Behavioural trait assessment as a release criterion: boldness predicts early death in a reintroduction programme of captive‐bred swift fox ( Vulpes velox )

Abstract Reintroduction of captive‐bred animals is a key approach in conservation attempts for many endangered species, however, post‐release survival is often low. Rearing conditions may be unlike those encountered upon release and the animals may not have had experiences necessary for survival in the wild. Animals may also habituate in captivity to stimuli that may pose a danger after release and/or there may be selection for behavioural traits, in particular reduced fearfulness, that may not be suited for the wild. Here, variation in boldness was assessed in captive‐bred swift fox ( Vulpes velox ) and tested for influence on survival after release. Radio‐tracked individuals that died in the 6 months following release were those judged previously as bold. In the presence of novel stimuli in captivity, they had left their dens more quickly, approached more closely to the stimuli and shown more activities indicating low fear than did those that survived. These individuals were less suited for release. Future selection of release‐candidates on the basis of behavioural variation should enhance the success of reintroduction programmes.