Lontra canadensis


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Lontra canadensis
Species Authority: (Schreber, 1777)
Common Name(s):
English North American River Otter, Northern River Otter, North American Otter
French Loutre de rivière, Loutre du Canada
Spanish Nutria de Canadá, Nutria Norteamericana
Lutra canadensis Schreber, 1777
Taxonomic Notes: River otters from North and South America were recognized as distinct from their European river otters by Van Zyll de Jong (1987). However, the genus name Lontra is rarely used in the present literature, and numerous authors still use Lutra (Kellnhauser 1983). Herein, Lontra is used in concordance with Van Zyll de Jong (1972, 1987) and Wozencraft (2005).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2015
Date Assessed: 2014-06-01
Assessor(s): Serfass, T., Evans, S.S. & Polechla, P.
Reviewer(s): Duplaix, N. & Hussain, S.A.
The North American River Otter is considered to be Least Concern as it is not currently declining at a rate sufficient for a threat category. By the early 1900s, river otters had declined throughout large portions of their historic range in North America. However, improvements in water quality (through enactment of clean water regulations) and furbearer management techniques have enabled river otters to reclaim portions of their range in many areas. Reintroduction projects have been particularly valuable in restoring otter populations in many areas of the United States. However, river otters remain rare or absent in the southwestern United States and water quality and development limit recovery of populations in some areas. The species is widely distributed throughout its range. In many places the populations have re-established themselves because of conservation initiatives (Polechla 1990). There is an ongoing discussion about the problem of reintroduction of river otters. In recent years it is feared that it may contaminate the genetic structure of the native population.
2004 Least Concern

Geographic Range [top]

Range Description:Lontra canadensis currently occurs throughout the United States of America and Canada. Originally this species is thought to have ranged from 250-700°N latitude and from 530 to 1660°W longitude. In the USA, this species is present in states bordering the Great Lakes, Atlantic Ocean and Gulf of Mexico, and in the forested regions of the Pacific coast in North America (Larivière and Walton 1998). It is also present throughout Alaska, including the Aleutian Islands and the north slope of the Brooks Range (Magoun and Valkenburg 1977). Urbanization and pollution caused reductions in range area and the species is now absent or rare in Arizona, Hawaii, Indiana, Iowa, Kansas, Kentucky, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, Tennessee, and West Virginia (Melquist and Dronkert 1987, Park 1971, Polechla 1990). Reintroductions have expanded the distribution of this species in recent years, especially in the Midwestern United States (Melquist and Dronkert 1987). In Canada, North American River Otters occupy all provinces and territories, except for Prince Edward Island (Melquist and Dronkert 1987).
Canada (Alberta, British Columbia, Labrador, Manitoba, New Brunswick, Newfoundland I, Northwest Territories, Nova Scotia, Nunavut, Ontario, Prince Edward I. - Regionally Extinct, Québec, Saskatchewan, Yukon); United States (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Hawaiian Is., Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico - Possibly Extinct, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming)
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: By the early 1900s, unregulated trapping, water pollution, and other degradations of aquatic and riparian habitats had caused otter populations to decline throughout most of their historic range (Nilsson 1980, Toweill and Tabor 1982, Melquist and Dronkert 1987). Improvements in water quality and furbearer management strategies, including implementation of reintroduction projects, have enabled the re-establishment of otter populations to various aquatic habitats in portions of their former range. Reintroduction projects have been especially useful in restoring otter populations to riverine habitats in interior regions.

