Myocastor coypus | Coypu



Conservation status

Least Concern

Legal status

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].

Native status


First reported in the wild



Invasive species - risk of High Impact

Irish status

Present in the wild

Introduction pathways - 1

Escape from Confinement

Invasive score


NAPRA Ireland risk assessed

No. A full detailed risk assessment of this species to Ireland has not been undertaken.  

In the Great Britain risk assessment, which was used/adapted to support Union regulation listing of this species, the overall conclusion of the is HIGH with a HIGH level of confidence. See: 

The conclusion states: 'The species is already established in many countries and it is spreading in Europe. A large number of scientific publications demonstrate the invasiveness of the species in aquatic ecosystems and its economic impact due to damage to crops and river banks.' 

Species Biology


Coypu is a large, herbivorous, semi-aquatic rodent native to South America. It can weigh 5-9kg and is about 1m in head to tail length. It has dark fur often with lighter ends and has a white muzzle, a long cylindrical tail and small ears.

Distinctive features include large bright orange-yellow incisor (front) teeth that are usually visible, and webbed hind feet.


Largely herbivorous though may occasionally feed on mussels (Bertolino, 2009), coypu impact negatively on aquatic vegetation, including rare and threatened species and can remove Rumex spp and Nuphar lutea over large areas (Bertolino, 2009; Prigioni et al., 2005). Coypu are thought to impact on aquatic birds by decreasing nest habitat through consumption of vegetation and may prey on the eggs (Bertolino, 2009) and though egg predation has not been confirmed, coypu use aquatic nests as resting places and caused nest failure of 10-20% in Eurasian coots at sites in Italy (Bertolino et al., 2011). 

Its impact on human activities is primarily through the damage caused to river banks by burrowing, and though it is considered a pest of agriculture areas the costs in Italy from 1995-2000 of these activities were €10m and €935,138 respectively (Bertolino, 2009). Various studies would suggest the damage to crops can be mitigated by the presence of natural aquatic vegetation, as coypu forage on aquatic plants to avoid predation (Colares et al., 2010; D'Adamo, 2000; Guichón et al., 2003).

Coypu have also been shown to be carries of a number of diseases of importance of humans and domestic animals, including leptospirosis (Bertolino, 2009),  Fasciola hepatica (Menard et al., 2001), Giardia spp (Dunlap & Thies, 2002) and Toxoplasma gondii (Nardoni et al., 2011).


Inland surface water, Mire, bogs and fen


Sexual maturity 3-10 months. Gestation 127-138 days. Prenatal embryo losses are common during cold winter and in females in poor health condition. (Woods et al. 1992; GISD, 2017). Producing up to 3 litters of 4-6 pups a year (Bertolino, 2009; Guichon et al., 2003).

Pathway and vector description

Origin or reason for introduction of Irish individuals unknown. Previous spread globally has been through escapes or releases from fur farms (Bertolino, 2009).

Mechanism of impact

Disease transmission, Grazing/Herbivory/Browsing

Management approach

There is currently an EU wide ban on the sale of this species and personal and zoo ownership is being phased out (European Commission, 2017).

Live trapping

The use of live baited cage traps on floating rafts was highly effective in the UK eradication programme. Live trapping has the advantage of being able to release non-target species unharmed. Traps should be checked daily and target captures should be euthanised (Gosling & Baker, 1989) by shooting or with cloroform (Panzacchi et al., 2007).


Shooting can be effective when animals are forced out in the open during cold weather. The species is most active at night so 'lamping' may be most effective (leBlanc, 1994).


Poisoned bait is used in the Unites States and France. However, non-target species may also be killed. The animal often dies in the nest or elsewhere and consideration needs to be given to possible harm to the environment and other wildlife.

Broad environment


Habitat description

Freshwater habitats including rivers, lakes, ponds and drainage ditches (Bertolino, 2009).

Species group


Native region

South America

Similar species

It may be confused with Muskrat but as adults, Coypu is much larger. See:  Muskrat (Ondatra zibethicus)


World distribution(GBIF)

Naturalised in North America, Europe, central and eastern Asia, Japan, east Africa and the Middle East (Bertolino, 2009).

Previously present in Britain but eradicated after an 11 year removal campaign (Baker, 2006).

Irish distribution

Present in the wild -under eradication.

Since the first verified sighting near Killarney, Co. Kerry in 2010, Coypu have been seen and reported from seven separate locations (up to May 15th, 2017).  Just one animal was seen for six of the area sightings with two of the animals successfully removed and taken into captivity.

