Ondatra zibethicus

Muskrats are good swimmers thanks to their webbed feet and slightly flattened tail. They live around freshwater lakes and rivers with overgrown banks. They dig tunnels into these banks, with the entrance usually located underwater. During the winter, they build lodges from grass and reed. Their diet consists of aquatic plants, grass, plant roots, field crops and occasionally freshwater shells, crustaceans and fish. Muskrats are sometimes consumed by humans. Since muskrats live in water, they are considered equivalent to fish. That is why Catholics living in Detroit are allowed to eat them on days when fish is permitted but not meat.

Muskrats, so-called for their odor, which is especially evident during the breeding season, are highly successful semi-aquatic rodents. They occur in both brackish and freshwater lakes, ponds, streams, rivers, and marshes throughout much of North America, except in parts of the South where tidal fluctuation, periodic flooding, or drought limit their distribution. Muskrats have a variety of aquatic adaptations, including a rudder-like tail that is flattened side-to-side, partially webbed hind feet, and fur that traps air for insulation and buoyancy. Because their fur has commercial importance, they were taken to Japan, South America, Scandinavia, and Russia, and there are now feral populations in some places where they were introduced.

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Muskrats are only native to the Nearctic region, but have been introduced to the Palearctic and Neotropical regions. They are found throughout North America as far south as the southern United States, they are excluded from the southernmost portions of the United States by lack of appropriate habitat. The placed muskrats have been introduced to are Japan, parts of South America, Scandinavia, and Russia.

Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); neotropical (Introduced )

Common muskrats are distributed across North America from northern Alaska and
Canada south to parts of the Gulf Coast and northern portions of Mexico
[1]. They are found in northern and central California, parts of
southern Arizona, northern Utah and Nevada, most of New Mexico, the
Texas Panhandle, and eastern Texas, and a small part of western Texas
and the Louisiana coast. Common muskrats are not found in Florida or coastal
Georgia and South Carolina [14]. Ranges for each subspecies are given
below [14]:

1. O. z. zibethicus - eastern U.S. and southeastern Canada
2. O. z. albus - Manitoba and adjacent central Canada
3. O. z. aquilonius - Labrador and adjacent Ungava and Quebec
4. O. z. bernardi - Colorado River areas of southeastern California,
southern Nevada, and western Arizona and Mexico
5. O. z. cinnamominus - Great Plains
6. O. z. goldmani - southwestern Utah, northwestern Arizona, and
southeastern Nevada
7. O. z. macrodon - mid-Atlantic Coast
8. O. z. mergens - northern Nevada and parts of adjacent states
9. O. z. obscurus - Newfoundland
10. O. z. occipitalis - coastal Oregon and Washington
11. O. z. osoyoosensis - Rocky Mountains and southwestern Canada
12. O. z. pallidus - southcentral Arizona and west-central New Mexico
13. O. z. ripensis - southwestern Texas and southeastern New Mexico
14. O. z. rivalicius - southern Louisiana, Mississippi coast,
western Alabama, and eastern Texas
15. O. z. spatulatus - northwestern North America
16. O. z. zalophus - southern Alaska

AL AK AZ AR CA CO CT DE 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 DC AB BC MB NB NF NT NS ON PE PQ SK YK MEXICO

This species occurs in North America, from northern Canada and Alaska south through the United States, except the arid regions of the southwest and Texas, and the Florida peninsula. Introduced to Czech Republic in 1905 in order to establish fur farms, it is now present throughout the Palaearctic, Mongolia, China, northeast Korea, and Honshu Island, Japan. Also introduced in Argentina (Musser and Carleton, 2005).

The muskrat is found in swamps, marshes, and wetlands from northern North America to the Gulf coast and the Mexican border. Early in the 20th century, muskrats were introduced to northern Eurasia (Baker, 1983).

Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); neotropical (Introduced )

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: North America, north to the treeline, including Newfoundland; south to the Gulf Coast, Rio Grande, and lower Colorado River valleys; introduced and now widespread in Old World.

