Otter


Geographic Range

The North American River Otter is problably the most numerous otter species. They exhibit delayed implantation with breeding in March-April and birth in late winter/early spring. Fossils of North American River Otters have dated back to the Pleistocene period and archeological remains have been uncovered from 200 B.C. to the mid-1400s.
North American River Otters once lived throughout North America. Native Americans hunted otters largely for their dense fur which allowed them to keep warm. When European settlers arrived and started developing the land (cutting down forests) and using farm pesticides and fertilizers, the otter habitat became threatening. By the early 1980s, eleven states reported no otter population and thirteen other states reported scarce numbers. As a result, numerous reintroduction programs were established to repopulate many of these areas. By late 1990s, many of these programs had successes with a dramatic improvement in returning otters to their original range.

Habitat

North American river otters are found anywhere there is a permanent food supply and easy access to water. They can live in freshwater and coastal marine habitats, including rivers, lakes, marshes, swamps, and estuaries. River otters can tolerate a variety of environments, including cold and warmer latitudes and high elevations. North American river otters seem to be sensitive to pollution and disappear from areas with polluted waters.

North American river otters build dens in the burrows of other mammals, in natural hollows, such as under a log, or in river banks. Dens have underwater entrances and a tunnel leading to a nest chamber that is lined with leaves, grass, moss, bark, and hair.

Physical Description
Mass
5 to 14 kg
(11 to 30.8 lbs)

Length
889 to 1300 mm
(35 to 51.18 in)

North American river otters are semi-aquatic mammals, with long, streamlined bodies, thick tapered tails, and short legs. They have wide, rounded heads, small ears, and nostrils that can be closed underwater. The vibrissae are long and thick, reflecting their importance in sensory perception. The fur is dark brown to almost black above and a lighter color ventrally. The throat and cheeks are usually a golden brown. The fur is dense and soft, effectively insulating these animals in water. The feet have claws and are completely webbed. Body length ranges from 889 to 1300 mm and tail length from 300 to 507 mm. Weight ranges from 5 to 14 kg. Males average larger than females in all measurements.

Reproduction

Breeding interval: Breeding occurs once yearly.

Breeding season: Mating occurs in late winter and early spring.

Number of offspring: 1 to 6; avg. 2-3

Gestation period: 2 months (average)

Time to weaning: 3 months (average)

Time to independence: 6 to 12 months

Age at sexual or reproductive maturity (female): 2 to 3 years

Age at sexual or reproductive maturity (male): 5 to 7 years

Males and females do not associate except during the mating season. Males often breed with several females, probably those whose home ranges overlap with their own.

Males and females come together to breed in late winter or early spring. Gestation lasts two months, but the young may be born up to a year after mating because these otters employ delayed implantation of the fertilized egg in the uterus. Births occur from November to May, with a peak in March and April. Females give birth to from 1 to 6 young per litter, with an average of 2 to 3, in a den near the water. They are born with fur, but are otherwise helpless. They open their eyes at one month of age and are weaned at about 3 months old. They begin to leave their natal range at from 6 months to a year old. Sexual maturity is reached at 2 to 3 years of age.

Females give birth to, nurse, and care for their young in a den near the water. The young are weaned at about 3 months old and begin to leave their mother at 6 months old.

Lifespan/Longevity

North American river otters can live up to 21 years in captivity. They normally live about 8 to 9 years in the wild.

Behavior

Lontra canadensis individuals are solitary, except for females with their young. They are known as playful animals, exhibiting behaviors such as mud/snow sliding, burrowing through the snow, and waterplay. Many "play" activities actually serve a purpose. Some are used to strengthen social bonds, to practice hunting techniques, and to scent mark. North American river otters get their boundless energy from their very high metabolism, which also requires them to eat a great deal during the day.

They are excellent swimmers and divers, able to stay underwater for up to 8 minutes. They are also fast on land, capable of running at up to 29 km/hr. These otters normally hunt at night, but can be seen at all times of day.

Home Range

River otters have large home ranges, between 2-78km of waterway, and are constantly on the move within this range. Home range sizes vary considerably and seem to depend on the richness of food resources and habitat quality. Despite these large ranges, river otters are only slightly territorial and generally practice mutual avoidance.

Communication and Perception

North American river otters communicate in a variety of ways. They vocalize with whistles, growls, chuckles, and screams. They also scent mark using paired scent glands near the base of their tails or by urinating/defecating on vegetation within their home range. These glands produce a very strong, musky odor. They also use touch and communicate through posture and other body signals.

North American river otters perceive their environment through vision, touch, smell, and hearing. Their large and abundant whiskers are very sensitive and are important in tactile sensation. These whiskers are used extensively in hunting, as smell, vision, and hearing are diminished in the water.

Food Habits

North American river otters eat mainly aquatic organisms such as amphibians, fish, turtles, crayfish, crabs, and other invertebrates. Birds, their eggs, and small terrestrial mammals are also eaten on occasion. They sometimes eat aquatic plants.

Prey is captured with the mouth, and mainly slow, non-game fish species are taken, e.g., suckers. The otter's long whiskers are used to detect organisms in the substrate and the dark water. Prey is eaten immediately after capture, usually in the water, although larger prey is eaten on land.

Predation

North American river otters are sometimes taken by bobcats, coyotes, birds of prey,  and other large predators. They mainly escape predation through their agility in the water and on land, their vigilance, and their ability to fiercely defend themselves and their young.