silvery appearance underwater.
Common names: Common otter, Eurasian otter, Eurasian river otter, European otter, Old world otter
THE RIVER OTTER (Lutra canadensis)
The river otter, found in the United States and Canadian waterways, is a sub-species of the Otter (Lutrinae), which belongs to the martens (Mustelidae) family. The river otter is called Nutria del Canada or Nutria Norteamerica (Spanish), Lontre du Canada (French), Kanada-Otter or Nordamerikanischer Fischoter (German) and Lontre Canadese (Italian).
River otters have existed for a long time. Their fossils date back to the Pleistocene period. Archeological remains have been uncovered from 200 BC to the mid-1400s.
Otters are expert swimmers and divers, swimming at an average speed of seven miles per hour and staying underwater for up to 2 minutes. Unlike muskrats or beavers, the otter barely makes a ripple when swimming or splash when diving. Their specially built ears and nose have a valve-like skin that closes and keeps the otter watertight underwater.
The otters nose is diamond shaped, with two nostrils at the bottom of the nose. Otters communicate with their noses, mainly by smelling marked territories. When they do talk, it is with chirps, chuckles, grunts, whistles and screams.
River otters are most active from early evening through early morning. They are active all year, even in the cold Alaskan winters. Otters play more than most wild animals -- wrestling, chasing other otters, tossing and diving for rocks and clamshells, toying with live prey and occasionally, sliding.
Otters' webbed and clawed feet are good for running and swimming. River otters can run up to 15-l8 mph. They run and slide -- gliding as much as 25 feet on ice and ending with a tumble into a snowdrift or splash into the water.
River otters are three to four feet long and weigh 15 to 25 pounds. They live up to 25 years in captivity and about 15 years in the wild. Their colorful coats range from nearly black to reddish or grayish brown on their backs. The belly is silvery or grayish brown. The throat and cheeks are silvery to yellowish gray. The velvety thick fur is the most durable North American fur and has been in demand ever since Europeans came to this continent.
Even today, people hunt otters for their fur. Bummer! In recent years, more than 50,000 otters have been taken in North America. The otter harvest in Louisiana sometimes exceeds 10,000 animals, higher than in any other state.
Otters have few natural enemies, especially in water. On land, young otters are vulnerable to a variety of predators such as the fox, wolf and raptors. Most otter mortality is related to humans. Legal otter harvests remove animals above what the habitat will support. Otters are fairly easily trapped and accidental trapping, primarily in beaver traps, is a problem.
Other harmful human actions include habitat destruction and adding pesticides and pollutants -- mercury, DDT, dieldrin and polychlorinated biphenyl -- into the food chain. Since otters are at the top of the food chain (they eat animals that eat other animals that eat other animals . . .), these nasty chemicals are concentrated by the time they reach the otters.
River otter have disappeared or are rare through most of their range. River otters do well in Alaska and most of Canada, in the Pacific Northwest, the Great Lakes and most states along the Atlantic Coast and Gulf of Mexico. The good news is that Nebraska, New York and Indiana are re-introducing otters.
Otter populations are extremely sensitive to changes in habitat. They have disappeared from nine states and one Canadian province. The primary cause of decline was habitat pollution and destruction. Hunting, currently legal in some US states and all Canadian provinces, also reduces otter numbers.
River otters use a variety of habitats. They frequent lakes and ponds, but usually live in marshes and along wooded rivers and streams. Otters live in dens, usually borrowed from beavers, muskrats or woodchucks.
Brush piles and root areas under large trees are used as temporary homes. Beavers are important to otters, for the dens they build, and because beaver ponds make ideal otter habitat.
Dens have openings above water in summer, but in winter these are closed and the only entrance is below water. The entrance opens up to a large nest chamber, which may have a bare floor or a slight accumulation of leaves or grass.
River otters require a large amount of space. This home range varies considerably depending on age, gender and food availability. Throughout a year, an otter may occupy 50 or more miles of a stream. Otters may occupy only a few miles of stream, but often move from one area to another.
Otters are carnivores (meat eaters). They eat crustaceans (animals with shells), amphibians, reptiles, birds and insects, but mostly fish. They use their keen sense of touch to find and catch their underwater target. Their sensitive facial whiskers easily detect moving prey. This is especially useful in the murky water created by the otter searching for victims on muddy lake and stream bottoms.
Otters typically hunt by diving and chasing fish, or by digging in the bottom of ponds and streams. Although otters are expert divers, hunting is not always successful. One study found that the success rate of finding food on a dive was less than 20%.
Otters catch prey with their mouths and use their forelimbs to hold the prey. They eat their prey head first and discard the fish fins. After eating, they clean their face and whiskers by rubbing them on grass or snow.
River otters reach sexual maturity when they are two years or older. They breed in March-April and birth in late winter/early spring, about a year later. Litter size varies from one to six, but litters of two or three are most common.
Young otters, called kits, are helpless at birth. Their eyes do not open until they are at least three weeks old. The moms are devoted parents, teaching their children to swim. Moms even catch and release prey to improve the young otters' foraging skills. Otter dads rarely help raise their young.
Baby otters grow quickly, exploring outside the den when they are about two months old. Young otters can care for themselves in about five or six months, but the family usually stays together for a few months longer, often until the birth of a new litter. The young otters leave home when they are about 12 to 13 months of age.