Top Ten: Invasive Animals in Germany

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Invasive alien species can displace native species, cause health problems and inflict economic damage. According to a report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), invasive species (neozoans) are a major cause of 60% of all extinctions. Human activities in particular cause non-native species to enter areas where they did not previously occur, either intentionally or unintentionally. Climate change also facilitates the spread of species.

For Germany, the Federal Agency for Nature Conservation (BfN) currently provides an EU list of invasive alien animal and plant species that includes 47 animal species.

Twenty-five of these species have been recorded in the wild in Germany.

• Spiny-cheek crayfish (Faxonius limosus)
• Marbled crayfish (Procambarus virginalis)
• Signal crayfish (Pacifastacus leniusculus)
• Red swamp crayfish (Procambarus clarkii)
• Chinese mitten crab (Eriocheir sinensis)
• Yellow-legged hornet (Vespa velutina nigrithorax)
• American bullfrog (Lithobates catesbeianus)
• Raccoon (Procyon lotor)
• Nutria (Myocastor coypus)
• Muskrat (Ondatra zibethicus)
• Raccoon dog (Nyctereutes procyonoides)
• Common kingsnake (Lampropeltis getula)
• Black bullhead (Ameiurus melas)
• Eastern mosquitofish (Gambusia holbrooki)
• Pumpkinseed (Lepomis gibbosus)
• Reeves’s muntjac (Muntiacus reevesi)
• South American coati (Nasua nasua)
• Ruddy duck (Oxyura jamaicensis)
• Chinese sleeper (Perccottus glenii)
• Topmouth gudgeon (Pseudorasbora parva)
• Eastern gray squirrel (Sciurus carolinensis)
• Siberian chipmunk (Eutamias sibiricus)
• Pond slider (Trachemys scripta)
• African sacred ibis (Threskiornis aethiopicus)
• Egyptian goose (Alopochen aegyptiaca)
• Common myna (Acridotheres tristis)

Not all alien species are considered invasive. Invasive species spread in a non-native area and have a negative impact on the ecosystem, for example by displacing native species or spreading diseases. It is not yet known whether the Nosferatu spider (Zoropsis spinimana), which originates in the Mediterranean region, should be regarded as an invasive animal species in Germany. It remains to be seen whether it will have a negative impact on native fauna.

These invasive species cause the most damage

The following list shows the top ten invasive alien animals in Germany that have spread the most and are often believed to have the most negative impact on the ecosystem:

Raccoon

Raccoons (Procyon lotor) were originally imported from North America in the 1920s and 1930s for fur production and kept on fur farms. In 1934, two pairs were deliberately released in Hesse to establish a population there. Today, raccoons can be found almost everywhere in Germany.

These adaptable members of the raccoon family are omnivores and actively hunt prey such as amphibians, reptiles, bats and fish, as well as eggs and young birds in particular. They are also widespread in urban areas, where they often rummage through garbage cans. Heavy predation by raccoons adds to existing threats to native species and may jeopardize their long-term survival.

The raccoon is now subject to hunting laws in all German federal states and is hunted as a means of population control. In most states, it may be hunted throughout the year, although hunting seasons and closed seasons vary regionally. At the same time, some argue that the raccoon has by now become part of Germany’s native fauna.

Signal crayfish / Red swamp crayfish

The freshwater signal crayfish (Pacifastacus leniusculus), which originates in North America, was deliberately introduced to Europe from 1960 onward to revive crayfish fisheries after native noble crayfish populations had declined. However, it brought with it a new and particularly infectious strain of the pathogen that causes crayfish plague and infects native European crayfish. Crayfish plague is incurable and fatal to infected animals.

The signal crayfish is not the only crayfish introduced from America; the red swamp crayfish (Procambarus clarkii) is also a carrier of the disease. Today, invasive crayfish species are widespread in almost every European country and threaten native crayfish.

The crayfish Pacifastacus nigrescens, endemic to California, became extinct around 1900 after signal crayfish and red swamp crayfish entered its habitat along with the crayfish plague pathogen. The Ash Meadows killifish also disappeared in 1948 because the red swamp crayfish competed with it for food and habitat.

Spinycheek crayfish

Around 1890, a Prussian chamberlain first introduced the spinycheek crayfish (Faxonius limosus) to Europe, particularly to the Oder river system, importing around 90 animals of unknown North American origin on a trial basis. The species found ideal conditions and quickly spread across northern and western Germany. Its spread was often aided by deliberate stocking intended to establish it as a fishery substitute for the noble crayfish (Astacus astacus).

Today, the spinycheek crayfish is widespread in Western and Central Europe and is the region’s most common crayfish species. It is a proven carrier of crayfish plague, to which it is itself immune.

Egyptian goose

The Egyptian goose (Alopochen aegyptiaca) has been kept as an ornamental bird in Europe since the 18th century and spread to Central Europe in recent decades. Originally native to Africa, it can now be found throughout Germany in urban parks and at recreational lakes. These waterfowl are said to compete with native bird species for nesting sites and territories. They are also said to be highly aggressive near their nests, driving away other waterbirds or even endangering their broods. Egyptian goose droppings are considered a potential health hazard, which is one reason the species was placed on the EU list of invasive species.

