From the breeding facility to the natural environment. How do European hamsters behave after being released?

In the European range of the critically endangered European hamster Cricetus cricetus, both in situ and ex situ conservation programmes are in place to breed these animals and to release captive-bred individuals into natural populations to enhance for their demographic and genetic diversity. The study analysed the behaviour of individuals following their release into the wild, as well as the importance of sex, age and origin for the frequency of behaviours crucial for survival in the wild. The hypothesis was also formulated that the timing of leaving the aviary was independent of an individual’s age, sex and origin. In 2020–2021, 115 hamsters were released into acclimatization aviaries and their behaviour was observed. Thirty-four behavioural categories were distinguished with the most frequent being vigilance (42 %) and exploration (30 %). Hamsters also exhibited behaviours characteristic of captive-raised animals (14 %). Differences in vigilance were found between individuals of different origins. More of these behaviours were exhibited by hamsters with at least one wild parent compared to those whose both parents from a captive background. The time taken to leave the aviary was not dependent on either the age or the sex. However, a highly significant relationship was found between the hamsters' origin and the time when they left the aviary. Juvenile females and males born of captive-born parents were the fastest to leave the aviary. Juvenile females of mixed parentage, adult males born of captive-born parents and adult males caught in the wild took the longest time to leave the reintroduction site. The data obtained are crucial for the conservation of this endangered species.