Lontra canadensis

River Otters can be thought of - and in a very real sense are - semi-aquatic weasels. Like fishers, martens, and mink, they have long, slender bodies, short limbs, and a short face, plus a set of adaptations for their aquatic lifestyle: an oily, waterproof coat, webbed toes, and small external ears. River Otters are good swimmers and divers, able to stay underwater for up to eight minutes. They feed on crayfish, crabs, fish, birds, small mammals, and some aquatic plants. They once lived in streams, rivers, lakes, swamps, and coastal areas throughout Canada and the United States. Now they are gone from the central and eastern United States, and extinct or rare in Arizona, Colorado, Indiana, Iowa, Kansas, Kentucky, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, Tennessee, Utah, and West Virginia. Scientific studies have shown them to be sensitive to pollution. Still these animals are commercially harvested: 20,000 - 30,000 are taken annually for their lustrous fur.

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North American river otters occur throughout Canada and the United States, except for areas of southern California, New Mexico, and Texas, and the Mohave desert of Nevada and Colorado. In Mexico they are found in the delta areas of the Rio Grande and Colorado river. Otters were locally extirpated from portions of their range but reintroduction and conservation efforts have helped stabilize populations.

Biogeographic Regions: nearctic (Native )

The northern river otter historically occurred over much of the North American
continent. Present distribution of the northern river otter extends from 25
degrees N. in Florida to beyond 70 degrees N. in Alaska, and from
eastern Newfoundland to the Aleutian Islands [4]. Northern river otters have
been extirpated or are rare in Arizona, Colorado, Indiana, Iowa, Kansas,
Kentucky, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South
Dakota, Tennessee, Utah, and West Virginia. They are still relatively
abundant along the coasts of the Atlantic Ocean and the Gulf of Mexico,
throughout the Pacific Northwest and Great Lakes states, and across most
of Canada and Alaska. Populations are listed as stable or increasing in
Alabama, Alaska, Arkansas, Connecticut, Delaware, Florida, Georgia,
Idaho, Louisiana, Maryland, Massachusetts, Michigan, Minnesota,
Mississippi, Montana, New Hampshire, New York, North Carolina, Oregon,
Rhode Island, Texas, Vermont, Washington, and Wisconsin [4].

AL AK AZ AR CA CO CT DE FL GA ID IL IN IA KS KY LA ME MD MA MI MN MS MO MT NE NV NH NJ NM NY NC ND OH OK OR PA RI SC SD TN TX UT VT VA WA WV WI WY AB BC MB NB NF NT NS ON PE PQ SK YK

L. 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 1660W 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 (Lariviere 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 are 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).

North American river otters occur throughout Canada and the United States, except for areas of southern California, New Mexico, and Texas, and the Mohave desert of Nevada and Colorado. In Mexico they are found in the delta areas of the Rio Grande and Colorado river. Otters were locally extirpated from portions of their range but reintroduction and conservation efforts have helped stabilize populations.

Biogeographic Regions: nearctic (Native )

North America (Alaska west across northern Canada and the US to Nova Scotia)

Gulf of Maine, North West Atlantic

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Throughout most of North America north of Mexico, except the extreme southwestern U.S. Extirpated from large areas of the interior U.S. following European colonization. Has been reintroduced in some parts of the range (e.g., Colorado, Virginia).

Historically, river otters ranged over the most of the United States and Canada, but became rare, or were extirpated during the fur trading period. Presently, they are distributed from approximately 25? N latitude in Florida through the Gulf of Mexico, to 70? N latitude in Alaska; and from eastern Newfoundland west throughout Canada, Alaska and the Aleutian Islands (Chapman and Feldhamer 1982). River otters occur throughout the Indian River Lagoon system.

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. Their whiskers are long and thick. 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.

Range mass: 5 to 14 kg.

Range length: 889 to 1300 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

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.

Range mass: 5 to 14 kg.

Range length: 889 to 1300 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Length: 131 cm

Weight: 13600 grams

Captive otters have been documented to live 16 years or more (Banfield 1974). Body size of adults is generally 1 m (3 feet) or more in length, including the tail. The tail measures as much as 31-46 cm (12 - 18 inches). Adults can weigh from 3-15 kg (7-35 pounds), with males typically outweighing females.

