In many places the problematic exotic species have already gained a foothold, but how will the raccoon and raccoon dog populations develop further? Researchers report that there are many other ways of spreading for invasive petty robbers in Europe. They recorded the areas in which similar climatic conditions prevail as in the home regions of the two animal species and thus determined their potential for spreading. As the scientists emphasize, raccoons and raccoon dogs not only threaten biodiversity: Both can also transmit diseases to animals and humans. The raccoon dog is even considered a possible carrier of corona viruses.
The world is changing – this also applies to the composition of species: Humans have transported many animal and plant species from one place to another through their global activities. In some cases, the strangers ended up in paradise: They were able to multiply strongly due to the lack of competitors or enemies as well as abundant food sources and thus advanced to become invasive species. Two famous examples are the North American raccoon (Procyon lotor) and the raccoon dog, originally from East Asia (Nyctereutes procyonoides). The two visually similar, but only distantly related representatives of the canine species (Caniformia) were introduced to Europe as fur and hunting animals in the course of the 20th century. In freedom they found good living conditions and were thus able to multiply and spread. Raccoons are now found in 20 European countries and raccoon dogs in 33 countries.
Possible living spaces explored
“Raccoons and raccoon dogs are flexible when it comes to their habitat and food. In addition, they hardly have any natural enemies in Europe. It is assumed that their spread is therefore only limited by the climate, ”says Judith Kochmann from the Senckenberg Biodiversity and Climate Research Center at the Goethe University in Frankfurt. In order to sound out the corresponding potential for spreading in Europe, she and her colleagues used eight variables to analyze the temperature and precipitation conditions under which raccoons and raccoon dogs live in their home regions in North America and East Asia. So they could determine the demands of both species. They then investigated which areas of Europe offer conditions that fall within the tolerance range of the two immigrants and thus offer opportunities for them to spread.
It turned out that large parts of Europe are suitable as living spaces. “There is still a lot of room for improvement,” says Kochmann. “It is therefore likely that the range of the raccoon and raccoon dog in Europe will probably increase considerably,” says the scientist. In detail goes from the Maps to the appropriate areas : Many regions offer raccoon and raccoon dogs equally potential for spreading and could thus become new habitats for both species. However, a slightly different spreading pattern can also be expected. Because the raccoon apparently copes a little better with cold peaks and the raccoon more with warmth. According to this, the “American” could conquer more habitats in the south, while the East Asian immigrants could spread even further into Scandinavia and Eastern Europe.
Ecosystem vandals and disease carriers
As the researchers emphasize, the two petty predators could not only threaten biodiversity in their new habitats, but also become a health risk. Because they are known as possible carriers of pathogens such as parasites and viruses, some of which can also affect humans – keyword zoonoses. “We are currently researching which pathogens are carried by species in Europe in our joint project ZOWIAC ‘Zoonotic and Wildlife Ecological Effects of Invasive Carnivores’”, says co-author Sven Klimpel from Goethe University Frankfurt.
It is already known: “Raccoons transmit the raccoon roundworm and are considered reservoir hosts for the West Nile virus. Raccoon dogs harbor similar pathogens, including lyssaviruses, which cause rabies, canine distemper viruses and the fox tapeworm, ”says Klimpel. However, the parasitologist particularly emphasizes a special risk: “Raccoon dogs are currently suspected of acting as reservoir hosts for coronaviruses – such as SARS-CoV-2,” said Klimpel.
Against this background, the modeling of the potential distribution areas can now also be important for epidemiological considerations, say the scientists. In addition, the results can be used to plan management measures to control raccoon and raccoon dog populations in Europe. Even if they have apparently already firmly established themselves, the furry fellows may at least be kept in check with them.
Source: Senckenberg Research Institute and Nature Museums, specialist article: Mammal Review, doi: 10.1111 / mam.12249