Mammals of the Adirondacks:
North American River Otter (Lontra canadensis)

Mammals of the Adirondack Park: North American River Otters on Heron Marsh (6 October 2014).
Mammals of the Adirondacks: The basic social unit of the North American River Otter is a family group consisting of the female and her young, such as this group of three otters frequently seen at the Paul Smiths VIC during the fall of 2014. North American River Otters on Heron Marsh (6 October 2014).

North American River Otters (Lontra canadensis) are members of the weasel family who grow three to four feet long and weigh 10 to 30 pounds. The head is broad and flat, with short, rounded ears. River otters have glossy, brown guard hairs over a short, oily underfur. River otters are a semi-aquatic mammal; they are swift and agile swimmers who make use of a long, muscular tail and webbed feet. They can remain submerged for several minutes at a time.

North American River Otters usually do not survive more than ten years in the wild, although they may live up to twenty years in captivity. This species is also known as Northern River Otter, Canadian Otter, Land Otter, and Fish Otter.


History of the North American River Otter

Mammals of the Adirondack Park: North American River Otter on Heron Marsh at the Paul Smiths VIC (14 May 2016).
Mammals of the Adirondacks: North American River Otters often make their home on beaver ponds and marshes. North American River Otter on Heron Marsh at the Paul Smiths VIC (14 May 2016).
At one time, North American River Otters could be found in all watersheds in New York State, but unregulated trapping, habitat destruction, and water pollution reduced their numbers. Legal protection for these animals was first established in 1936, leading to a resurgence in otter numbers. Until the early 1990s, however, few river otters could be found in the western half of the state. In response, the New York River Otter Project was established in the late 1990s; it involved trapping river otters in eastern New York and releasing them in the central and western part of the state.

Range and Habitat of the North American River Otter

North American River Otters occur in much of Canada and the United States, except for portions of the Southwest, and in Mexico in the Rio Grande and Colorado River delta areas.

This species can be found living in rivers, lakes, ponds, small streams, marshes, and other inland wetlands. River otters are often found in the same freshwater wetlands as beaver. Dens are usually found near water and often have underwater entrances. Otters generally do not excavate their own dwellings, but use the burrows of beaver or other mammals for their den sites.

Diet of North American River Otters

Mammals of the Adirondack Park: North American River Otter scent marking her territory on Heron Marsh at the Paul Smiths VIC (9 May 2015).
Mammals of the Adirondacks: North American River Otters scent mark using scent glands near the base of their tails, producing a strong, musky odor. North American River Otter scent marking her territory on Heron Marsh at the Paul Smiths VIC (9 May 2015).

North American River Otters are carnivores and will consume almost anything they can catch. They are primarily visual predators. However, they also have motion-sensitive whiskers which enable them to forage in murky waters and find their prey by sensing vibrations with their whiskers. Fish comprise the majority of their diet, but they will also take crustaceans and other aquatic invertebrates.

North American River Otter Breeding

North American River Otter young are born in April or May. Adults provide them food for up to 10 months. Males or a non-breeding female may remain with the family group temporarily. Juvenile otters usually remain with the female until she bears her next litter the following spring, dispersing when they are 12 to 13 months old. The main social unit is the family, generally one adult female and her young.

North American River Otter Behavior

North American River Otters are usually nocturnal, with peak activity occurring around midnight and just before dawn. There is no hibernation period. They are active year-round and may be more active during the winter, when they reportedly become more active during the daytime hours.

  • Otter Play Time: Highly energetic, river otters spend much of their time playing. They may be observed touching, shoving, tossing, and manipulating prey, stones or other objects, or tobogganing down mud or snow slides.
  • Otter Vocalization: Otters are quite vocal, using chirping and humming sounds as contact calls. As you move through otter habitat, listen for the squeaks and chirps that otters use to keep in contact with each other.