Sexual Dimorphism: Males are larger than females.

Length:
Range: 889-1,300 mm

Weight:
Range: 5-14 kg

Distinguishing characteristics: long streamlined animals with a thick tapered tail and short legs, wide, rounded head, small ears, and nostrils that can be closed underwater. long thick whiskers. they are dark brown to black above a ligther color ventrally. throat and cheeks are usually a golden. The feet have claws and are completely webbed.

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.

Habitat Regions: temperate ; terrestrial

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Wetlands: marsh ; swamp ; bog

Other Habitat Features: riparian ; estuarine

Northern river otters inhabit a variety of riparian plant communities. These
communities are often dominated by willows (Salix spp.), cottonwoods
(Populus spp.), birches (Betula spp.), and spruce (Picea spp.). Other
vegetation common in northern river otter habitats includes cattails (Typha
spp.), red-osier dogwood (Cornus sericea), black hawthorn (Crataegus
douglassi), common snowberry (Symphoricarpos albus), grasses, horsetails
(Equisetum spp.), bulrushes (Scirpus spp.), and sedges (Carex spp.)
[3,6,19].

Habitat and Ecology

Systems

• Terrestrial
• Freshwater
• Marine

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.

Habitat Regions: temperate ; terrestrial

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Wetlands: marsh ; swamp ; bog

Other Habitat Features: riparian ; estuarine

Riparian zones, usually no more than a few hundred meters from water unless they are moving between rivers or lakes. River otters can tolerate a variety of environments including very cold and hot areas, high elevations, and coastal waters (rarely).

Depth range based on 75 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 0 - 0
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Freshwater

Comments: Streams, lakes, ponds, swamps, marshes, estuaries (in some areas), beaver flowages, exposed outer coast (Pacific Northwest, Alaska). When inactive, occupies hollow log, space under roots, log, or overhang, abandoned beaver lodge, dense thicket near water, or burrow of other animal; such sites also are used for rearing young. Highly associated with beaver on Mount Desert Island, Maine (Dubuc et al. 1990). Uses traditional haul-out sites along the banks of aquatic habitats. May travel long distances overland, particularly in snow.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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.

Animal Foods: birds; mammals; amphibians; fish; eggs; insects; terrestrial non-insect arthropods; aquatic crustaceans

Plant Foods: leaves; roots and tubers; macroalgae

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.

Animal Foods: birds; mammals; amphibians; fish; eggs; insects; terrestrial non-insect arthropods; aquatic crustaceans

Plant Foods: leaves; roots and tubers; macroalgae

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)

Comments: Feeds opportunistically on aquatic animals, particularly fishes (mostly slow-moving, mid-size species), frogs, crayfish, turtles, insects, etc., sometimes birds and small mammals. In coastal waters eats marine species (Bowyer et al. 1995). Commonly preys on nesting seabirds in some areas (e.g., Alaska islands). See Toweill and Tabor 1982 for many further details.

In the absence of large mammalian predators such as wolves and bears, river otters are top predators in some of the ecosystems where they occur, including the Indian River Lagoon. Though often blamed for damaging or depleting commercial fish stocks, the bulk of the diet consists of slow moving or schooling non-game fish species (Chapman 1982). Common prey types include: cyprinids, suckers (Catostomus spp.), chubs (Semotilus spp.), shiners (Notropis spp.), catfish (Ictalurus spp.), and perch (Perca spp.) (Banfield 1974; Chapman 1982).Besides non-game fish, river otters also consume crustaceans (primarily crayfish), amphibians, insects, small birds and waterfowl, mammals and plants (Meehan 1974; Chapman 1982; Davis et al. 1992).Competitors: River otters practice mutual avoidance behaviors in order to reduce intraspecific competition. Melquist and Hornocker (1983) observed otters to practice "personal space dispersion" whereby individuals defended territories based on their current location, rather than upon fixed environmental parameters. They postulated that this behavior probably had the effect of reducing direct competition for resources. Mutual avoidance is practiced primarily through vocalization and scent marking rather than by direct confrontation.Predators: River otters have few natural predators other than man; however, young otters are placed at risk for predation from foxes, bobcats, wolves, coyotes and snapping turtles when they leave water to traverse land areas.Habitats: River otters have somewhat large home ranges of approximately 8-78 square km. They utilize a wide variety of riparian communities including cattails (Typha spp), sedges (Carex spp.) and grasslands (Chabreck 1971; Dronkert-Egnew 1991; Waller 1992).Lontra canadensis is well adapted to aquatic habitats from marine to fresh water. Optimum otter habitat, according to Chapman (1982) is in highly vegetated areas having slow moving waters with deep pools, and abundant fish. Otters tend to be most abundant in coastal areas, or in the lower portions of rivers and estuaries. The total habitat area must provide otters with escape cover, den sites, and resting sites.Otters do not dig their own dens; rather, they rely on those dug by other animals, or on natural shelters such as the hollows of trees, tall marsh grasses, or riverbank thickets (Banfield 1974; Chapman 1982).Activity Time: Lontra canadensis is primarily nocturnal. However, it is also highly active in the early morning and in late afternoon (Banfield 1974).

