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The River Otter is a Beloved Oregon Coast Critter
Oregon Coast Notes - News

River OtterThe North American River Otter (Lontra canadensis), also known as the Northern River Otter or the Common Otter, is a semi-aquatic mammal endemic to the North American continent, found in and along its waterways and coasts.

The North American river otter is about 21 to 32 inches long with a 12- to 20-inch tail. It can weigh from 10 to 30 pounds. They have short, dense brown fur with a waterproof undercoat. A layer of fat insulates the body. Its body is torpedo-shaped, which is very useful for swimming. Its ears and nostrils close when submerged. Its feet are webbed and suited for swimming. A river otter can swim up to 7 mph and can remain underwater for 6 to 8 minutes.

Behavior

Active yearlong, river otters are active during the day (diurnal). However, with human disturbance, their behavior may become crepuscular (active during dawn and dusk) or nocturnal. They are usually found no more than a few hundred meters from the water. They often take over the former dens of beaver or muskrats, with an entrance below the waterline and above for air exchange.

RiverOtter1North American river otters nest in burrows and cavities in banks, rocks, trees, stumps, in hollow logs, in deserted beaver burrows, in thickets, or on platforms made of wetland plants. Nests lined with dry vegetation, and occur within 0.8 km (0.5 mi) of water.

Social structure

The North American river otter is more social than most mustelids. In all habitats, the basic river otter social group is the family, consisting of an adult female and her progeny. Adult males also commonly establish enduring social groupings that have been documented to comprise as many as 17 individuals. In coastal areas, males may remain gregarious even during the estrous period of females.

Family groups may include helpers, which can be made up of unrelated adults, yearlings, or juveniles. Male otters disperse from such family group more often than female otters. However, when females leave, they tend to move much further away (60-90 km) than males (up to 30km) who tend to move shorter distances. Males can leave up to 16–30 km while female otters can have distances of 60–90 km away from the group. Male river otters seem to be non-territorial and newly dispersing males may join established male groups.

On occasion, groups of unrelated juveniles are observed. River otters that live in groups hunt and travel together, use the same dens, resting sites, and latrines, and perform grooming.

In freshwater systems, groups occur most often in autumn and during early winter. From mid-winter through the breeding season, adult females move and den alone. River otters are not territorial, but individual otters of different groups portray mutual avoidance. Home ranges of males are larger than those of females, and both sexes exhibit intra- and intersexual overlap of their domains.

Communication

RiverOtter3Communication among North American river otters is accomplished mainly by olfactory and auditory signals. Scent marking is imperative for intergroup communication. The river otter scent-marks with feces, urine, and possibly anal sac secretions. Musk from the scent glands may also be secreted when otters are frightened or angry..

The river otters can produce a snarling growl or hissing bark when bothered and a shrill whistle when in pain. When at play or traveling, they sometimes give off a low purring grunt. The alarm call, given by an otter when shocked or distressed by potential danger, is an explosive snort, made by expelling air through the nostrils. River otters also may use a birdlike chirp for communication over longer distances, but the most common sound heard among a group of otters is low-frequency chuckling.

Gestation

They have a gestation of 60 to 63 days. Pups are born in the spring in litters of 2 to 4. After 8 months, they leave the mother. In captivity their lifespan is about 18 years with the record being 21 years.

Diet

In the wild, river otters eat small mammals, small fish, frogs, insects, small birds, eggs and mollusks. They have also been know to occasionally eat fruits, such as blueberries At the Oregon Zoo, they are fed carnivore diet, fish with vitamins, omnivore biscuits and chicken necks.

Prey are captured with a quick lunge from ambush or, more rarely, after a sustained chase. River otters can remain underwater for nearly 4 minutes, swim at speeds approaching 11 km/h, dive to depths nearing 20 meters, and travel up to 400 meters while underwater. Several river otters may even cooperate while fishing. Small fish are eaten at the surface but larger ones are taken to the shore to be consumed. Live fish are typically eaten from the head.

Habitat

RiverOtter2Suitable habitat consists of riparian and other wetland vegetation associated with a large, permanent water source. Cover provided by thickets, tall wetland plants, hollow logs, stumps, snags, and burrows and other cavities. River otters are found in marshes, streams and river mouths in Canada and the United States.

River otters are non-migratory, but may travel long distances along watercourses, or even over land in search of a mate, or a new living area.
Home ranges may extend an average of 15 mi, or more, along rivers and streams. Travel distance is highly variable, and related to food supply, suitable habitat, and inherent wandering.

Status

Because of habitat destruction and water pollution, river otters are listed as rare under CITES App II (except in the Northwest). Good populations exist in suitable habitat in the northeast and southeast and they are protected and regulated by the Oregon Department of Fish and Wildlife.

Other

Few predators other than humans. Generally do not affect population numbers of game fish; may improve sport fishing because they eat mostly slower, nongame fish

The North American otter is one of the few members of the weasel family specially adapted to water habitats.

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