Ondatra zibethicus (muskrat)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Habitat List
- Biology and Ecology
- Latitude/Altitude Ranges
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Ondatra zibethicus L., 1766
Preferred Common Name
Other Scientific Names
- Castor zibethicus
- Fiber zibethicus
- Mus zibethicus
- Myocastor zibethicus
- Ondatra americana Tiedemann, 1808
- Ondatra zibethica
International Common Names
- English: marsh hare; marsh rabbit; musquash; swamp rabbit
Local Common Names
- Denmark: Bisamrotte
- Estonia: ondatra; piisamrott
- Finland: piisami
- Germany: Biberratte; Bisam; Bisambiber; Bisamratte; Moschusratte; Muschmaus; Sumpfhase; Sumpfkaninchen; Wasserratte; Zibethratte; Zibetmaus; Zwergbiber
- Iceland: moskusrotta
- Latvia: bizamžurka; ondatra
- Lithuania: ondatra
- Poland: pizmak
- Russian Federation: ondatra
Summary of InvasivenessTop of page
Ondatra zibethicus is an amphibious rodent which is native to North America but has been introduced for its fur to much of Europe, as well as parts of Asia and South America. It inhabits wetlands, where it damages vegetation (for food and for building its lodges), banks and other structures (by burrowing), and neighbouring crops, and can threaten populations of a variety of native species. It is recommended for eradication by the Bern Convention on the Preservation of European Wild Plants and Animals and their Natural Habitats (Bern Convention Standing Committee, 1999), and is listed by DAISIE as one of the 100 worst invasive species in Europe (DAISIE, 2011), but its high rate of reproduction makes it difficult to control.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Mammalia
- Order: Rodentia
- Family: Muridae
- Subfamily: Microtinae
- Genus: Ondatra
- Species: Ondatra zibethicus
Notes on Taxonomy and NomenclatureTop of page
No subspecies or populations are described for Europe, although Errington (1961) considered the existence of 16 ‘forms’.
The order is characterized by a single pair of upper incisors and two groups of two pairs of teats. The genus Ondatra is close to Microtus and it can be suggested that this genus is derived from Microtus.
DescriptionTop of page
O. zibethicus is an amphibious rodent with a broad head and short ears. Its fur is of variable colour from grey to brown on the back, while the lower parts are lighter coloured. The fur is dense and waterproof resulting in a high degree of buoyancy. The tail is scaled, nearly nude and laterally flattened; it helps the animal to swim and fight. Well adapted to a semi-aquatic life, O. zibethicus can close its nose, ears, and mouth, so as to swim easily under water. When swimming, the body emerges from water and the tail acts as a rudder. Both sexes have perineal musk glands, the reason for the common name of the species. Males have a penial bone.
Total length: 46-67 cm (tail: 20-27 cm); weight: 0.6-2 kg.
The droppings have an elongated form, and are brown or black. They are usually deposited in a pile. They measure 10-12 mm in length with a diameter of 4-5 mm. Tracks through vegetation are about 10 cm wide.
DistributionTop of page
The natural range of O. zibethicus is throughout most of the United States and Canada, and in parts of northern Mexico (Long, 2003). The species has been introduced to Europe, parts of northern, central and eastern Asia, and Tierra del Fuego.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Argentina||Localised||Introduced||Anderson et al., 2006|
|Austria||Widespread||Introduced||1914||Invasive||Niethammer and Krapp, 1982; NOBANIS, 2011|
|Belgium||Widespread||Introduced||1925||Invasive||Niethammer and Krapp, 1982|
|Czechoslovakia (former)||Widespread||Introduced||1905||Invasive||Niethammer and Krapp, 1982|
|Denmark||Localised||Introduced||Birnbaum, 2006; NOBANIS, 2011|
|Estonia||Present||Introduced||1947||Birnbaum, 2006; NOBANIS, 2011|
|France||Widespread||Introduced||1928||Invasive||Niethammer and Krapp, 1982|
|Germany||Widespread||Introduced||1914||Invasive||Niethammer and Krapp, 1982|
|Hungary||Widespread||Introduced||1915||Niethammer and Krapp, 1982|
|Latvia||Localised||Introduced||1961||Not invasive||Birnbaum, 2006; NOBANIS, 2011|
|Lithuania||Localised||Introduced||1954||NOBANIS, 2011||Potentially invasive|
|Netherlands||Widespread||Introduced||1968||Invasive||Doude van Troostwijk, 1978|
|Norway||Present, few occurrences||Introduced||1969||Invasive||Danell, 1996|
|Poland||Widespread||Introduced||1924||Institute and of Nature Conservation, Polish Academy of Sciences, 2012||Originally invasive; now declining but still found throughout country.|
|Romania||Present||Introduced||1942||Niethammer and Krapp, 1982|
|Russian Federation||Present||Introduced||1928||Invasive||Danell, 1996|
|Yugoslavia (former)||Present||Introduced||1932||Invasive||Niethammer and Krapp, 1982|
History of Introduction and SpreadTop of page
O. zibethicus was first introduced to Europe in 1905 near Prague (Niethammer and Krapp, 1982). As early as 1906, different European countries tried to limit its expansion because there was no natural obstacle to its expansion. Deliberate introductions are reported from Finland (1920), Russia (1927) and Lithuania, Bulgaria in 1956 (Peshev, 1996), from Japan and Mongolia (Long, 2003), and also from France, Belgium and Poland.