North American river otters are important predators of fish and aquatic invertebrates.

North American river otters are sometimes taken by bobcats, coyotes, birds of prey, alligators, 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.

Known Predators:

• bobcats (Lynx_rufus)
• coyotes (Canis_latrans)
• birds of prey (Falconiformes)
• American alligators (Alligator_mississipiensis)

Although essentially safe from predators while in water, northern river otters
are considerably more vulnerable when they travel overland between
lakes, ponds, and steams [14]. Bobcats (Felis rufus), dogs (Canis
familiaris), coyotes (C. lutrans), foxes, gray wolves (C. lupus), and
American alligators (Alligator mississippiensis) have all been reported
to kill northern river otters [4,14,15]. In addition, it is likely that other
predators, including cougars (F. concolor), black bears (Ursus
americanus), American crocodiles (Crocodylus acutus), and some large
raptors, also kill northern river otters on occasion. No predator has been shown
to have a serious impact on northern river otter populations, and most predation
is probably directed toward young northern river otters [4].

North American river otters are important predators of fish and aquatic invertebrates.

North American river otters are sometimes taken by bobcats, coyotes, birds of prey, alligators, 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.

Known Predators:

• bobcats (Lynx rufus)
• coyotes (Canis latrans)
• birds of prey (Falconiformes)
• American alligators (Alligator mississipiensis)

Lontra canadensis is prey of:
Lynx rufus
Canis latrans
Alligator mississippiensis
Falconiformes

This list may not be complete but is based on published studies.

Lontra canadensis preys on:
non-insect arthropods
Actinopterygii
macroalgae
Arthropoda
Crustacea
Insecta
Amphibia
Aves
Mammalia
Chrysemys picta
Anas fulvigula
Actitis macularia
Larus californicus
Ondatra zibethicus
Alligator mississippiensis

This list may not be complete but is based on published studies.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: The large range likely is divisible into at least 100 element occurrences.

10,000 to >1,000,000 individuals

Comments: Total population size is unknown but may exceed 10,000 individuals.

Chapman and Feldhamer (1982) suggested that otter populations in many areas are apparently stable and may be slowly increasing. Large populations of river otter exist in many states throughout the northern U.S. (including Alaska) and Canada where the river otter is still trapped for its fur. In Florida, however, river otters are not considered abundant in the Indian River Lagoon area. Intense pressure from coastal development and resulting loss of habitat have caused otter populations in this area to decline. There are apparently several population strongholds including the Merritt Island National Wildlife Refuge -Canaveral National Seashore complex, as well as other relatively undeveloped areas (Ehrhart 1995).Locomotion: Lontra canadensis actively swims, and crawls. They are capable of achieving running speeds of 29 km/hr (18 miles/hr), and have been observed to remain submerged for as long as 8 minutes.

Home range typically is linear; 20-30 miles for a pair or male; less for females with young (Jackson 1961). May hunt over as much as 80-100 km of stream during the course of one year. In coastal Alaska, summer home range size averaged around 20 km of shoreline in males, 10 km in females, with ranges twice as large in oiled areas (Bowyer et al. 1995).

Population density of one per 2.2 miles has been recorded (Baker 1983). Density was estimated at one otter per 86 ha of coastal marsh in Louisiana (Shirley et al. 1988). In Idaho, density was one family group and 1-3 subadults or nonbreeding adults per 15 km of waterway, plus one breeding adult male for each 20-30 km of waterway (see Toweill and Tabor 1982). Density in coastal areas of the Gulf of Alaska was 0.30-0.85 otters/km of shoreline (Testa et al. 1994, Bowyer et al. 1995).

