River Otter

Lutra canadensis interior Swenk



 Color photo by George R. Pisani.
Copyright 1999.   All rights reserved.

Description:   The river otter was the largest member of its family found in Kansas. It can be distinguished by: 1) rounded, flattened head with small ears, 2) short, thick neck, 3) long body, 4) short legs, 5) tail modified for swimming, thick and heavily muscled at the base, and tapered to a point, 6) webbed toes, 7) sleek, dark brown dorsal fur which has a heavy, soft, oily underfur overlain by glossy, smooth guard hairs (giving the otter its smooth, sleek appearance), and 8) light brown fur on the underside.

Size:   Adults may attain the following dimensions: total length 978-1346 mm; tail 353-507 mm;; hind foot 110-138 mm; ear 12-24 mm; weight 5-10.4 kilograms. Males are larger than females.

Range and Habitat:   At one time the river otter was distributed along all the major rivers and many permanent streams throughout Kansas. The last specimen known to have been collected in Kansas was taken in 1904 near Manhattan. River otters may still occur in northeastern Kansas along the Missouri River. Although the river otter prefers aquatic situations, it is occasionally seen some distance from major bodies of water, especially during the breeding season.

Reproduction:   The river otter breeds from late December until early April. Several males may follow a female and fight among themselves for the chance to breed. Copulation may occur in water or on land. Implantation of the embryo in the uterus is delayed until the following January, when development is resumed. After a gestation period of 288 to 380 days, one to four (usually two) young are born in March or April. They weigh about 500 grams and are approximately 180 mm long. The young are born with short dark brown or black fur. Their eyes and ears are closed, but their claws are well-developed. Their eyes open approximately 35 days after birth, and they begin to play around the den when they are five to six weeks old. By the time the reach 10 to 12 weeks of age, they leave the den and follow the female. The female teaches the young to swim and hunt food, bringing live prey in to her offspring, releasing it, and teaching them to capture it. Males are reported to help females care for the young after they leave the den., The young disperse at the start of the reproductive season after their birth, usually moving along streams or rivers until they find an unoccupied area. They are capable of breeding when they are two years old, but males do not seem to be successful in obtaining mates until they are nearly five years old.

Habits:   The river otter is primarily active after sundown, but it may also be active during daylight yours. It tends to forage in and along streams and rivers, and often searches the river bottom for buried prey.

  River otter dens are constructed under tree roots, blow-downs, in thickets, and in abandoned burrows. The dens are usually close to some body of water, but may be more than 0.8 kilometers away for a source. Leaves and grass are gathered to make a nest. Several dens are used within an individual range which may extend over 80 to 100 kilometers of river in a year. However, movement is usually restricted to a smaller (five to 16 kilometer) portion of the range. Throughout their home range river otters have "pulling out" spots where they build scent posts by gathering and piling up debris, and marking it weigh feces and urine. A probable purpose of the scent posts is to inform other river otters of their presence, but there is no evidence that defended territories are established.

Food:   The diet of the river otter reflects its aquatic habits. Up to 60 per cent of the diet may be fish, but voles, deer mice, muskrats, birds, bird eggs, frogs, crayfish, insects and worms are also eaten.

Remarks:   Like other members of the family, river otters have anal musk glands which are used if the otter is threatened. In several states where river otter populations have increased, fisherman have complained that they destroy game fish. Studies of these populations showed that river otters destroyed many trash fish and seldom took game species. Additionally, they helped prevent overcrowding and stunting in fish populations.

  River otters may live up to twenty years in captivity, but probably live at most six or seven years in the wild.

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