Complete Name : Ondatra zibethicus, Linnaeus 1766
Taxonomy : Mammalia » Chordata » Mammalia » Rodentia » Muridae » Ondatra zibethicus
Authors : Piero Genovesi
Last Updated : October 31st, 2006

Muskrat.

Ondatra zibethica -

Large (410-620 mm; weight 680-1800 g), stocky aquatic rodent with large head, small eyes, very short rounded ears. Dark brown, with underside slightly paler in colour. Tail as long as the head and body (180-295 mm), hairless and flattened laterally. Common name refers to the musky odour. They eat almost any aquatic vegetation as well as crops. Also feed on crayfish, mussels, turtles, frogs and fish in ponds where vegetation is scarce.

• Dispersal Mechanisms
  • Young usually disperse after their first winter, when they are less than 1 year old. They have good dispersal ability along streams and water bodies. The average expansion speed in central Europe in the first half of last century was around 11.3 km per year, but high variance has been found at different latitudes, in some cases exceeding 20 km/yr.
• Reproduction
  • They have on average two or three litters per year (up to 5-6 in favourable climatic and habitat conditions) after a gestation period of 25-30 days. Able to swim by 2 weeks of age, weaned at 3-4 weeks when they begin to feed independently. Young become sexually mature the spring following birth.
• Known Predators/Herbivores
  • American mink (Mustela vison) and European mink (M. lutreola) kill muskrats to feed on them and also to take over their burrows. Otters (Lutra lutra), barn owls (Tyto alba) and harriers (Circus spp) also prey on muskrats. However, in general predation does not regulate muskrat populations.
• Resistant Stages (seeds, spores etc.)

• Native (EUNIS Code)
  • Inland surface water habitats, D: Mire, bog and fen habitats, F9: Riverine and fen scrubs
• Habitat Occupied in Invaded Range (EUNIS Code)
  • C: Inland surface water habitats, D: Mire, bog and fen habitats, F9: Riverine and fen scrubs
• Habitat Requirements
  • Live in both brackish and freshwater lakes, ponds, streams, rivers and marshes. They are well adapted to cold climates. However, they show higher reproductive rates in southern latitudes. Tidal fluctuations, periodic flooding or droughts limit species distribution. Dry summers and severe winters have detrimental effects.

Imported for fur farming in many countries, it has escaped into the wild or has been intentionally released with the aim of establishing populations to be harvested for their furs.

• Native Range
  • Broadly distributed all over North America except extreme northern parts.
• Known Introduced Range
  • Successfully introduced into most of the Palearctic, including Great Britain, northern and central Europe, Ukraine, Russia, parts of China and Mongolia, and Honshu Island in Japan. Also introduced in South America (Argentina and Chile). Successfully eradicated from Britain and Ireland in the thirties.
• Trend
  • Abundant in northern and central Europe, it is increasing and expanding in many countries. Still absent or localized in most southern European countries.

known distribution area (in CGRS grid squares; in countries; along coast)

	eradicated
	extinct
	not present; eradicated
	native distribution range in CGRS grid squares
	native range
	assumed native range
	infrequent distribution
	key distribution area
	not established

• Ecosystem Impact
  • Strongly affects vegetation dynamics through grazing. Threatens endemic species such as the desman (Desmana moschata). It also impacts shellfishes, fishes and ground nesting birds; endangered mussel populations are particularly impacted.
• Health and Social Impact
  • In some areas they carry Leptospira, which causes Weil’s disease in humans. It serves as an intermediate host for the cestode, Echinococcus multilocularis (infection rates up to 28% in wild populations). Burrowing can weaken riverbanks causing them to collapse. Can damage railroads and dams.
• Economic Impact
  • Cause extensive damage to crops, irrigation structures, railroads and dams. In some cases undermine fences or cause bogging of machinery. It has also a potential impact on aquaculture industry. In Germany it is estimated at € 12,4 mln/yr (€ 4.6 mln/yr for sanitary aspects, € 2.3 mln/yr for maintenance of waterways, € 1.9 mln/yr for impacts to hatcheries and fish breeders by damaging ponds and dams. Cost of eradication efforts in Germany estimated at over € 3 mln/yr.

• Prevention
  • Fencing is effective at preventing damage to valuable crops or gardens. Damage to pond dams can be prevented through stone rip-rapping of dams, or by constructing dams with proper slope and size. Also drawing of ponds in winter is used to remove muskrats. Frightening devices are seldom effective.
• Mechanical
  • Control usually by trapping, less frequently by shooting. Most effective capturing devices are stove-pipe traps and Conibear®-type traps (not allowed in Europe under the Council Regulation 3254/91). Control usually through live traps. Also snares and iron bow-nets placed in front of entrances of holes are used.
• Chemical
  • Zinc phosphide (63% concentrate) and anticoagulants are used to control muskrats. However, undesired impacts of toxicants on non-target species have been reported. Poison baits are usually placed on floating platforms to minimize risks to non-target species.
• Biological
  • None.

The following contributors have provided records in the DAISIE database for this species.

The following experts registered themselves as having knowledge about this species or its family.

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Danell K (1978) Population Dynamics of the Muskrat in a Shallow Swedish Lake. J Animal Ecology, 47(3):697-709

Nummi P, Väänänen VM, Malinen J (2006) Alien Grazing: Indirect Effects of Muskrats on Invertebrates. Biological Invasions, 8(5):993-999

Wilson D, Ruff S (1999) The Smithsonian Book of North American Mammals. Washington, Smithsonian Institution Press

Fournier-Chambrillon C, Berny P, Coiffier O, Barbedienne P, Dasse B, Delas G, Galineau H, Mazet A, Bonzenc P, Rosoux R, Fournier P (2004) Field evidence of secondary poisoning of free-ranging riparian mustelids by anticoagulant rodenticides in France : implications for the conservation of the european mink (Mustela lutreola). J Wildl Dis 40:688-695

Gosling LM, Baker SJ (1989) The eradication of the muskrats and coypus from Britain. Botanical Journal of the Linnean Society 38:39-51

Haydon DT, Stenseth NC, Boyce MS, Greenwood PE (2001) Phase coupling and synchrony in the spatiotemporal dynamics of muskrat and mink populations across Canada Proc.Natl. Acad. Sci. USA 98: 13149-13154

Miller JE (1972) Muskrat and beaver control. Proc. First Nat. Ext. Wildl. Workshop, Estes Park, Colorado, pp 35-37

Miller JE (1974) Muskrat control and damage prevention. Proc. Vertebr. Pest Conf. 6:85-90

Orueta JF (2003) Manual práctico para el manejo de vertebrados invasores en islas de España y Portugal. Gobierno de las Islas Baleares y Gobierno de Canarias, p 254 http://www.iucn.org/places/medoffice/invasive_species/docs/manual_practico.pdf

Sheail J (1988) The extermination of the muskrat (Ondatra zibethicus) in inter-war Britain. Archives of Natural History 15:155-170

Tuyttens FAM, Stuyck JJJM (2002) Effectiveness and efficiency of chlorophacinone poisoning for the control of muskrat (Ondathra zibethicus) populations. New Zealand Journal of Zoology 29:33-40

van den Bosch F, Hengeveld R, Metz JAJ (1992) Analysing the Velocity of Animal Range Expansion Journal of Biogeography 19(2):135-150

Warwick T (1940) A contribution to the ecology of the musk-rat (Ondatra zibethica) in the British Isles. Proceedings of the Zoological Society of London, Series A, 110:165-201