Taxonomic name: Myocastor coypus (Molina, 1782)
Common names: Biberratte (German), coipù (Spanish), coypu, nutria (English), ragondin (French), ratão-do-banhado (Portuguese-Brazil), Sumpfbiber (German)
Organism type: mammal
Myocastor coypus (coypu) is a large semi-aquatic rodent which originated from South America. However, due to escapes and releases from fur farms there are now large feral populations in North America, Europe and Asia. Their burrows penetrate and damage river banks, dykes and irrigation facilities. Myocastor coypus' feeding methods lead to the destruction of large areas of reed swamp. Habitat loss caused by coypus impacts plant, insect, bird and fish species.
Myocastor coypus (coypu) is a large rodent (5-9kg; 40-60cm body; 30-45cm tail), superficially rat-like, pelage brown and yellow-brown in colour with a cylindrical tail. It has webbed hindfeet, with a footprint up to 15cm long, imprints of the web is often visible; incisors are prominent and bright orange-yellow (unlike rats which are yellow-brown), with white marks on muzzle (Woods et al. 1992, Carter and Leonard 2002). Faeces cylindrical, up to 70mm long, with fine longitudinal striations (LeBlanc, 1994).
coastland, lakes, riparian zones, water courses, wetlands
Myocastor coypus (coypu) are generally found near permanent water, particularly reed beds and swamp/marsh. Also found in rivers, streams, lakes, ponds and brackish marsh in coastal areas.
Myocastor coypus (coypu) burrows undermine the banks of rivers and dykes causing instability (Carter and Leonard, 2002). Feeding on rhizomes and young shoots of marsh plants leads to plant community breakdown and can lead to erosion in coastal habitats (LeBlanc, 1994). Coypu feeding on sea oat rhizomes in Mississippi barrier islands have led to sand dune erosion in these important habitats (GSMFC 2005).
At high densities coypu are able to convert marshland to open water by feeding on plants. Habitat destruction caused by coypu threatens rare marshland species of bird, fish and invertebrates. In Italy coypu have caused breeding whiskered tern (Chlidonias hybrida) to decline by largely destroying the cover of water-lilies Nymphaea in Valli di Argenta a designated IBA (Important Bird Area). The habitats of two national treasure species in Japan - a critically endangered dragon fly (see Libellula angelina in IUCN Red List of Threatened Species) and a fish the vulnerable deep-bodied bitterling (see Acheilognathus longipinnis in IUCN Red List of Threatened Species) (Shirow Tatsuzawa, pers. Comm.) are threatened by coypu.
Coypu also feed on agricultural crops (Carter and Leonard 2002) including sugarcane, alfalfa and root crops (Woods et al. 1992)
Myocastor coypus (coypu) are valued as a source of fur (Carter and Leonard 2002) and have been used as a meat source. Coypu provides prey for alligators and other native predators in some areas
Myocastor coypus (coypu) prefer habitats near the water, animals are rarely observed over 100m away from river. Severe winter could reduce reproductive success and adult survival.
Native range: Native to South America south of 23 degree latitude, including Argentina, Bolivia, southern Brazil, Chile, Paraguay, and Uruguay (Carter and Leonard 2002).
Known introduced range: Introduced to areas of North America, Europe, Africa and Asia (Carter, 2007).
Introduction pathways to new locations
Other: Fur farms, introduced for fur exploitation.
Local dispersal methods
Escape from confinement:
Natural dispersal (local):
Feral populations of coypu are managed by shooting and trapping. Eradication is preferable for small to medium size populations but some level of control is essential in most cases if eradication is not feasible . High fur prices can help encourage sufficient hunting to control populations (Carter and Leonard 2002). In times of high fur prices little damage was observed to wetlands in Louisiana, USA (Marx et al. 2003). In 2002 a bounty system existed in Louisiana. That year a $12.5 million investment resulted in 342 trappers returning 300,000 tails over a 4 month season. Animals were shot or trapped and carcasses were either retained and sold as pelts or disposed of in the wetlands (Marx et al. 2003). Coypu have been eradicated from a number of states in the USA and are classed as pests in countries throughout the world (Carter and Leonard, 2002). A population of around 6000 coypu (Genovesi, 2005) was eradicated from East Anglia, UK in a campaign using cage traps. 24 trappers were employed for 8 years at a cost of £2.5 million (Gosling, 1989). An eradication was proposed for a small lake in Sicily but opposition by the World Wildlife Fund (WWF) prevented the eradication taking place (Genovesi, 2005). An unsuccessful attempt was made to use pythons (Python rebae) as a biocontrol for coypu in Lake Navaisha in Keya (Harper et al. 1990)
Herbivorous, Myocastor coypus (coypu) eat wetland plants and crops. Selective feeding causes massive reduction in reed swamp. Occasional feeding on freshwater mussels are reported. It practices coprophagy. (Woods et al. 1992, Carter and Leonard 2002, Genesis Laboratories, Inc. 2002)
Placental. Sexual. Significant relationship between winter severity and female reproduction in the following spring. Prenatal embryo losses are high until 13-14 weeks of gestation. Sexual maturity 3-10 months. Gestation 127-138 days. Litter size 2-9; prenatal embryo losses are common during cold winter and in females in poor health condition. (Woods et al. 1992, Genesis Laboratories, Inc. 2002)
Myocastor coypus (coypu) breed throughout the year; post-partum oestrus. Sexual maturity 3-10 months. Gestation 127-138 days. Mean litter sizes 5-6 (2-9), prenatal embryo losses are common during cold winter and in females in poor health condition. Woods et al. 1992)
This species has been nominated as among 100 of the "World's Worst" invaders
Principal sources: Woods, C.A., Contreras, L., Willner-Chapman, G. and Whidden, H.P. 1992. Myocastor coypus. Mammalian Species 398: 1-8.,
Carter, J. and Leonard, B. 2002. A review of the literature on the worldwide distribution, spread of and efforts to eradicated the coypu (Myocastor coypus). Wildlife Society Bulletin 30: 162-175.
Compiled by: Dr. Sandro Bertolino, DIVAPRA Entomology and Zoology, University of Turin, Italy & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Sunday, 13 April 2008