INTRODUCTION

Few people have the privilege of observing otters, Lutra canadensis, in the wild. However, most people know about the otter's playfulness and energetic lifestyle. Otters frequently play by sliding down banks into the water over and over again. They also engage in games of tag and much tumbling and wrestling with each other.

The otter belongs to the weasel family which includes mink, weasels and skunks. The otter's scientific name is Lutra canadensis. Lutra is the Latin for otter and canadensis means belonging to Canada. The river otter was first identified in Canada. Chippewa Indians call it neeg-keek, and Potawatomi Indians named it ku-tet-tahx. The French Canadians call it loutre. Common names for the otter include northern river otter, Canadian otter, land otter, and fish otter.

DESCRIPTION

The otter is a cylinder-shaped animal. The otter's neck is nearly the same diameter as its body. Its head is broad and flatten with eyes placed near the top which allows the otter to see while swimming. The ears are small and rounded. The whiskers are long and quickly noticed. Its tail is broad at the base, tapering to the tip and is flattened on the underside.

Like other members of the weasel family, the otter has scent glands located near its anus (opening for depositing body wastes). These glands are used for marking home ranges with scent but are not used for defensive purposes like the skunk does.

The otter's feet are webbed. The foot is fur covered except for the pads of the toes and sole. Both front and back feet have five toes with claws that cannot be retracted (pulled back into a protective sheath).

The otter's fur is dense with a waterproof, oily undercoat and an outer coat of long, stiff guard hairs. The otter's pelage (fur) ranges from dark brown to black on the back and sides. The fur is light brown to silver gray on the stomach and around the lips, cheeks, chin, and throat. Otters shed their fur twice a year with little difference between summer and winter pelage.

The otter is 35 to 55 inches long with the tail representing nearly 1/3 of that total length. Its weight ranges from 10 to 30 pounds with females being about 5% lighter than males.

Adaptations for aquatic life. The otter has a thick layer of fat underneath its fur. This fat provides insulation for swimming in cold waters. It also helps the otter survive cold winters. The otter can close its ears and nostrils when diving. Its body is slender with short legs and webbed feet. Its powerful lungs allow it to swim up to 1/4 mile underwater at speeds up to 6 miles per hour before coming up for air.

HABITAT

Otters are found in large bodies of water containing abundant aquatic life and prey. They also occur in large marshes (flooded cattail, grasses, sedges, and reeds) with areas of deep, open water that rarely dries up. Otters quickly disappear from waterways suffering from pollution, perhaps from pesticide runoffs or increased acidity. The areas where lakes and rivers are being developed into camps or home sites frequently suffer a decline in otter population.

FOOD AND FEEDING BEHAVIOR

The otter is an opportunistic feeder (eating whatever food is available) and a carnivore (meat-eater). It mainly eats slow moving fish such as suckers, chubs, bullheads, and catfish. It may eat some faster moving game fish, such as bass or trout.

Snakes, turtles, frogs and small invertebrates (crayfish, insects, mussels, snails, and earthworms) are consumed when available. Rarely, an otter may eat mammals or birds. Wildlife specialists have observed that otters need a wide variety of food. Captive otters fed only fish do not stay healthy.

The otter dives in the water and chases fish, young muskrats, or birds by swimming just underneath them. It may dig in the bottom of the lake or river using its nose and sensitive whiskers to locate mussels. It catches prey in its teeth and then bobs to the water surface to eat. Larger prey is taken to the shore where the otter may play with it similar to the way cats do. Prey is chewed thoroughly and digested so well that few identifiable parts are found in the otter's scats (droppings or feces of animals). After a meal, the otter cleans its whiskers and face by rubbing on grass or snow.

BEHAVIOR

Courting/Breeding. The otter is sexually mature at 2 years of age. Females usually breed in their second year but males seldom breed successfully before their fifth to seventh year. Males normally have to have established home ranges before they have access to a female to breed with.

A female otter that is ready to breed deposits scent at several locations around her home range. Wildlife biologists speculate that the male can detect a different odor in the scent deposit when the female is ready to breed. The male begins following the female and may fight if another male tries to breed with her.

Otter courting includes vocalizations such as whistles, chuckles, and birdlike chirps. The otter pair spends time nuzzling each other. Actual mating takes place in late winter or early spring, just after the female gives birth. Copulation (mating) takes place in the water. The process may take up to 25 minutes with the male holding on to the female's neck.

