Keeping fit on the ark: assessing the suitability of captive-bred animals for release

Reintroduction programs are widespread but have low success rates, particularly when captive-bred animals are used. There are high financial costs, and important ethical concerns about animal welfare. We have explored the concept of utilizing a behavioural approach to assess the suitability of captive-bred animals for release. We compared the behaviours of wild-bred and captive-bred animals in identical novel environments, using bank voles, Clethrionomys glareolus, as a model. The wild animals provided an adaptive baseline against which the behaviour of captive-bred individuals was compared. Although captive-bred voles displayed some wild-type behaviours - nest building and burrowing - despite lacking previous opportunities to do so, they were unable to utilize a key food resource and were less dominant. We suggest that a similar approach could be applied to species of conservation concern in order to rank available animals in terms of likely suitability for release. It could also help to identify characteristics that appear deficient in captive-bred animals, or to evaluate the impact of interventions such as environmental enrichment.