The risk of zoological parks as potential pathways for the introduction of non-indigenous species

Zoological parks have been associated with an increasingly frequent origin for accidentally released animal species. Such species have become invasive in some cases. The goals of this study are to evaluate the risk of potential animal escape at zoological parks by assessing the security of animal enclosures, and to identify which factors could be affecting such security. We visited a random sample of 1,568 animal enclosures belonging to 63 Spanish zoological parks, and assessed their security with a defined criteria based on the suitability of the physical barrier of the enclosure and the impossibility for the public to release the animals. To our criteria, we found 221 enclosures which were non-secure against animal escape. Such enclosures were unevenly distributed among 47 zoological parks (74.60% of the sample), and housed non-indigenous species in 79.64% of the cases (21 species listed by the European Inventory of Invasive Species). Seven factors were analyzed to assess their effect on enclosure security. Six of them were found to have an effect, and three were selected by a logistic regression model as the main predictors for secure enclosures. Such factors are discussed, and measures are suggested to reduce the risk of zoological parks as a potential pathway for the introduction of non-indigenous species.