Methods for determining relative abundance of North American River Otters include track counts in the snow (Reid et al. 1987, St-Georges et al. 1995), radioactive isotopes (Knaus et al. 1983, Testa et al. 1994), catch/unit effort (Chilelli et al. 1996), and scent-station surveys (Humphrey and Zinn 1982). Density estimates of river otters range from one otter/1.25-3.60 km of coastline in Alaska (Testa et al. 1994) to one otter/3.9 km of waterway in Idaho (Melquist and Hornocker 1983).
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: Historical records indicate that river otters were well established throughout most major drainages in the continental United States and Canada prior to European settlement (Hall 1981). The continent’s largest otter populations occurred in areas with an abundance and diversity of aquatic habitats such as coastal marshes, the Great Lakes region, and glaciated areas of New England (Nilsson 1980, Toweill and Tabor 1982, Melquist and Dronkert 1987). In addition, riverine habitats in interior regions supported smaller, but viable, otter populations (Nilsson 1980).

North American River Otters prefer bog lakes with banked shores containing semi-aquatic mammal burrows and lakes with Beaver (Castor canadensis) lodges, and they avoid water bodies with gradually sloping shorelines of sand or gravel (Reid et al. 1994b). In Maine, use of watersheds by river otters is negatively associated with the proportion of mixed hardwood-softwood stands in forested areas adjacent to waterways and positively associated with the number of Beaver flowages, watershed length, and average shoreline diversity (Dubuc et al. 1990). In Idaho, river otters prefer valley over mountain habitats, and they select valley streams over valley lakes, reservoirs, and ponds (Melquist and Hornocker 1983). Logjams are used intensively where present (Melquist and Hornocker 1983). In Florida, abundance of North American Otters is lowest in freshwater marshes, intermediate in salt marshes, and highest in swamp forest. During the dry season, L. canadensis will retreat from marshland and move to permanent ponds where water is available and food is more concentrated (Humphrey and Zinn 1982). In Idaho and Massachusetts, habitat features preferred for latrine sites include large conifers, points of land, Beaver bank dens and lodges, isthmuses, mouths of permanent streams, or any object that protrudes from the water (Melquist and Hornocker 1983, Newman and Griffin 1994).

The diet of the North American River Otter is comprised mostly of fish that are abundant, mid-sized, and close to shore (Larsen 1984, Stenson et al. 1984), as well as amphibians (mostly frogs) and crustaceans (mainly crayfish) (Knudsen and Hale 1968, Reid et al. 1994a, Sheldon and Toll 1964). Small mammals, molluscs, reptiles, birds, and fruits are consumed opportunistically (Gilbert and Nancekivell 1982, Greer 1955, Hamilton 1961, Morejohn 1969, Verbeek and Morgan 1978, Wilson 1954). North American River Otters have few natural predators in the water: Alligators (Alligator mississippiensis), American Crocodiles (Crocodylus acutus), and Killer Whales (Orcinus orca). They are considerably more vulnerable on land or ice where Bobcats (Lynx rufus), Cougars (Felis concolor), Coyotes (Canis latrans), Domestic Dogs (Canis familiaris) and Wolves (Canis lupus) can kill adults (Melquist and Dronkert 1987, Melquist and Hornocker 1983, Route and Peterson 1991, Toweill and Tabor 1982). Most mortality, however, is human-related and includes trapping, illegal shooting, road kills, and accidental captures in fish nets or set lines (Jackson 1961, Melquist and Hornocker 1983).

North American River Otters can reach 13 years of age in the wild and up to 25 years of age in captivity (Melquist and Dronkert 1987, Stephenson 1977). Females usually do not reproduce until two years of age, although yearlings occasionally produce young (Docktor et al. 1987, Hamilton and Eadie 1964). Males are sexually mature at 2 years of age (Hamilton and Eadie 1964). North American river otters usually breed from December to April (Hamilton and Eadie 1964, Liers 1951), gestation lasts 61-63 days, and young are born between February and April (Hamilton and Eadie 1964, Melquist and Hornocker 1983). Litter size may reach five (Park 1971) but usually ranges from one to three (Docktor et al. 1987, Hamilton and Eadie 1964, Tabor and Wight 1977).
Systems: Terrestrial; Freshwater; Marine

Use and Trade [top]

Use and Trade: For Use and Trade information see under Threats.