Birth. Otters experience a delay of 8 to 13 months between mating and birth. This is because the fertilized egg within the female does not immediately begin growing. Eventually the fertilized egg becomes implanted in the uterus wall and begins growing. The actual pregnancy lasts for about 7 weeks beginning sometime between January and May.

Before giving birth, the female lines her den (home) with leaves and other plant material. In Michigan, otters typically give birth from late March through April.

The cubs (young otters) weigh 8 ounces at birth. They are born blind and toothless. Cubs are covered with black fur. Otter cubs develop very slowly. Their eyes remain closed until 5 or 6 weeks. They don't leave the nest until 3 months of age. The male otter may join the family for a short time now. The female begins taking the cubs on foraging expeditions. The female otter teaches the cubs to swim by taking them for ride on her back into the deep water. Then she swims away from them forcing them to swim to shore on their own. Even otters must be taught how to swim! The cubs may remain with the mother until just before she gives birth the next spring.

Dens. Otters take over dens excavated by beavers, muskrats, and woodchucks. Natural cavities in river banks or under rocky ledges may be used as a den. Dens have openings above water for summer use and below the ice line for winter use. The nest chamber is large and is lined with a layer of leaves or grass. Otters also make temporary dens by weaving marsh grasses together. The same dens may be used for several years

Otters select a place away from the den to deposit body wastes. They bury their wastes like cats do.

Home ranges. Wildlife researchers report home ranges varying between 12-30 square miles for a female with young. Male home ranges may be up to 100 square miles in size. The size of any particular otter's home range depends on the availability of water and food. It is speculated that those otters appearing to have exceptionally large home ranges are actually young otters who have not yet established a permanent home range. The otter remains on the home range year-round. If a marsh or shallow lake should freeze over the winter, otters are usually able to locate another open water source within their home range. However, during extremely cold winters, some otters are forced to leave their territory (at least for the winter) to locate open water.

Neither a male nor a female otter has a home range which overlaps that of another otter of the same sex. The male's home range may overlap several female home ranges. He frequently breeds with the females living in his home range.

Scent mounds. Scent mounds, located on rocks, fallen logs, plants or mounds of earth are scattered throughout the home range. The mound is used for scats (excrement) and musk deposits. Scent mounds help prevent direct conflicts between otters by clearly marking boundaries and important locations within the home range. Other well marked features within a home range include feeding areas and good dens.

Locomotion. Three different swimming methods may be used by the otter. An otter swims by paddling with its back limbs like a dog and using its front limbs for turning. Sometimes it holds its head out of the water. The otter can swim underwater for long distances by coming up for air several times during each mile of swimming. Undulating motions similar to the way dolphins swim may be used.

The otter may walk, run or bound when moving on land. During bounding, the body is held in an arched position and the tail is stiff. The front feet are moved simultaneously and the back feet move simultaneously. The tail is used to balance while traveling on land. Otters use sliding for 3 purposes. First, it is a major form of transportation on land. It is easier for the otter to take a few running steps and slide for several feet than to drag its heavy body across ice or snow. Otters slide down lake or river banks to enter the water. Otters also use slides for play. They slide down a bank, climb back out and do it again, and again, and again!

Communication. Otter vocalizations include a shrill chirping, chuckles, screams, grunting noises, and coughs. These are very soft sounds. It may also communicate a warning toward an intruder by using a "threat face display" which involves pulled back ears and an open mouth.

Signs of otter presence. Haul-outs are places where otters routinely climb out of the water. Rolling places are spots near the edge of a lake or stream where the otter rolls to dry off after climbing out of water. These rolling sites may be up to 20 square feet in size. Muddy slides may be identified on the banks of bodies of water. Bedding sites are circular areas of matted leaves or plants where the otter rests. Den openings may be detected by an abundance of tracks. Diggings consist of loose soil and holes where otters probe for food. Look for otter tracks wherever these signs are found.

Social behavior. Male otters are solitary animals except during breeding season. Females stay with their recent cubs but remain solitary at other times. Family groups are frequently seen playing kitten fashion. This play is actually teaching the cubs to find and eat prey. Much rolling and tumbling is involved.

Otters are nocturnal (active at night) or crepuscular (active at dawn or twilight). They spend much of the rest of the time sleeping in their dens.

Defense. Otters are fierce fighters. They have a powerful bite and are able to fight off even large dogs. Adult otters have few natural enemies among the animal kingdom.

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