Field Guide/Mammals/River Otter

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Lontra canadensis (North American River Otter)
Family: Mustelidae
Size: Total Length: 35-51.2 inches (889-1300mm)

Tail Length: about 1/3 of total length [1] Height: about 7.8 inches (200mm) when on all fours

Weight: 11-31 pounds (5-14kg)
Description: River otters have a long, slender body with a small head that is wider than tall. They have webbed feet on stump muscular limbs. Their fur is dark brown however appears black when wet. Occasionally they have a cream colored kerchief or belly.
Similar Species: River otters function a lot like sea otters, but sea otters do not come on land and are slightly larger in stature. Sea otters are diurnal, and river otters tend to be nocturnal.

Range: Most major waterways in North America, although sensitive to pollution. The North American River Otter can be found in all major rivers in Minnesota.
Habitat: River otters reside in woods near permanent freshwater rivers or lakes with fish. They stick to a range of 2-78 km from waterways, which they roam for food and mark as their territory.
Diet: One river otter will consume 1-1.5kg fish every day, so otters are mostly carnivorous .[1] River otters tend to eat the “slower fish” that are smaller and not fished commercially. River otters also eat crayfish, crabs, small mammals, birds, some aquatic plants.[2]
Activity: River otters usually hunt at night; they are mostly nocturnal. Otters enjoy sliding on riverbanks and in snow piles, and will swim up to 29 kilometers/hour.[3]

Reproduction: Mating season is in late winter and early spring. They have a 2 month gestation period, although pups may be born up to a year later due to delayed implantation of egg in uterus. Peak births occur in March and April, and litters average 2-3 pups. Pups are weaned after 12 weeks, although mothers will provde food for young for the first three years.[2]
Lifespan: Average 8-9 years wild

Notes: River otters enjoy “trash fish,” the small, slow-swimming kind unsuitable for fishing. Otters are hunted regularly for pelts. They pinch their nostrils shut while underwater, and can stay under for 8 minutes.
North American River Otter


  1. a b Melquist, W.E.; Polechla, P.J.J.; Toweill, D. (2003), G.A. Feldhammer; B.C. Thompson; J.A.Chapman, eds., "River Otter (Lontra canadensis)", Wild Animals of the North America: Biology, Management, and Conservation (Baltimore, MD: Johns Hopkins University Press): 708–734 
  2. a b Larivière, S.; Walton, L. R. (1998), C. E. Rebar; V. Haysen; K. F. Koopman et al., eds., Lontra canadensis, 587, pp. 1–8),, retrieved October 4, 2012 
  3. Ellis, E. (2003), Lontra canadensis, Animal Diversity Web.,, retrieved September 23, 2012