Threats [top]

Major Threat(s): Threats to otter populations in North America vary among regions and are influenced by type, distribution, and density of aquatic habitats and characteristics of human activities. Prior to settlement of North America by Europeans, otters were widespread among aquatic habitats throughout most of the continent (Hall 1981). Unregulated trapping and loss or degradation of aquatic habitats through filling of wetlands and development of coal, oil, gas, tanning, timber, and other industries resulted in extirpations or declines in otter populations in many areas (Toweill and Tabor 1982, Melquist and Dronkert 1987). Nilsson (1980) reviewed the status of otters in the United States and determined that populations were extirpated in 11 states and had experienced severe declines in nine other states. The most severe population declines occurred in interior regions where fewer aquatic habitats supported smaller fewer otter populations. Although the distribution of otters became reduced in some regions of southern Canada, the only province-wide extirpation occurred on Prince Edward Island (Polechla 1990).

During the 1970s, improvements in natural resource management techniques coincided with increased concern about otter declines in North America (Endangered Species Scientific Authority 1978). Consequently, many wildlife management agencies developed strategies to restore or enhance otter populations, including the use of reintroduction projects (Ralls 1990, Serfass et al. 1993). Since 1976 over 4,000 otters have been reintroduced among 21 states. Also, 29 states and all Canadian provinces except Prince Edward Island have viable populations that sustain annual harvests. Annual harvest numbers of North American Otters are similar for Canada and the United States (Obbard 1987), with most pelts being used in the garment industry (Toweill and Tabor 1982). In the late 1970s, annual harvest in North America reached ca 50,000 pelts, for a value of US$3 million (Melquist and Dronkert 1987). Otters are incidentally harvested by traps set for Beavers (Toweill and Tabor 1982), and therefore management plans should consider both species simultaneously (Polechla 1990). While current harvest strategies do not pose a threat to maintaining otter populations, harvest may limit expansion of otter populations in some areas (Lariviére and Walton 1998).

Oil spills present a localized threat to otter populations, especially in coastal areas. Water pollution and other degradation of aquatic and wetland habitats may limit distribution of otters and pose long-term threats if enforcement of water quality standards are not maintained and enforced. Acid drainage from coal mines is a persistent water quality problem in some areas that eliminates otter prey prevents thereby inhibits recolonization or expansion of otter populations. Recently, there has been discussion of the long-term genetic consequences of reintroduction projects on remnant otter populations (Serfass et al. 1998). Similarly, many perceived threats to otters such as pollution and habitat alterations have not been rigorously evaluated.

The threat of disease to wild otter populations is poorly understood and has received little study (Serfass et al. 1995). Lontra canadensis may be victim of canine distemper (Harris 1968, Park 1971), rabies (Serfass et al. 1995), respiratory tract disease, and urinary infection (Hoover et al. 1984, Route and Peterson 1991). In addition, North American Otters can contract jaundice, hepatitis, feline panleucopenia, and pneumonia (Harris 1968). North American Otters host numerous endoparasites such as nematodes (Hoberg et al. 1997), cestodes (Greer 1955), trematodes (Hoover et al. 1984), the sporozoan Isopora (Hoover et al. 1984), and acanthocephalans (Hoberg et al. 1997, Hoover et al. 1984). Ectoparasites include ticks (Eley 1977, Serfass et al. 1992), sucking lice Latagophthirus rauschi (Kim and Emerson 1974), and the flea Oropsylla arctomys (Serfass et al. 1992).

Conservation Actions [top]

Conservation Actions: The species is included in CITES Appendix II. Additional research is needed to clearly delineate the impact that various forms of water pollution, agricultural and other development along riparian habitats, industrial and housing development in coastal areas, cumulative impacts related to loss or alterations of wetlands, large flood control structures, and interactions that these and other factors have on otter populations.

Bibliography [top]

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Citation: Serfass, T., Evans, S.S. & Polechla, P. 2015. Lontra canadensis. In: The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 28 August 2015.
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