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

Abstract

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.

Appendix 1

Questions regarding the security of the enclosures against animal escape included in the data sheets used by the evaluators when assessing enclosure security (from Guillén-Salazar 2003). For the purpose of this study an enclosure was considered “secure” only when both conditions were simultaneously met. Otherwise the enclosure was categorized as “non-secure”.

Condition 1

The enclosure has a complete, well maintained, and appropriate physical barrier to prevent the escape of the animals housed within (including sewage lines, filtration systems and, in general, any opening or valve that could allow the escape of an animal or part of it such as eggs). Each of the following questions should be answered negatively to meet this condition.

• a. Could the barrier be knocked down by the animals held in the enclosure?

• b. Could the animals exit the enclosure by leaping or climbing the barrier (including the use of vegetation, tools, etc.)?

• c. Could the animals escape by digging under the barrier?

• d. Could the animals go through the barrier (especially young individuals)?

• e. Are there any pipes or ducts (sewage lines, water channels, etc.) in the enclosure that could allow the escape of the animals held in it?

• f. In the case of being a drive through or walk through enclosure, a double gate entry and exit system should be in place with sufficient space to allow the gates to be securely closed at the front and rear of any vehicle (or person) which may enter or need to enter the enclosure. Could the animals held inside exit the enclosure through any of the gates?

• g. Could the integrity of the barrier be compromised by any external factor (e.g. a fallen tree on the barrier)?

Condition 2

The public cannot release the animals held at the enclosure directly or indirectly. Each of the following questions should be answered negatively to meet this condition.

• a. Could the public capture the animals and remove them from the enclosure?

• b. Are there any doors or windows that could be opened by the public due to lack of continuous supervision by zoo personnel and/or because they are not properly locked?

• c. Are there any objects surrounding the enclosure such as rocks, branches or forgotten tools that could be used to free the animals held at the enclosure (e.g. by tearing down the fences comprising the physical barrier of the enclosure)? Note: Violations with premeditation, planning and preparation that could be considered as an offense are not considered.