The growing presence of invasive species such as mink, nutria and squirrel represent a risk for the biodiversity of the Old Continent and for human health. The alarm was raised by a group of international researchers from Italy, Austria and Portugal
The growing presence in Europe of invasive species such as mink, nutria and squirrel represent a risk for the biodiversity of the Old Continent and for human health. The alarm was raised by a group of international researchers from Italy, Austria and Portugal in the research “Introduction, spread, and impacts of invasive alien mammals in Europe”, published in Mammal Review.
The presence of these species, intentionally introduced into territories other than their natural habitat as “pets or fur animals” or accidentally, has negative consequences not only on the environment but also on the potential transmission of pathogens, including zoonotic ones that can be transmitted from animals to humans. The research team highlighted that this risk is associated with 81% of the invasive alien species studied.
The work, coordinated by researchers from the Department of Biology and Biotechnology Charles Darwin of Sapienza and the University of Vienna, in collaboration with the University of Lisbon, highlighted how, despite the implementation of specific international agreements, reports of invasive alien mammals are on the rise at the expense of native species. The research consists of a systematic review of the literature published so far on 16 invasive alien species, supplemented with updated information and extracted from global databases.
ANDcco the most common invasive species in Europe
In order to tackle the phenomenon, the European Union adopted Regulation no. 1143/2014 with the aim of controlling or eradicating priority invasive alien species and preventing further introductions and settlements. The heart of the regulation is the Union List, a list of species towards which prevention, management, early detection and rapid eradication measures can be directed. Despite the community interest in the problem, no studies so far had specifically addressed the ecology of the invasive alien mammals on the list.
According to the authors of the Review, the most common invasive species in Europe are the raccoon dog (Nyctereutes procyonoides) native to eastern Siberia, the muskrat (Ondatra zibethicus), the mink (Neovison vison) and the raccoon (Procyon lotor), the latter of North American origin, which have invaded at least 19 countries and have been present in Europe for 90 years. The wide distribution of these mammals can be attributed to several factors, including adaptability, ability to colonize different environments and great reproductive capacity.
It has also been seen how all five species of Sciuridae (the family of rodents which includes, among others, marmots, gliders and tree squirrels) have been introduced in Europe at least once as “pets” or for entertainment: they are often illegally released in urban parks when you are no longer willing to keep them, or for ornamental purposes, although this activity, thanks to awareness campaigns, is falling into disuse.
Some infectious diseases associated with invasive mammals can threaten human health
Other species such as the nutria (Myocastor coypus), the raccoon or the American mink have, on the other hand, been repeatedly introduced to be bred as fur animals: the frequent, not always accidental and repeated escapes from farms over the years, have allowed established real populations in nature. “Although in the last 50 years there has been a decrease in the new introductions of alien mammals – explains Lisa Tedeschi della Sapienza, first author of the study – they continue to expand their ranges in Europe, aided by the illegal release of individuals in the wild, seriously threatening native biodiversity “.
Another important aspect concerns the involvement of the studied species in the transmission cycles of zoonotic pathogens: some infectious diseases associated with invasive mammals (such as echinococcosis, toxoplasmosis and bailisascariasis) can threaten human health. Just think of the Sars-CoV-2 virus outbreaks recorded in American mink farms in the Netherlands and Denmark in 2020, although the epidemiological role of mink (and other invasive mammals) in the virus cycle is still unclear.
Moreover, the American mink also exerts a negative effect through predation on other species, such as the Eurasian vole (Arvicola amphibius). Even the genetic heritage of native species can be threatened by invasive mammals, through hybridization (i.e. crossing between different animal species): in the United Kingdom, for example, the sika deer (Cervus nippon) is putting integrity at risk. genetics of the Scottish subspecies of red deer (Cervus elaphus scoticus).
‘Invasive mammals may contribute to the extinction of native species’
“Invasive mammals can contribute to the extinction of native species through various mechanisms, including competition, predation and transmission of diseases – declares Carlo Rondinini della Sapienza, coordinator of the work together with Franz Essl of the University of Vienna – The Eurasian red squirrel ( Sciurus vulgaris), for example, in Italy it became extinct in more than half of its range and was replaced by the eastern gray squirrel (Sciurus carolinensis), while the American mink colonized the area occupied by the European mink (Mustela lutreola), confining this native species, as well as in serious danger of extinction, in a few areas of Spain “.
Since the eradication of alien mammals that have such a wide distribution is difficult to achieve, it would be advisable instead to optimally manage the populations of the species that have become invasive and that could be problematic. “In this context – concludes Lisa Tedeschi – the identification of problematic populations or areas more invaded than others can help mitigate future impacts”.