The coypu: an intruder that swims with you

The unstoppable invader that colonizes the rice fields of Pals

The coypu (Myocastor coypus) is an invasive exotic species native to South America, introduced to the Empordà in 2004 and its numbers have grown exponentially. This semi-aquatic rodent has a significant negative impact on local ecosystems, particularly in aquatic and agricultural areas, where it affects crops such as rice, and the native vegetation. Since 2013, containment and control strategies have been implemented, but its eradication is difficult. This case exemplifies the global problem of invasive species, which threaten biodiversity and ecological balance.

Coipú. © Manfredrichter via Pixabay.

The coypu is a newcomer to our beaches! This exotic invasive species seems to have arrived with plans to stay. The first sighting of a coypu in the Empordà was in 2004 at a golf course in Pals, and since then, its population has grown exponentially.

The coypu is a rodent belonging to the family Myocastoridae, and it is the only surviving member of this family. Its appearance is like a mixture of rat, otter, and beaver. It can weigh up to 10 kilograms and grow longer than half a metre. It can be easily recognized by its large orange incisors and its hairless, scaly tail. It has long brown fur with a gray undercoat. Adapted to a semi-aquatic lifestyle, the coypu has webbed feet, perfect for swimming and diving, with eyes and nostrils positioned on top of its head, enabling it to see and breathe while swimming.

The coypu lives in areas with flowing or stagnant water that have abundant aquatic vegetation, as well as along riverbanks and coastal marshes. They dig shallow burrows close to the water, where they live in pairs or colonies. More active at night, coypus have a herbivorous diet mainly consisting of aquatic plants and riverside vegetation, along with roots, rhizomes, and wild and agricultural plants such as cereals and apples. It can also feed on bivalve mollusks. Their ability to adapt their diet is one reason they have managed to survive and thrive in different regions.

Coypus reproduce 2 or 3 times a year, giving birth to about 5-6 pups each time. These pups are capable of swimming while nursing, thanks to the lateral position of the mother's mammary glands. The young can reproduce within their first year and have a lifespan of about 4-6 years. So, do the maths! How many offspring can a female have over her lifetime?

In our region, coypus have few natural predators, only foxes and some birds of prey.


This mammal is native to South America, earning its name from the Mapuche word ‘kóypu’ (water trail), referring to its swimming style. The indigenous South Americans used to capture it for food and use its fur. It was introduced to various parts of Europe and other regions of the world through fur farms because of its value to the fur industry. The coypu's fur is dense and soft, making it highly prized for making coats and other fur items. The coypu's first entry into Europe, documented in the late 19th century, resulted from escapes or intentional releases from fur farms established on the continent, allowing them to live in the wild.

Therefore, the coypu is an invasive exotic species and is on the list of the 100 most harmful exotic invasive species in Europe, according to the International Union for Conservation of Nature and Natural Resources (IUCN). Since 2013, both in Catalonia and in Spain, it has been declared an invasive species (Royal Decree 630/2013, of August 2). The current Catalan population is thought to have originated from French colonized individuals, with a noticeable population surge noted since 2013-2014. Widely spread across Girona's northeast, they have migrated from l'Alt Empordà, colonizing river basins such as the Muga, Fluvià, and Ter rivers, stretching into the regions of Ripollès, Selva, Pla de l'Estany, Garrotxa, Gironès, and Baix Empordà. In certain stretches of the Fluvià or Muga rivers, you might even encounter up to a dozen coypus per kilometre.

What is the difference between an exotic species and an invasive species?

Exotic or non-native species are those that are introduced into an environment where they do not naturally occur.

Invasive species, on the other hand, are those exotic species that not only establish themselves but also spread rapidly in their new habitat, disrupting its natural balance and posing a threat to the native biodiversity.

For some years now, this mammal has threatened the ecological balance, especially of aquatic ecosystems and riverbanks areas. It also has a significant negative impact on agriculture, affecting different types of crops, especially rice cultivation. Their digging activity to build burrows or search for food can alter riverbanks and drainage canals, destabilizing banks, as well as affecting meadows and crops near water, and degrading irrigation systems.

When feeding, coypus only consume the underground stems and young shoots of plants, leaving the rest untouched. This leads to the destruction of a large quantity of aquatic vegetation, resulting in a decline in native plant species. One of the most affected plants has been the flowering rush, which is already endangered in the Empordà region, and is disappearing from Baix Ter’s rice fields. It also affects other animal species by reducing the surface area used by aquatic birds for nesting, as well as damaging fish spawning areas. Additionally, its rummaging through ground vegetation, though not for food, causes erosion along riverbanks, streams, and marshes.

Coypu showing its orange-colored incisors. INaturalist (CC-BY-NC).

Finally, we must not overlook the negative consequences for humans and other animals; as it can act as a host and/or vector for infectious and parasitic diseases such as leptospirosis, fasciolosis, hydatid disease, tuberculosis, or septicemia.

In response, the Department of Climate Action has produced a strategy, prioritizing efforts to contain and control coypu populations. This includes limiting their expansion towards southern basins and in other current habitats while reducing population densities to safeguard sensitive ecosystems.

Coipú. ©

The only effective method we have to combat the spread of this species and minimize its impact is through selective trapping or firearm use. These measures are implemented through capture and population control campaigns led by Rural Agents and other professionals.

The coypu has only been successfully eradicated from one location worldwide: Great Britain. Introduced to the islands in the early 20th century for its fur, coypus flourished, with populations reaching around 200,000 individuals. However, extensive eradication programs in the 1960s and 1970s, involving dedicated teams of professional trappers, successfully removed coypus from the wild by the late 1980s. This has led to the recovery of local wildlife and plant populations that were previously impacted by this invasive species. Ongoing monitoring efforts are now in place to prevent their reintroduction.

In other European countries, despite significant efforts in countries like France and Germany, eradication campaigns have not been successful. Eradication is much more complex than in the case of Great Britain, because we are not an island and the population density of the species quickly recovers due to immigration from adjacent areas.

A specimen of coypu captured in the province of Girona. © Gencat.

The coypu is a fascinating animal that has found its place in the aquatic habitats of the Empordà. However, it has not been welcomed here due to its impact on invaded ecosystems. We should not forget that we, as the ultimate invaders, are responsible for the introduction of coypus and other invasive species like the American mink. Like the coypu, the American mink arrived here via the fur trade, and they have swiftly become a menace to ecosystems and native species. According to EXOCAT, a comprehensive database of exotic and invasive species in Catalonia, there are approximately 1,700 exotic species, with about 200 (12%) being invasive. Smaller animals or plants can have an even greater impact on local ecosystems. Notably, the majority of intruders are plants, such as the notorious pampas grass, found on Pals beach and still in many private gardens as an ornamental plant. 

With climate change, we are accelerating the invasion process of species that can be harmful to biodiversity. Additionally, the areas most altered by human activity are more likely to attract species that do not encounter predators, whereas ecosystems with high biodiversity are less susceptible to biological invasions.

Globally, a recent UN study reveals that humans have introduced over 37,000 species of exotic animals and plants into various regions around the world, with more than 3,500 of these species classified as invasive. According to the IUCN, biological invasions rank as the second most significant cause of species extinction, following habitat destruction.

If you encounter a coypu, call the Rural Agents! 972 405 340

Data de creació de l’article: 7/3/2024.

Foto de capçalera: Coipú. © Shivainc via Pixabay.


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