GaiaZOO European Hamster (Cricetus cricetus) Breeding Program: enclosure setup to determine if the hamsters are ready to mate. This is necessary because the wild population cannot survive on its own at the moment. Every year a new breeding schedule is drawn up to determine which hamsters can mate with whom so as to maximize genetic diversity and minimize kinship. Every year over the course of the summer, European hamsters from the breeding program are released in the various habitats. GaiaZOO, Kerkade,The Netherlands, May.