Muskrats have large, robust bodies, with a total body length of twelve and a half inches. The tail is flat and scaly and is nine and a half inches in length. Muskrats have dense fur that traps air underneath for insulation and buoyancy. Their heads are very large and their ears are almost invisible underneath the fur. Muskrats have short legs and big feet; their rear feet are webbed for swimming. Adult muskrats have glossy upperparts that are dark brown, darker in winter and paler in the summer

Range mass: 680.0 to 1800.0 g.

Average mass: 1135.8 g.

Range length: 410.0 to 620.0 mm.

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 4.363 W.

Muskrats have large, robust bodies, with a total body length of twelve and a half inches. The tail is flat and scaly and is nine and a half inches in length. Muskrats have dense fur that traps air underneath for insulation and buoyancy. Their heads are very large and their ears are almost invisible underneath the fur. The whiskers are mediun size. Muskrats have short legs and big feet; the back feet are slightly webbed for swimming. Adult muskrats have glossy upperparts that are dark brown, darker in winter and paler in the summer (Baker, 1983).

Range mass: 680.0 to 1800.0 g.

Average mass: 1135.8 g.

Range length: 410.0 to 620.0 mm.

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 4.363 W.

Length: 62 cm

Weight: 1816 grams

Length:
Range: 410-620 mm

Weight:
Range: 680-1,800 g

Muskrats are semi-aquatic and prefer locations with four to six feet of water. Muskrats are found in ponds, lakes, and swamps, but their favorite locations are marshes, where the water level stays constant. Marshes provide the best vegetation for eating and constructing nests and burrows. Muskrats find shelter in bank burrows and nests that they build. Bank burrows are tunnels excavated in a bank. Nests are made by piling vegetation on top of a solid base, for example a tree stump, generally in 15 to 40 inches of water.

Habitat Regions: temperate

Aquatic Biomes: lakes and ponds; rivers and streams

Wetlands: marsh ; swamp ; bog

Common muskrats inhabit wetland plant communities comprised of cattail (Typha
spp.), bulrush (Scirpus spp.), sedge (Carex spp.), reed (Phragmites
spp.), cordgrass (Spartina spp.), saltgrass (Distichlis spicata), and
black rush (Juncus roemerianus) [1,14].

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Muskrats are found in wet environments, favoring locations with four to six feet of water. While muskrats are found in ponds, lakes, and swamps, their favorite locations are marshes, where the water level stays constant. Marshes provide the best vegetation for muskrats. They find shelter in bank burrows and their distinctive nests. Bank burrows are tunnels excavated in a bank. The nests of the muskrats are formed by piles of vegetation placed on top of a good base, for example a tree stump, generally in 15 to 40 inches of water (Baker, 1983).

Habitat Regions: temperate

Aquatic Biomes: lakes and ponds; rivers and streams

Wetlands: marsh ; swamp ; bog

Depth range based on 4 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.

Comments: Prefers fresh or brackish marshes, lakes, ponds, swamps, and other bodies of slow-moving water. Most abundant in areas with cattail. Rare or absent in large artificial impoundments where fluctuating water levels eliminate littoral zone plants (food supply) (Caire et al. 1989). Dens in bank burrow or conical house of vegetation in shallow vegetated water. Sometimes in uplands-Clough 1987.

See Clark (1994) for information on habitat selection in experimental marshes undergoing succession in Manitoba.

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.

Muskrats are mainly vegetarians but will eat animals as well. Muskrats consume about one-third of their weight every day. Their digestive system is designed for green vegetation. In the summer they eat the roots of aquatic plants. In the winter, they swim under the surface ice to get to the plants. Muskrats also eat agricultural crops.

Muskrats are mainly vegetarians but will eat animals as well. Muskrats consume about one-third of their weight every day. Their digestive system is designed for green vegetation. In the summer they eat the roots of aquatic plants. In the winter, they swim under the surface ice to get to the plants. Muskrats also eat agricultural crops (Baker, 1983).

Primary Diet: herbivore

Comments: Diet mainly consists of aquatic plants, particularly cattails (TYPHUS spp.), cordgrass, and bulrush. Also eats crustaceans and mollusks; may eat large numbers mussels in some areas (Hanson et al. 1989). Builds rooted feeding platforms. Eats mainly upland vegetation in some areas.

