This stamp from the stamp series ‘Estonian fauna’ depicts the Siberian flying squirrel (Pteromys volans L.), a rare species, the European habitats of which are limited to Finland, Estonia, Belarus, and Russia. The flying squirrel has a flap of skin on both sides of its body, with which it can glide up to several dozen metres from tree to tree. This elusive animal, mainly active at dusk and night, is rarely seen. In summer, it feeds on tree leaves, and in winter, on the buds and catkins of birches, alders, and aspens. They reproduce once or twice a year, with 2 to 4 young in a litter. The flying squirrel is mainly endangered by the reduction and fragmentation of old mixed forests with old hollow aspens that are suitable for habitats. A critically endangered species in Estonia, it can nowadays only be found in North-East Estonia. The flying squirrel is included in the list of priority species in the European Union’s Nature Directive and the list of category I protected species in Estonia.