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.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

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.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

Comments: Active in winter, even in fresh deep snow. May be active at any time of day. In Idaho, most active from dawn to midmorning and in the evening (see Toweill and Tabor 1982).

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

Range lifespan
Status: captivity: 21 (high) years.

Typical lifespan
Status: wild: 8 to 9 years.

Average lifespan
Status: wild: 8-9 years.

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

Range lifespan
Status: captivity: 21 (high) years.

Typical lifespan
Status: wild: 8 to 9 years.

Average lifespan
Status: wild: 8-9 years.

Maximum longevity: 27 years (captivity) Observations: There is a delayed implantation and thus the total gestation time varies from 290 to 380 days. The actual embryonic development takes about 60-63 days (Ronald Nowak 2003). One wild born female was as old as 27 when she died in captivity (Richard Weigl 2005).

Males and females only come together during the mating season. Males usually mate with several females that live in or near their own territory.

Mating System: polygynous

Males and females come together to breed in late winter or early spring. Pregnancy lasts two months, but the young may be born up to a year after mating because these otters delay the implantation of the fertilized egg. 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 mother's home range at from 6 months to a year old. Sexual maturity is reached at 2 to 3 years of age.

Breeding interval: Breeding occurs once yearly.

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

Range number of offspring: 1 to 6.

Average number of offspring: 2-3.

Average gestation period: 2 months.

Average weaning age: 3 months.

Range time to independence: 6 to 12 months.

Range age at sexual or reproductive maturity (female): 2 to 3 years.

Range age at sexual or reproductive maturity (male): 2 to 3 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); viviparous ; delayed implantation

Average birth mass: 140 g.

Average gestation period: 62 days.

Average number of offspring: 2.5.

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.

Parental Investment: altricial ; female parental care

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.

Mating System: polygynous

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.

Breeding interval: Breeding occurs once yearly.

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

Range number of offspring: 1 to 6.

Average number of offspring: 2-3.

Average gestation period: 2 months.

Average weaning age: 3 months.

Range time to independence: 6 to 12 months.

Range age at sexual or reproductive maturity (female): 2 to 3 years.

Range age at sexual or reproductive maturity (male): 2 to 3 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); viviparous ; delayed implantation

Average birth mass: 140 g.

Average gestation period: 62 days.

Average number of offspring: 2.5.

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.

Parental Investment: altricial ; female parental care

Implantation is delayed 8 months or more. Gestation, including delayed implantation, lasts 9-12 months. In many areas, births peak in late winter-early spring; parturition dates may not be closely synchronized within a given population. Litter size is 1-6 (average 2-3); 1 litter per year. Young may first enter water at about 7 weeks, are weaned at about 3 months, stay with mother for about a year. Male may rejoin family after young leave den. Females breed for the first time at 2 years. Males become sexually mature at 2 years, but may not breed successfully until 5-7 years old. Females evidently breed in alternate years in some areas (e.g., Alabama, Georgia), every year in Oregon (see Toweill and Tabor 1982).

Breeding occurs in late winter and early spring (Banfield 1974; Chapman and Feldhamer 1982). Females are considered sexually mature at 2 years of age, but do not necessarily breed upon first reaching maturity. Some evidence suggests that females do not breed every year (Melquist and Hornocker 1983; Dronkert-Egnew 1991). Males mature at approximately 2 years of age, but may not successfully breed until they are 5-7 years old (Chapman and Feldhamer 1982). Copulation occurs in water.

There is much discrepancy in the scientific literature regarding the length of river otter gestation periods, with reports ranging from 288 - 375 days (Chapman 1974; Wren 1991). This extreme difference has been attributed to a process known as delayed implantation, in which young are born following a period of arrested development. In this process, fertilized eggs develop to the blastocyst stage, and then remain floating in the uterus for a variable period of time before implanting into the uterine wall. Litters are born nearly a year following conception, generally from November to May; though in the Pacific northwest, pups are delivered from March through May. The actual gestation period following implantation is estimated to be 60-62 days (Chapman and Feldhamer 1982; Dronkert-Egnew 1991; Nebraska Game and Parks Commission 2001).Litter size ranges from 1- 6 pups per litter, with 2-4 being most common (Chapman 1982). Pups open their eyes at 21-35 days. At 25-42 days, they begin to play. Parents introduce pups to water at 48 days, and they begin to venture outside the den alone at 59-70 days. Pups are fully weaned by 91 days, and will leave parents at approximately 1 year old (Chapman 1982).