Common muskrat predators include humans, mink (Mustella vison), raccoon
(Procyon lotor), bobcat (Felix rufus), house cat (F. domesticus),
domestic dog (Canis familiaris), coyote (C. latrans), red fox (Vulpes
vulpes), barn owl (Tyto alba), barred owl (Strix varia), great horned
owl (Bubo virginianus), northern harrier (Circus cyaneus), bald eagle
(Haliaeetus leucocephalus), eastern cottonmouth (Agkistrodon
piscivorus), alligator (Alligator mississippiensis), snapping turtle
(Chelydra serpentina), bullfrog (Rana catesbeiana), garfish (Lepisosteus
spp.), bowfin (Amia calva), and largemouth bass (Micropterus salmoides)
[14]. Common muskrats will kill the young of other common muskrats when populations
are too dense.

Muskrats are very abundant in areas of good habitat, making them important prey animals for predator populations. By grazing on vegetation, muskrats influence the composition of local plant communities.

Muskrats are excellent swimmers and can evade many predators by escaping into water or into their burrows and nests. They can remain under water for up to 15 minutes.

Known Predators:

• American minks (Neovison vison)
• raccoons (Procyon lotor)
• Northern river otters (Lontra canadensis)
• coyotes (Canis latrans)
• barn owls (Tyto alba)
• barred owls (Strix varia)
• northern harriers (Circus cyaneus)
• American alligators (Alligator mississippiensis)
• cottonmouth water moccasins (Agkistrodon piscivorus)

Ondatra zibethicus is prey of:
Bubo virginianus
Agkistrodon piscivorus
Circus cyaneus
Tyto alba
Strix varia
Lontra canadensis
Mustela vison
Procyon lotor
Canis latrans
Alligator mississippiensis

Based on studies in:
USA: California, Cabrillo Point (Grassland)

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

Generally solitary but several may use same general area; in winter several may congregate in single den. Territoriality common (Caire et al. 1989), mostly in breeding season.

Home range sizes relatively small; usually does not forage more than 11 m from home site (Baker 1983). In marginal areas, foraging excursions greater. Seasonal home range may range from less than 0.1 ha to several hectares (see Marinelli and Messier 1993). Home ranges generally less than 100 m in diameter (Takos 1944, Boutin and Birkenholz 1987). However, along linear waterways, home ranges average 411 meters long (Willner et al. 1980).

Populations fluctuate, density up to about 90/ha, usually much less (6/ha, 24/ha, and 36/ha in three studies cited by Marinelli and Messier 1993).

In Manitoba, spatial and temporal variation in vegetation response to flooding contributed to variation in the density dependence of both survival and recruitment; reductions in emergent vegetation caused by flooding resulted in decreased winter survival (Clark and Kroeker 1993).

Muskrats communicate by a secretion from their glands called musk. This scent also serves to warn intruders. They are capable of vocalizing by squeaks and squeals. Muskrats have poorly developed senses of sight, hearing, and smell.

Muskrats communicate by a secretion from their glands called musk. This scent also serves to warn intruders. They are capable of vocalizing by squeaks and squeals. Muskrats have poorly developed senses of sight, hearing, and smell.

Comments: Mainly nocturnal but frequently seen in daylight. Active year-round. Two peaks of activity: between 1600 and 1700 h and 2200-2300 hours (Stewart and Boder 1977).

Although muskrats have been known to live to 10 years old in captivity, they probably live about 3 years in the wild.

Range lifespan
Status: captivity: 10.0 (high) years.

Average lifespan
Status: wild: 3.0 years.

Average lifespan
Status: wild: 4.0 years.

Average lifespan
Status: wild: 3.0 years.

Average lifespan
Status: captivity: 10.0 years.

Although muskrats have been known to live to 10 years old in captivity, they probably live about 3 years in the wild.

Range lifespan
Status: captivity: 10.0 (high) years.

Average lifespan
Status: wild: 3.0 years.