HabitatTop of page
O. zibethicus lives mostly in freshwater, along riverbanks with slow moving waters, and in lakes, ponds, and wetlands. In northern countries it needs a water depth of between 1 and 2 m to prevent the water freezing completely and to allow vegetation growth.
Habitat ListTop of page
|Terrestrial ‑ Natural / Semi-natural||Riverbanks||Principal habitat||Harmful (pest or invasive)|
|Wetlands||Principal habitat||Harmful (pest or invasive)|
|Coastal areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Irrigation channels||Principal habitat||Harmful (pest or invasive)|
|Reservoirs||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Natural|
|Ponds||Principal habitat||Harmful (pest or invasive)|
|Estuaries||Secondary/tolerated habitat||Harmful (pest or invasive)|
Biology and EcologyTop of page
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
|D - Continental/Microthermal climate||Tolerated||Continental/Microthermal climate (Average temp. of coldest month < 0°C, mean warmest month > 10°C)|
|Df - Continental climate, wet all year||Preferred||Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)|
|Ds - Continental climate with dry summer||Tolerated||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
|Dw - Continental climate with dry winter||Tolerated||Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Bubo bubo||Predator||Adults/Juveniles||not specific|
|Canis latrans||Predator||Adults/Juveniles||not specific|
|Canis lupus||Predator||All Stages||not specific|
|Circus aeruginosus||Predator||Adults/Juveniles||not specific|
|Lutra lutra||Predator||Adults/Juveniles||not specific|
|Lynx lynx||Predator||Adults/Juveniles||not specific|
|Martes foina||Predator||Adults/Juveniles||not specific|
|Mustela putorius||Predator||Adults/Juveniles||not specific|
|Neovison vison||Predator||Adults/Juveniles||not specific|
|Procyon lotor||Predator||Adults/Juveniles||not specific|
|Vulpes vulpes||Predator||Adults/Juveniles||not specific|
Notes on Natural EnemiesTop of page
Predation by the Red Fox Vulpes vulpes occurs in lodges situated in shallow water close to the shore (Hjältén, 1991). Otters frequently feed on O. zibethicus during winter in Sweden (Skarén, 1993). Other predators are, in Europe, the Stone Marten Martes foina and the Polecat Mustela putorius, and in North America, American Mink Mustela vison, Fox Vulpes vulpes, Wolf Canis lupus, Coyote Canis latrans, Raccoon Procyon lotor, and Lynx Lynx lynx (Danell, 1996). In Northern European countries where the American Mink is widespread (for example in Poland), O. zibethicus seems to be declining (Brzezinski et al., 2010). Cases of predation on young individuals are also reported for the Eagle Owl Bubo bubo and Marsh Harrier Circus aeruginosus (Saunders, 1988; Link, 2005).
Means of Movement and DispersalTop of page
Young animals may have to find new territories. Movements are noticed during the autumn (varying according to the geographical location from August to November). Another movement occurs at the beginning of spring when individuals are searching for new territories. Movements are very dependent on the population density and on food resources. Precipitation can act as a favourable factor as flooded ground can facilitate movement. When they disperse, some animals can be seen trying to cross estuaries and cases of drowning have been reported.
Pathway CausesTop of page
Impact SummaryTop of page
Economic ImpactTop of page
O. zibethicus can dig galleries in the banks of rivers, ponds and sewage plants. The banks are weakened by this and can break, causing flooding. Burrows have been reported as a threat to the security of dikes in The Netherlands (research cited by Kadlec et al., 2007), and they also create difficulties for vehicles travelling on the dikes.
