Food unpredictability in early life increases survival of captive grey partridges (Perdix perdix) after release into the wild

Reintroducing locally extinct species is an increasingly used conservation tool. However, many reintroductions fail to establish self-sustaining populations. The quality of the individuals released may crucially affect reintroduction success, but it is largely unknown which quality traits are important and how they might be improved, especially in captive-reared animals. We aimed at increasing survival of captive-bred grey partridges (Perdix perdix) after release. We experimentally tested the effects of prenatal and postnatal unpredictable food supply on post-release survival of two captive strains (two or >30 generations in captivity). 691 Full-grown birds representing all eight strain × prenatal × postnatal treatment combinations were released in autumn in 28 social groups (coveys) and followed in the field for six months by radio tracking and visual observations. Data were analysed with multistate capture-recapture models including several random effects. Post-release survival was higher in birds having encountered postnatal unpredictable food supply and decreased drastically with later release dates. Also, coveys strongly affected an individual’s survival prospects. Our results suggest that post-release survival of captive-bred grey partridges can be increased significantly through simple, inexpensive pre-release measures in captivity, i.e. exposing them to an unpredictable environment. Similar measures might be successful in other species and could ultimately enhance reintroduction success.