Average lifespan
Status: wild: 4.0 years.

Average lifespan
Status: wild: 3.0 years.

Average lifespan
Status: captivity: 10.0 years.

Observations: There are conflicting reports about the longevity of the muskrat. In the wild, these animals live about 3 years. It has been suggested that they live up to 10 years in captivity (Ronald Nowak 1999). While this is plausible, it has not been confirmed. One specimen lived 5.8 years in captivity (Richard Weigl 2005). More studies are necessary to better estimate the longevity of the muskrat.

Southern muskrat populations can breed year round while northern populations only breed in the warmer months (March to August). Females are pregnant for 25 to 30 days and have usually 6 to 7 young per litter. Northern populations have larger litters. Young are born in a grass lined nest. When born, muskrats have short dark fur, closed eyes, and weigh around 22 grams. They are able to swim at 10 days and by 21 days can eat green vegetation. In 3 to 4 weeks young muskrats begin to feed on their own. They will reach their adult size by 200 days old.

Breeding season: Varies with latitude.

Range gestation period: 30.0 (high) days.

Range weaning age: 3.0 to 4.0 weeks.

Range age at sexual or reproductive maturity (female): 7.0 to 12.0 months.

Range age at sexual or reproductive maturity (male): 7.0 to 12.0 months.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous

Average birth mass: 22.72 g.

Average number of offspring: 6.7.

Young are cared for and nursed by their mothers in the nest until they are about 2 weeks old, when they begin to swim and eat vegetation. They are fully weaned by 3 to 4 weeks old and leave their mother's home range after their first winter, usually when they are less than a year old.

Parental Investment: altricial ; female parental care

Southern muskrat populations can breed year round while northern populations only breed in the warmer months (March to August). The gestation period is 29 - 30 days and the litter size averages around 6, with northern populations having larger litters. Young are born in a grass lined nest. When born, the muskrat has short dark fur, closed eyes, and weighs around 22 grams. They are able to swim at 10 days and by 21 days can eat green vegetation. In 30 days muskrats gain their independence and will reach adult size in 200 days (Baker, 1983).

Breeding season: Varies with latitude.

Range gestation period: 30.0 (high) days.

Range weaning age: 3.0 to 4.0 weeks.

Range age at sexual or reproductive maturity (female): 7.0 to 12.0 months.

Range age at sexual or reproductive maturity (male): 7.0 to 12.0 months.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous

Average birth mass: 22.72 g.

Average number of offspring: 6.7.

Young are cared for and nursed by their mothers in the nest until they are about 2 weeks old, when they begin to swim and eat vegetation. They are fully weaned by 3 to 4 weeks old and leave their mother's home range after their first winter, usually when they are less than a year old.

Parental Investment: altricial ; female parental care

Gestation lasts 28-30 days. Average of 2-3 litters/year. Litter size is 1-12 (usually averages about 5-6). Weaned and fairly independent after about 1 month. Sexually mature in 4-6 months. In Saskatchewan, polygyny was common (Marinelli and Messier 1993). Typically high rate of mortality in young.

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.

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern

Muskrats are widespread and abundant. Populations remain stable even when they are being hunted for fur, affected by disease, or a target for large predator populations because muskrats have the ability to reproduce quickly.

US Federal List: no special status

CITES: no special status

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

Population

Population Trend

Major Threats

Conservation Actions

Muskrats not only eat the grain on a farm but they have also been known to plug the drain tiles on farms as well. Muskrats also have a habit of building their homes around dikes. These homes make the dikes weak and eventually destroy the structure (Baker, 1983).

Negative Impacts: crop pest

The fur of a muskrat is important in the fur industry. Also, the meat from a muskrat is suitable for human consumption (Baker, 1983).

Positive Impacts: body parts are source of valuable material

Comments: Large numbers harvested for pelt.

Species Impact: Predation by muskrat appears to be inhibiting the recovery of endangered mussel species, and probably is placing some demes of endangered pigtoe mussel species in further jeopardy of extirpation from sites in upper Tennessee River drainage (Neves and Odom 1989).