Environmental ImpactTop of page
Impact on habitats
O. zibethicus increases potential net nitrogen mineralization and nitrification rates. Their disturbance activities influence abiotic conditions, including soil nitrogen dynamics, which is an important component of wetland function (Connors et al. 2000). They alter invertebrate communities in wetlands, which affects food resources for wildlife and fish that feed on aquatic invertebrates in these habitats (De Szalay and Cassidy 2001).
An overabundance of O. zibethicus can modify the vegetal landscape (Kadlec et al., 2007). According to Burghause (1988), one animal is capable of cropping 1.5 m2 per night. When consuming rhizomatic plants, they can decrease biodiversity; as consumed species decrease and non-consumed ones (e.g. Carex) increase, the composition of the vegetation changes and reed beds can decline. Bernhardt and Schröpfer (1992) have shown that in the Ems region (Germany) O. zibethicus removes bulrushes (Typha latifolia), promoting the development of club-rushes (Scirpus lacustris). In such situations, insect communities and aquatic invertebrates could diminish because the opening up of reed beds could increase the possibilities for birds to feed, (see also Chashchukhin, 1987; Nummi et al. 2006; Danell 1996); this could be considered both as a negative and a positive effect.
Kadlec et al. (2007) reviewed literature on the effects of O. zibethicus on wetlands, with an emphasis on wetlands used for water treatment. O. zibethicus consume a small portion of the annual net primary productivity of the ecosystem, primarily rhizomes, but their mounds (lodges and feeding platforms) represent a significant share of this production (around 20%). Densities of 20 or more animals per hectare can destroy the majority of the macrophyte standing crop in a given year. Destruction of the wetland vegetative infrastructure may result in loss of some water quality parameters, but may not harm others. The integrity of berms may be threatened by burrowing. Impacts on wetland hydraulics are also possible. Loss of the emergent vegetation is viewed with dismay by owners and managers of treatment wetlands, regulators and the general public. Several case histories are reviewed by Kadlec et al. (2007) to illustrate the breadth and severity of muskrat damage in treatment wetlands. O. zibethicus control is given scant attention in existing treatment wetland literature, which provides very limited information on potential O. zibethicus problems, or the means to control them.
In Russia, there has been a reduction in edible plants and intensive growth of inedible plants which has been reported to cause a decrease in the number of O. zibethicus (Sokolov and Lavrov, 1993).
Impact on biodiversity
Abundance or more precisely overabundance of O. zibethicus can strongly threaten endemic species such as the Desman (Desmana moschata). It also impacts fishes and ground-nesting birds. Indirectly, through control operations, it could jeopardize populations of species such as the water vole Arvicola sapidus or even the otter Lutra lutra.
As well as crustaceans (such as crayfish), insects and bivalves such as zebra mussels (Dreissena polymorpha)(cf. Ulbrich, 1930; research cited in Danell, 1996), O. zibethicus sometimes feeds on threatened bivalve taxa such as Anodonta, Unio, and the freshwater pearl mussel Margaritifera margaritifera (cf. Brander, 1955, in Neves et al., 1989; Baumann and Everding 1986; Hochwald 1990; Zimmermann et al. 2000). This indirectly affects rare fish species that deposit their eggs in bivalves, such as the bitterling (Rhodeus amarus).
Seven trematode, three nematode, two cestode, one acanthocephalan, one protozoan, and three acarine species were recovered from 171 O. zibethicus taken in Manitoba, Canada. The fluke Quinqueserialis quinqueserialis was the most abundant. found in 93% of animals examined and with up to 1856 worms per host. Young muskrats were parasitized shortly after weaning, with the most prevalent parasites being acquired first. Capillaria michiganensis and Hymenolepis sp. were significantly more prevalent in female muskrats than in males (McKenzie and Welch, 1979).
O. zibethicus serves as an intermediate host for the cestode Echinococcus multilocularis. Infection rates can be up to 28% in wild populations (Genovesi, 2006); other reports range from 0.1 % (Borgsteede et al., 2003) to 11.18% (Hanosset et al., 2008).