Ecological damage caused by Egyptian geese has not yet been demonstrated, so population management aimed at reducing their numbers is difficult to justify. Nevertheless, hunting Egyptian geese is currently permitted in nine federal states. Around 10,000 were killed in Germany during the 2021/2022 hunting season.

Nutria

The nutria (Myocastor coypus), also known as the coypu, originates in South America and was bred for fur in Germany from the 1920s onward. After animals escaped from fur farms, they became established in the wild. Today, they can be found throughout Germany, especially along rivers and around lakes and ponds.

Although nutrias are almost entirely herbivorous, they still cause damage. They feed on crops and undermine dikes and other hydraulic structures. The rodents also cause extensive feeding damage to mussels and to submerged and bankside vegetation, potentially destroying habitats of rare species. Their population in Germany doubled between 2006 and 2016 alone because nutrias can reproduce throughout the year. They are not subject to hunting law in Germany, but special permits issued to reduce their numbers resulted in around 95,000 nutrias being killed during the 2021/2022 hunting season.

Common raccoon dog

Originally native to eastern Siberia, Japan and northern China, raccoon dogs (Nyctereutes procyonoides) were introduced to the western regions of the former USSR for their fur. From there, they spread westward and were first recorded in West Germany in the 1960s.

Their spread in Germany is viewed critically because this alien species has no natural predators in its new environment and may have a negative impact on the ecosystem. There are concerns that predation on eggs and young birds in meadows, along riverbanks and coasts, and in burrows could displace native bird species. Predation on reptiles and amphibians is also considered a potential threat to native wildlife.

So far, however, there is no conclusive scientific evidence that the raccoon dog’s spread directly threatens the population of any particular animal species. Nevertheless, the raccoon dog has been subject to hunting law since 1996 and may be shot.

Common muskrat

The muskrat (Ondatra zibethicus), which is actually a member of the vole family, was brought from Alaska to Bohemia by Prince Joseph Colloredo-Mansfeld in 1905 and introduced to Europe from there. It spread rapidly along rivers and streams, colonized large parts of Europe and reached Germany in 1914.

The muskrat occupies niches no longer filled by native species in Central Europe and causes damage through its burrowing, particularly in river and coastal areas. It eats bankside and aquatic plants, which can alter the structure of riparian ecosystems and impair the habitat of some bird species. It also occasionally preys on animals such as crayfish and amphibians. Muskrats are also said to threaten mussel populations already under pressure from pollution. Finally, the rodents act as intermediate hosts for the fox tapeworm.

Muskrats are not subject to hunting law, but special permits allow several thousand animals to be killed or trapped each year.

Stone moroko

The stone moroko (Pseudorasbora parva), a fish in the carp family, was probably introduced unintentionally from Asia to Romania in the 1960s and has since spread across Europe. The species was first recorded in Germany in 1984 and has since become particularly widespread in the south of the country.

Its adaptability, rapid reproduction and small size give the stone moroko enormous potential to spread. Its presence poses several threats to native wildlife. It can threaten other species by competing for food and habitat, thereby contributing to a loss of species diversity in bodies of water. Its heavy predation on zooplankton, invertebrates and fish spawn also threatens native fauna.

Pond slider

The pond slider (Trachemys scripta) probably reached Germany from North America through the exotic pet trade. Large numbers were imported into the European Union as pets during the 1980s and 1990s. Red-eared and yellow-bellied sliders are popular with aquaterrarium keepers, but many owners released them when they became too large or difficult to care for.

The turtles may threaten native species such as the European pond turtle by competing for food and habitat. Experiments have shown that European pond turtles (Emys orbicularis) kept with pond sliders suffered weight loss and high mortality. As omnivores, pond sliders may also have a negative impact on other parts of the ecosystem, including amphibians, fish and aquatic plants. They are known to prey heavily on amphibian larvae.

What to do about invasive species?

There are various measures in place to curb the spread of invasive alien species. There has been a legally binding regulation on dealing with invasive species at EU level since 2015, which restricts the trade, transport and release of certain species and requires the monitoring and prevention of their spread.

In Berlin, for example, specific measures are being taken to minimize the impact of invasive species on ecosystems. These include trapping and removing invasive crayfish from bodies of water, as well as providing advice on preventing raccoons from entering homes and gardens.

Education and awareness are important: people should understand how to deal with alien species. Animals such as raccoons, nutrias and Egyptian geese should not be fed. Garden waste should not be dumped in the wild, where it may unintentionally provide food for them.

Stricter regulation of trade in potentially invasive animals could help protect native wildlife. The German Animal Welfare Association advocates coexisting with alien species already established in Germany instead of hunting them. It argues that hunting invasive species is unlikely to succeed because new animals would quickly recolonize the area. Neutering animals and replacing eggs with dummy eggs would be more sustainable. It is also important to monitor the spread of established alien species closely so that preventive action can be taken quickly when necessary.

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