Hazel dormice are difficult to find, as they are no bigger than a thumb and live mostly in dense undergrowth. Its secretive life style means that there is hardly anything known about this small mammal. The Wienerwald BR and its project partners, the Forschungsinstitut für Wildtierkunde und Ökologie and the Austrian Federal Forestry Authority (ÖBf AG) jointly initiated an extraordinary species conservation project for the hazel dormouse. With the assistance of local inhabitants, foremost among them children and adolescents, it was possible to establish where the hazel dormouse occurs in the Wienerwald and to what extent it is endangered. Hazelnuts with characteristic tooth marks provided telltale signs of the presence of these rodents. Children and adolescents were invited to take part in the quest.