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The Dransdorf creek: Nutria population spreading across Bonn

The Dransdorf creek : Nutria population spreading across Bonn

Nutrias, the large semiaquatic rodents also called coypus are breeding and expanding their habitats across Germany. This is true also in Bonn and the region. Authorities warn it could become a problem.

The nutria is a favorite amongst visitors at the Rheinaue. Recently, the semiaquatic rodents were spotted at the Dransdorfer creek. The Lower Nature Conservation Authority has observed a growing population in Bonn. The Biostation is warning about the invasive species and advising that the nutria population needs to be kept under control.

"There were five of them that I saw here every day in the creek," reports a resident who lives on Hans-Sachs-Strasse. The nutrias stayed there until mid-April. Then they disappeared overnight and were never seen again.

The city administration confirms that the animals live along the stream. Exact figures are not available, says Isabel Klotz from the city press office. A count is to take place at the end of the year in the city area. The fact that the animals have been sighted at the Dransdorf creek does not surprise Christian Chmela. "Nutrias are extremely adaptable and have been spreading in the Rhineland for decades," says the head of the Bonn/Rhein-Erft Biological Station. It is foreseeable that the species will soon end up in all local waters, says the biologist. "The animals migrate from the Rhine up the streams."

Nutrias are especially at home in the lake at the Rheinaue park

One of the oldest habitats for the nutrias is said to be the mouth of the Sieg River. "The animals have been there since the 1980’s," Chmela recalls. "At that time, around 40 nutrias were counted there. In the meantime, the large semiaquatic rodents have also appeared in many other places in Bonn, reports the Lower Nature Conservation Authority. "For example, in Graurheindorf and in the city center," says Mira Landgraf. So far, the main area has been at the lake in the Rheinaue park, she says. "Due to the growing awareness of the animals and the increased feeding of them, as well as the very mild winters in the recent past, the population there has not only maintained itself, but has grown," reports Landgraf. For those reasons, one can assume that the species will spread to other bodies of water in Bonn.

This scenario is nearly a reality in the Rhine-Erft district, says Chmela. There, nutrias are said to live in almost every stream. "For example, we have found nutrias in dried-up ditches in Zülpich," the director reports. "This shows me that the animals have a certain resilience and resolutely take over any habitat that is suitable for them." The nutrias like it best at the water's edge. "They need an embankment where they can build their burrows," Chmela explains. Streams and lakes with large plant vegetation are particularly suitable, he says.

Nutrias endanger flora and fauna

"The nutria feeds primarily on aquatic as well as marsh plants. They also eat large mussels, some of which are also under protection," explains Landgraf. The Lower Nature Conservation Authority and the Biostation see a particular threat to native flora and fauna here. "We observe at various water bodies that the reed zones are disappearing," Chmela warns. Species-rich aquatic vegetation with lake and pond roses become completely destroyed by the nutria. "In some cases, this endangers protected habitats and the animal species that depend on them, such as waterfowl," says Landgraf.

In the Netherlands, nutria populations have been heavily targeted for this reason. "Now the Dutch have the problem that more and more nutrias are coming from Germany," says Chmela. The animal is now considered an invasive species “needing to be kept under control" not only there. "As cute as the animal is, they cause significant damage to the native ecosystem. We are forced to take action," Chmela emphasizes. The biologist cites two examples as the reason: "At the Krickenbecker Lakes near the Dutch border, our colleagues wondered why certain bird and plant species were declining there." With the help of cameras, the Biostation working on site was able to pinpoint the nutrias as the sole cause. On the Lower Rhine, in the district of Kleve, the animals are also said to have massively encroached on nature reserves. "There is now an EU-funded project there, which aims to reintroduce reeds," says Chmela.

A ban on feeding nutrias has been in force in Bonn since 2019. However, there is no population control through hunting, according to the Lower Nature Conservation Authority. "Since the nutrias enjoy great popularity among the population, strong opposition would have to be expected if the measure were implemented," says Landgraf. So the goal cannot be to remove all nutrias from Bonn, but to limit the existing population to an acceptable level, they say. "With stronger enforcement of the feeding ban and more public education," Landgraf says. "You just have to consider: Where do nutrias endanger the habitats of animal and plant species and where not?" says Chmela. Flood protection is also an issue here, he says, because the animals can make dikes and embankments unstable when they dig their burrows.

(Orig. text: Niklas Schröder / Translation: Carol Kloeppel)