In a study in Washington State and Idaho, USA, Campylobacter jejuni was recovered from 47.5% of O. zibethicus faecal samples, and Giardia spp. were detected in 82.5%. These findings indicate that O. zibethicus may be of importance to the health both of humans and of domestic animals (Pacha et al., 1985; Bitto and Aldras, 2009). In recent years several waterborne outbreaks of human diarrhoeal disease have occurred in various rural and mountainous areas of the United States. Some of these have occurred among recreationists frequenting high mountain areas, while others have been associated with municipal water systems. Giardia duodenalis has been implicated as the causative agent in many of these outbreaks, but in some instances Campylobacter jejuni has been reported as the responsible agent.
Petri et al. (1997) found that O. zibethicus could be a source of contamination of surface waters with oocysts of Cryptosporidium.
It appears to be susceptible to plague through subcutaneous infection by blood-feeding parasites and from feeding on the organs of animals which have died of plague (Anon., 1940).
Large multilobular pseudocysts characteristic of Toxoplasma microti have been found in the brains of O. zibethicus (Karstad, 1963). The species can also harbour leptospires (the cause of Weil’s disease in humans), hantaviruses, Borrelia (where ticks are abundant; this organism causes Lyme disease), liver flukes, and Francisella tularensis (the cause of tularemia) (Steiner et al., 1992; Moll van Charante et al., 1998; Feldman, 2003).
Social ImpactTop of page
Human injuries and deaths are reported due to accidents when burrows collapse under tractors or other agricultural machinery.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Highly mobile locally
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Has high reproductive potential
- Altered trophic level
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Infrastructure damage
- Modification of hydrology
- Modification of natural benthic communities
- Modification of nutrient regime
- Modification of successional patterns
- Negatively impacts agriculture
- Negatively impacts human health
- Negatively impacts animal health
- Negatively impacts livelihoods
- Negatively impacts aquaculture/fisheries
- Reduced amenity values
- Pest and disease transmission
- Difficult/costly to control
UsesTop of page
Uses ListTop of page
- Research model
Similarities to Other Species/ConditionsTop of page
The Coypu Myocastor coypus is also an invasive species in Europe. It was introduced sooner than O. zibethicus in most European countries but has disappeared from Scandinavia and, like O. zibethicus, was exterminated in the British Isles. A native of South America, it is less resistant to low temperatures, which constitutes a limit to its current expansion. However, climate change could benefit it. The biology and feeding habits of the two species are different enough for signs of their presence to be distinguished.
Prevention and ControlTop of page
Gaps in Knowledge/Research NeedsTop of page
As eradication is not possible, it is urgently necessary to develop measures of O. zibethicus control, based on single site analysis. In some cases, O. zibethicus can play a positive role in some sites and it could be more detrimental than useful to try to eliminate too many animals. Studies of population dynamics and feeding habits are still necessary.
ReferencesTop of page
Anderson C; Rozzi R; Torres-Mura JC; Sherriff MF; Schuttler E; Rosemond AD, 2006. Exotic vertebrate fauna in the remote and pristine sub-Antarctic Cape Horn Archipelago, Chile. Biodiversity and Conservation, 15:3295-3313.
Bern Convention Standing Committee, 1999. Recommendation No. 77 (1999) on the eradication of non-native terrestrial vertebrates. Recommendation No. 77 (1999) on the eradication of non-native terrestrial vertebrates. unpaginated. https://wcd.coe.int/ViewDoc.jsp?id=1489673
Bernhardt KG; Schröpfer R, 1992. [English title not available]. (Einfluss des Bisams auf die Vegetation. Untersuchungen im Ersatzbiotop Geeste im Emsland.) Naturschutz und Landschaftsplanung, 24:20-26.
Birnbaum C, 2006. NOBANIS - invasive alien species fact sheet - Ondatra zibethicus. NOBANIS - invasive alien species fact sheet - Ondatra zibethicus. North European and Baltic Network on Invasive Alien Species - NOBANIS, unpaginated. http://www.nobanis.org
Brzezinski M; Romanowski J; Zmihorski M; Karpowicz K, 2010. Muskrat (Ondatra zibethicus) decline after the expansion of American mink (Neovison vison) in Poland. European Journal of Wildlife Research, 56(3):341-348. http://www.springerlink.com/content/h45663p378554105/
Burghause F, 1988. The muskrat - from fur animal to pest. (Der Bisam - vom Pelztier zum Schädling.) "Einwanderer" - Zur Geschichte und Biologie eingeschleppter und eingewanderter Arten in Rheinland-Pfalz. I: Säugetiere (=Mainzer Naturwissenschaftliches Archiv, Beiheft 10) [ed. by Naturhistorisches Museum Mainz]. 27-37.