Where to See North American River Otters

Mammals of the Adirondack Park: North American River Otters on Heron Marsh (4 September 2015).
Mammals of the Adirondacks: Look for otters flashing in and out of the vegetation on the edge of the Heron Marsh or feeding on fresh-water mussels, clams, and fish. North American River Otters on Heron Marsh (4 September 2015).

The Tri-Lakes area offers two convenient places to see and learn about North American River Otters.

  • To see North American River Otters in captivity, visit the Wild Center in Tupper Lake. The Wild Center currently has three otters – Louie, Squirt, and Remington – who were either rescued and saved by rehabilitators or born in captivity in other zoos. The Otter Falls exhibit area gives visitors close-up views of the otters swimming, eating and playing. 
  • Catching a glimpse of otters in the wild is a chancier venture. One likely place is Heron Marsh at the Paul Smiths VIC, where otters are protected because hunting and trapping are not allowed. The best places for viewing these creatures are from the overlooks on the Heron Marsh Trail (particularly on the raised tower), on the floating bridge on the Woods and Waters Trail, and at Shingle Mill Falls on the Loggers Loop Trail. Otters have also been seen from the viewing platforms on the Barnum Brook Trail. Look for glimpses of their dark, shiny brown heads, moving quickly through the water on Heron Marsh. You might also spot an otter by looking for its wake in the water. At the VIC, young otters may be seen playing on Heron Marsh, especially during the fall. The best time to catch sight of an otter at the VIC is early morning or late afternoon.

You can also watch for signs of otter activity when the animals themselves are not visible. During winter walks, look for evidence of otter play in the form of slide marks in the snow. At the VIC, a good place to be on the look-out for such marks is at the marsh outlet at Shingle Mill Falls, where otters have tobogganed over the falls.


References

New York State Department of Environmental Conservation. River Otter. Retrieved 28 March 2017.

New York State Department of Environmental Conservation. Watchable Wildlife: River Otter. Retrieved 6 October 2014.

New York State Department of Environmental Conservation. River Otters (video). Retrieved 6 October 2014.

State University of New York. College of Environmental Science and Forestry.  River Otter. Retrieved 28 March 2017.

United State Environmental Protection Agency. Wildlife Exposure Factors Handbook. pp. 261-273.Retrieved 28 March 2017.

Steve Boyle. North American River otter (Lontra canadensis): A Technical Conservation Assessment (USDA Forest Service, 2 September 2006).

United States Department of Agriculture. Fire Effects Information System (FEIS).  Species Reviews. Lontra canadensis. Retrieved 28 March 2017.

Smithsonian National Museum of Natural History. North American Mammals. Lontra canadensis.  Retrieved 28 March 2017.

Serge Lariviere and Lyle R. Walton, "Lontra canadensis," Mammalian Species, No. 587, 1 June 1998, pp.1-8. Retrieved 28 March 2017.

Defenders of Wildlife.  Animal Fact Sheets.  North American River Otter.  Retrieved 28 March 2017.

National Wildlife Federation. Wildlife Library. North American River Otter.  Retrieved 28 March 2017.

IUCN Red List of Threatened Species. Lontra canadensis.  Retrieved 28 March 2017.

University of Michigan. Animal Diversity Web.  Lontra canadensis.  Retrieved 28 March 2017.

National Geographic. North American River Otter.  Retrieved 28 March 2017.

William K. Chapman.  Mammals of the Adirondacks. A Field Guide (North Country Books, 1991), pp. 13, 104, 106, 146, Plate 17.

James M. Ryan. Adirondack Wildlife. A Field Guide (University of New Hampshire Press, 2008), pp. 205-206.

Donald W. Stokes and Lillian Q. Stokes.  A Guide to Animal Tracking and Behavior (Little, Brown and Company, 1986), pp. 354-363.

Curt Stager. Field Notes from the Northern Forest (Syracuse University Press, 1998), pp. 166-167.

Mammals of the Adirondack Park

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