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Ondatra zibethicusmuskrat

By Toni Lynn Newell

Ge­o­graphic Range

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).

Habi­tat

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).

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Phys­i­cal De­scrip­tion

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).

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    680.0 to 1800.0 g
    23.96 to 63.44 oz
  • Average mass
    1135.8 g
    40.03 oz
  • Range length
    410.0 to 620.0 mm
    16.14 to 24.41 in
  • Average basal metabolic rate
    4.363 W
    AnAge

Lifes­pan/Longevity

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

Be­hav­ior

Muskrats are arranged in large fam­ily groups and live in def­i­nite ter­ri­to­ries. If the con­di­tions are over­crowded, the fe­males will kick their off­spring out of the group. Muskrats con­tinue to live in large grous even when fight­ing and can­ni­bal­ism occur in high rates. Muskrats are ac­tive at all times of the day but most ac­tive from mid-af­ter­noon until just after dusk. Muskrats are good swim­mers and can stay un­der­wa­ter for 12 - 17 min­utes. Muskrats, how­ever, move rel­a­tively slowly on land. Muskrats com­mu­ni­cate by musk, which also is used as a warn­ing for in­trud­ers. They are ca­pa­ble of vo­cal­iz­ing by squeaks and squeals. Muskrats have poorly de­vel­oped senses of sight, hear­ing, and smell. They are af­fected by quick changes in tem­per­a­ture, and dry, hot weather is es­pe­cially bad for them. Their homes and bur­rows pro­tect them from the el­e­ments. Muskrats also have a spe­cial adap­ta­tion called re­gional het­erother­mia, which reg­u­lates the flow of blood to the feet and tail, al­low­ing these struc­tures to be cooler than the body core (Baker, 1983).

Com­mu­ni­ca­tion and Per­cep­tion

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.

Food Habits

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).

Pre­da­tion

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.

Ecosys­tem Roles

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.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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

Con­ser­va­tion Sta­tus

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.

Con­trib­u­tors

Toni Lynn Newell (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

Ref­er­ences

Baker, R.H. 1983. Michi­gan Mam­mals. Michi­gan State Uni­ver­sity Press. United States of Amer­ica.

"An­i­mal Life His­to­ries Data­base" (On-line).

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Classification

Classification

  • Kingdom Animalia animals
  • Phylum Chordata chordates
  • Subphylum Vertebrata vertebrates
  • Class Mammalia mammals
  • Order Rodentia rodents
  • Family Cricetidae New World rats and mice, voles, hamsters, and relatives
  • Genus Ondatra muskrat
  • Species Ondatra zibethicus muskrat