Burghause F, 1996. [English title not available]. (40 Jahre Bisam in Rheinland-Pfalz. Die Bedeutung eines eingewanderten Nagers und die Bemühungen, seinen Schaden einzudämmen.) Mainzer Naturwiss Archiv, 34:119-138.
Connors LM; Kiviat E; Groffman PM; Ostfeld RS, 2000. Muskrat (Ondatra zibethicus) disturbance to vegetation and potential net nitrogen mineralization and nitrification rates in a freshwater tidal marsh. American Midland Naturalist, 143(1):53-63.
Doude van Troostwijk WJ, 1978. Muskrat control in the Netherlands. In: Vertebrate Pest Conference Proceedings collection: Proceedings of the 8th Vertebrate Pest Conference, University of Nebraska, Lincoln, Nebraska, USA. 114-117.
Giban J, 1974. Use of Chlorophacinone in the struggle against the common Vole Microtus arvalis, Pallas, and against the Muskrat Ondatra zibethica L. In: Proceedings of the 6th Vertebrate Pest Conference, University of Nebraska - Lincoln. 262-271.
Hanosset R; Saegerman C; Adant S; Massart L; Losson B, 2008. Echinococcus multilocularis in Belgium: prevalence in red foxes (Vulpes vulpes) and in different species of potential intermediate hosts. Veterinary Parasitology, 151(2/4):212-217. http://www.sciencedirect.com/science/journal/03044017
Heidecke D; Seide P, 1986. Muskrat Ondatra zibethicus (L.). (Bisamratte Ondatra zibethicus (L.).) In: Buch der Hege [ed. by Stubbe, H.]. 640-666.
Hochwald S, 1990. Bestandsgefährdung seltener Muschelarten durch den Bisam (Ondatra zibethica). (Bestandsgefährdung seltener Muschelarten durch den Bisam (Ondatra zibethica).) Schriftenr. Bayer. Landesamt für Umweltschutz, 97:113-114.
Institute of Nature Conservation; Polish Academy of Sciences, 2012. Alien Species in Poland. Kraków, Poland. Institute of Nature Conservation, Polish Academy of Sciences. http://www.iop.krakow.pl/ias/Baza.aspx
Jokela J; Mutikainen P, 1995. Effect of size-dependent muskrat (Ondatra zibethica) predation on the spatial distribution of a freshwater clam, Anodonta piscinalis Nilsson (Unionidae, Bivalvia). Candian Journal of Zoology, 73:1085-1094.
Kadlec RH; Pries J; Mustard H, 2007. Muskrats (Ondatra zibethicus) in treatment wetlands. Ecological Engineering, 29(2):143-153. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VFB-4MJJC3W-1&_user=10&_coverDate=02%2F01%2F2007&_rdoc=4&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%236006%232007%23999709997%23640835%23FLA%23display%23Volume)&_cdi=6006&_sort=d&_docanchor=&view=c&_ct=11&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ff54cb27d69327ec3bc751291cb15785
McDonald B, 2006. Distribution, abundance, and habitat affinities of Oklahoma muskrats (Ondatra zibethicus): new insight from trapper reports. Proceedings of the Oklahoma Academy of Sciences, 86:39-45.
Moll van Charante AW; Groen J; Mulder PGH; Rijpkema SGT; Osterhaus ADME, 1998. Occupational risks of zoonotic infections in Dutch forestry workers and muskrat catchers. European Journal of Epidemiology, 14(2):109-116; 27 ref.
Reinhardt F; Herle M; Bastiansen F; Streit B, 2003. Economic impact of the spread of alien species in Germany. Federal Environmental Agency, Research Report: 201 86 211 UBA-FB 000441e. Germany: Federal Environmental Agency.
Sokolov VE; Lavrov NP, 1993. The muskrat: Morphology, Systematics, Ecology. Moscow, Russia: Nauka Publishers, 542 pp.
Zimmermann U; Gorlach J; Ansteeg O; Bossneck U, 2000. [English title not available]. (Bestandsstützungsmassnahme für die Bachmuschel (Unio crassus ) in der Milz (Landkreis Hildburghausen).) Landschaftspflege und Naturschutz in Thüringen, 37:11-16.
ContributorsTop of page
25/09/09 Original text by:
Patrick Triplet, Syndicat Mixte Baie de Somme Place de l'Amiral Courbet, 80 1000 Abbeville, France
Distribution MapsTop of page
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