Information on state- and province-level protection status of animals in the
United States and Canada is available at NatureServe, although recent
changes in status may not be included.

Not listed

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 2004
  Least Concern
• 2000
  Lower Risk/least concern
• 2000
  Lower Risk/least concern

Northern river otters are listed in Appendix II of CITES. Populations were once extirpated through many parts of their range, especially around heavily populated areas in the midwestern and eastern United States. Population trends have stabilized in recent years and reintroduction and conservation efforts have resulted in recolonization of areas where they were previously extirpated. Northern river otter populations are still considered vulnerable or imperiled throughout much of their range in midwestern United States and the Appalachian mountains. They are presumed extirpated in New Mexico and population status in South Carolina and Florida has not yet been reviewed.

US Federal List: no special status

CITES: appendix ii

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Large range in much of North America north of Mexico; population trend probably is relatively stable; recent reintroduction and management efforts have improved conservation status.

Population

Population Trend

Global Short Term Trend: Relatively stable (=10% change)

Comments: Population trend probably is relatively stable overall.

Major Threats

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: Local/regional declines were caused by unregulated trapping and degradation of riverine/riparian habitat. Oil contamination resulted in reduced habitat availability in Alaska (Bowyer et al. 1995).

Conservation Actions

Management Requirements: Suseptible to overharvest (Toweill and Tabor 1982).

See Berg (1982) for information on reintroduction. See Tango et al. (1991) for a review of information on reproduction by reintroduced otters. Sources of otters for reintroductions should be based on documented patterns of genetic variation, which do not concur very well with nominal subspecies delineations (Serfass et al. 1998).

Management Research Needs: Refine techniques for successful reintroduction (e.g., reducing dispersal from reintroduction area).

Biological Research Needs: See element stewardship (ES) files.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Protected in several national and state parks and refuges.

Needs: Maintain productive aquatic habitats. Prevent excessive harvest. Support reintroduction and habitat restoration efforts.

North American river otters generally do not have adverse affects on humans.

North American river otters are important parts of healthy, aquatic ecosystems.

North American river otters have been hunted for many years for their attractive and durable fur. In the 1983-84 hunting season, 33,135 otters were taken with an average selling price of $18.71 per pelt. Otters are stll an important source of income for many people in Canada and the western United States. River otters also eat "trash fish" that compete with more economically desirable game fish.

Positive Impacts: body parts are source of valuable material

Comments: Harvested for fur. In the early to mid-1970s, U.S. harvest was about 11,000-19,000, Canadian harvest was about 15,000-18,000 (Toweill and Tabor 1982). U.S. harvest recently has been largest in Louisiana (about 7500 pelts annually in the 1970s and early 1980s) (Shirley et al. 1988).

Lontra canadensis is a top predator in the Indian River Lagoon system.Benefit in IRL: Their aesthetic value aside, river otters may help reduce direct competition between commercially valuable fish species and other fishes. Otters have historically been blamed for depleting game fish stocks; however, they may actually be of benefit to commercial species due to their preference for slow moving, non-game species of fishes. Through removal of non-game fishes, commercial species thus enjoy reduced competition for food (Davis et al. 1992).River otter fur is still highly prized today in the fur trade and nearly all U.S. states allow the export of otter pelts, subject to regulation by state wildlife authorities. In some states, river otter populations are low enough to have gained them threatened or endangered status. They are thus protected and managed for in these areas. However, in all Canadian provinces, Alaska, and approximately half of the remaining U.S. states otters are still trapped seasonally under highly regulated conditions. Perhaps surprisingly, Louisiana generally has the highest harvest of river otters in the U.S., with annual totals sometimes exceeding 10,000 animals (Nebraska Game and Parks Commission 2001). River otter pelts in 2001 were valued at an average of $48.00 USD (North American Fur Auctions 2001).