The release of unwanted pets into the wild has facilitated the spread of non-native species around the world. One such example is the North American Trachemys scripta which is on the EU’s Invasive Alien Species of Union concern list, but regularly found in the wild.
Picture by James Dickey.

By James W. E. Dickey, Chunlong Liu, Elizabeta Briski, Christian Wolter, Simon Moesch, and Jonathan M. Jeschke.

Read the full paper here.

The spread of non-native species (NNS) – animals, plants and other organisms introduced outside their native range – is a major driver of biodiversity loss. An increasingly globalised world has facilitated new introduction pathways for NNS to spread, while also benefiting major vectors like the pet trade.

The freshwater pet trade is a major driver of species introductions, which can happen both intentionally and unintentionally. For example, a lack of opportunities to surrender unwanted pets can lead to owners releasing them into the wild. Pet owners can intentionally release their pets if they become unwanted for reasons of aggression, high rates of reproduction, size or a lack of time on the part of the owner. Unintentional releases include animals escaping from wholesalers, stores or owners, with escapes from garden ponds being a major problem. Management of established NNS is highly challenging and prevention is therefore most effective. However, prevention requires the identification of species most likely to be introduced and to establish in the new ecosystem.

To determine the freshwater species available in Germany and their associated risks, we surveyed: (1) physical pet stores and garden centres in the country’s largest city, Berlin; (2) German pet websites; and (3) eBay Kleinanzeigen, the country’s largest online marketplace. We had three key results. First, we revealed 669 species in the German trade, of which 651 were non-native. Twenty-two have already been found in the wild in Germany, with a number already on the list of “100 of the World’s Worst Invasive Alien Species” and the EU’s “Invasive Alien Species of Union Concern” list. Second, we found more available species to be cheaper; and such cheap, readily available species have previously been highlighted as having high risks of release. Third, we highlighted the riskiest species in the trade using our novel “Release Risk” metrics – a three-pronged risk assessment method that accounts for availability, price and the likelihood of species surviving the climate in their non-native range. We propose that this method can become an informative screening tool for species in the trade, and be used to inform legislation to limit future releases of NNS.