However one sighting in September 2016 was of at least 4 Coypu in the Curaheen River, Cork City.  A rapid response to survey and remove the animals in the area was initiated on 03/10/2016 with 10 animals removed by 03/11/2016. 

This sighting was the first formal Early Detection and Rapid Response alerts issued under the European Regulation on Invasive Alien Species [No. 1147/2014].

On May 7th 2017, a single Coypu was photographed swimming in the River Lee, Cork City about 4 kilometres from the Curaheen sightings. Efforts to ascertain extent of Coypu in Cork City area have been extended by encouraging citizen surveillance and reporting of all suspected sightings.

Native distribution

Native to South America in the area around Patagonia in Argentina from there it has spread into Brazil and Chile.

Temporal change

Date of first record category


Fifty year date category


Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre:

Further information information for this species in Ireland has not been published yet.  

In the DAISIE factsheet on the species Bertolino notes the following on control;

'Shooting is effective for population control when environmental conditions force the animals into the open, while cage trapping has also been used in the English eradication program.  In some countries like France and United States, baits with toxicants are used. North Americans use zinc phosphide on carrots or sweet potatoes.' See: DAISIE Factsheet

For a detailed review of the Coypu eradication scheme in Britain see: Baker, S., (2006). The eradication of coypus (Myocastor coypus) from Britain: the elements required for a successful campaign. In: Assessment and Control of Biological Invasion Risks. Shoukadoh Book Sellers, Kyoto, Japan and IUCN, Gland, Switzerland, pp.142-147.

Detailed review of this species is available in: Carter, J. & Leonard, B. (2002) A Review of the Literature on the Worldwide Distribution, Spread of, and Efforts to Eradicate the Coypu (Myocastor coypus). Wildlife Society Bulletin, Vol. 30, No. 1, pp. 162-175. 

Listed by the the Invasive Species Specialist Group (ISSG) of the SSC- Species Survival Commission of the IUCN -International Union for Conservation of Nature as one of the 100 Worst Invaders. Delivering Alien Invasive Species In Europe (DAISIE) project list the coypu as one of the 100 Worst Invaders in Europe.



Colares, I.G., Oliveira, R.N., Liveira, R.M. and Colares, E.P., 2010. Feeding habits of coypu (Myocastor coypus Molina 1978) in the wetlands of the Southern region of Brazil. Anais da Academia Brasileira de Ciências, 82(3), pp.671-678. 

D'Adamo, P., Guichon, M.L., Bó, R.F. and Cassini, M.H., 2000. Habitat use by coypu Myocastor coypus in agro-systems of the Argentinean Pampas. Acta Theriologica, 45(1), pp.25-34. 

Dunlap, B.G. and Thies, M.L., 2002. Giardia in beaver (Castor canadensis) and nutria (Myocastor coypus) from east Texas. Journal of Parasitology, 88(6), pp.1254-1258.

European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg. 

Global Invasive Species Database (2017) Species profile: Myocastor coypus. Available online: [Accessed: 27/07/2017]

Gosling, L.M. & Baker, .SJ. 1989. The eradication of muskrats and coypus from Britain. Biological Journal of the Linnean Society,38: 39-51. Site accessed 3 October 2107. 

Guichón, M.L., Benitez, V.B., Abba, A., Borgnia, M. and Cassini, M.H., 2003. Foraging behaviour of coypus Myocastor coypus: why do coypus consume aquatic plants?. Acta Oecologica, 24(5), pp.241-246.

LeBlanc D.J. 1994. Prevention and control of wildlife damage – Nutria. USDA – APHIS, Animal Damage Control. Site accessed 3 October 2017.

Ménard, A., Agoulon, A., L'Hostis, M., Rondelaud, D., Collard, S. and Chauvin, A., 2001. Myocastor coypus as a reservoir host of Fasciola hepatica in France. Veterinary Research, 32(5), pp.499-508.

Panzacchi, M., Bertolino, S., Cocchi, R. & Genovesi, P. 2007. Population control of coypu Myocastor coypus in Italy compared to eradication in UK: a cost-benefit analysis. - Wildlife Biology 13: 159-171. Site accessed 3 October 2017. 

Woods, C.A., Contreras, L., Willner-Chapman, G. and Whidden, H.P. 1992. Myocastor coypus. Mammalian Species 398: 1-8.

IUCN Red List of Threatened Species

CABI Datasheet

Global Invasive Species Database

DAISIE Factsheet

Additional comments

Coypu are also occasionally refered to as "Nutria".