Ondatra zibethicus | Musk Rat | Muscfhrancach
Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).
Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [No. 1143/2014].
First reported in the wild
Invasive species - risk of High Impact
Present in the wild
Introduction pathways - 1
Escape from Confinement
Large, brown, stocky aquatic mammal, weighing up to 2kg, with a large head, short round ears, long hairless flattened tail (Genovesi, 2009).
Omnivorous they feed on a variety of aquatic and semi aquatic vegetation and crops, though they will feed on crayfish, mussels, frogs and fish, in areas where aquatic vegetation is scarce (Genovesi, 2009). The impact of muskrats on aquatic vegetation can lead to declines in waterfowl due to loss of nesting habitat, and on various prey species (particularly mussels) in areas where aquatic vegetation is lacking (Genovesi, 2009). The main impacts on economic activites is through burrowing damaging river and railway banks, dams and damage to crops, with annual costs in Germany estimated at €12.4 million (Genovesi, 2009).
There appears to be a strong negative correlation between the presence of the America mink (Neovison vison) and muskrat in Poland, with the number of sites inhabited by muskrats decreasing from 44-7% over a ten year period (Brzezinski et al., 2010). While a study of historic population trends between mink and muskrat in their native range revealed a 8-9 year predator prey cycle (Erb et al., 2001), this has not been observed in Europe to date (Brzezinski et al., 2010).
Inland surface water habitats, Mire, bogs and fen, Heath, scrubland and tundra
Sexually mature at 1 year of age, average of 2-3 litters per year of 5-6 pups (Genovesi, 2009).
Pathway and vector description
Muskrats have been widely introduced in Northern European countries particularly as the result of escapes from fur farms (Genovesi, 2009). Two separate introduction events for muskrat have occurred in Ireland . The first detailed by Fairley (1982), involved the introduction of 3 individuals at Annaghbeg House, near Nenagh, Co Tipperary in 1929 to attempt to establish a population for fur farming. Between 1933 and 1934, 487 muskrats were trapped and by 1935 the population had been eradicated.
In 2015 a muskrat was recorded in Cork but to date no details of how the species came to be introduced to Ireland are known.
Mechanism of impact
Competition, Predation, Grazing/Herbivory/Browsing
Eradication is only possible in the early stages of invasion (Gosling & Baker, 1989).
The main method of control is live trapping. However, it is only effective if it is carried out intensively. Baiting traps with carrots, celery or fruit and using floating platforms increases effectiveness. Once trapping stops, populations quickly recover (Triplet, 2009).
Shooting carried out at dawn and dusk when the species is most active can be attempted but it is generally ineffective and only small numbers are killed (Triplet, 2009).
Numbers may also be controlled by native predators including the red fox (Vulpes vulpes) and the polecat (Mustela putorius) (Triplet, 2009).
Muskrat density is related to habitat quality, as abundant muskrat populations dramatically reduce vegetation and vegetation may not have the potential to recover in poor habitats compared to areas where plants are abundant and rich with nutrients (Skyriene & Paulauskas, 2013). In Poland the most abundant muskrat populations are found in eutrophic waters in areas of intensive cultivation (Brzezi´nski et al., 2010).
Species is originally native to North America but has been introduced to South America. Europe and Asia (Genovesi, 2009).
Present in the Wild - No details of distribution or abundance of the species.
Native to North America from Alaska to northern Mexico (Genovesi, 2009).
Date of first record category
Fifty year date category
Records submitted to Data Centre in 2023
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How can you help
Report any sightings to the National Biodiversity Data Centre.
Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.
Brzezinski, M., Romanowski, J., Zmihorski, M. and Karpowicz, K., (2010). Muskrat (Ondatra zibethicus) decline after the expansion of American mink (Neovison vison) in Poland. European Journal of Wildlife Research, 56(3), pp.341-348.
Erb, J., Boyce, M.S. and Stenseth, N.C., (2001). Spatial variation in mink and muskrat interactions in Canada. Oikos, 93(3), pp.365-375.
Fairley, J.S., (1982). The muskrat in Ireland. The Irish Naturalists' Journal, pp.405-411.
Genovesi, P (2009) Ondatra zibethicus (Linnaeus), muskrat (Muridae, Mammalia). In: Handbook of Alien Species in Europe, Springer.
Gosling, LM & Baker, SJ (1989) The eradication of muskrats and coypus from Britain. Biological Journal of the Linnean Society,38: 39-51. https://www.researchgate.net/publication/227800788_The_eradication_of_muskrats_and_coypu_from_Britain Site accessed 3 October 2107.
Skyriene, G. and Paulauskas, A., (2013). Distribution of invasive muskrats (Ondatra zibethicus) and impact on ecosystem. Ekologija, 58(3).
Triplet, P (2009) Invasive Species Compendium Datasheet report for Ondatra zibethicus (muskrat) https://www.cabi.org/isc/ Site accessed 3 October 2017.
IUCN Red List of Threatened Species