Can subadult captive-bred common hamsters (Cricetus cricetus) reproduce in the wild? New perspectives for restocking programs

International audienceIndividual recruitment is a critical component of conservation biology. While most restocking programs seek to increase population growth, they often encounter challenges in identifying the factors that could maximize post-release survival and reproduction, largely due to the difficulties in conducting tests on vulnerable species. Regarding the Critically Endangered common hamster (Cricetus cricetus), restocking programs generally rely on the release of one-year-old captive-bred individuals. However, these hamsters face high mortality rates in the weeks following their release. Because young individuals display higher behavioural plasticity, they might adapt faster and thus be optimal candidates for restocking programs. However, the release of animals which are too young to reproduce may jeopardize the success of restocking programs. We investigated the reproductive success of 1.5- and 3-month-old females (referred to as “subadult” denoting months-old hamsters after weaning and before their first hibernation) captive-bred common hamsters after release. Field data (camera traps and trapping sessions) and genetic analysis enabled us to determine parentage of pups born in the wild. Our experiment showed that 3-month-old and 1.5-month-old females reproduced successfully after the release at the same time than one-year-old hamsters.Both groups produced their first litter approximately 30 days post-release given an estimated mating date of 10 days post-release. These findings indicate that released captive-bred hamsters reach sexual maturity around 47 days after birth. The release of subadult individuals could provide advantages to improve the success of restocking programs. However, more studies are needed to compare the survival and reproduction rates of months-old hamsters and older individuals to assess their overall role in population recruitment in comparison to older individuals usually released