Dormouse - A

 Fauna – Dormouse

Edible or fat dormouse (Glis glis)

The European edible (or fat) dormouse is a nocturnal rodent and excellent climber that spends most of its active time in treetops. During the day it sleeps in the karst underground, in tree hollows or in the nesting boxes of birds. It hibernates in winter (in the karst underground or in tunnels beneath the roots of large trees). Dormice in Slovenia begin hibernating with the first frost and wake up in April. During hibernation they lose between 35% and 50% of their bodyweight. They mainly feed on fruits and seeds, occasionally also eating fungi and animal food (including insects and small vertebrates). They are known to gnaw bark. In the conditions prevailing in Slovenia, the success of hibernation is probably dependent on the amount of fruit produced by oak, beech and hornbeam trees. A plentiful supply of acorns, beechnuts and hornbeam nuts allow dormice to build up a sufficient quantity of subcutaneous fat. They do not store food. Female dormice have one litter a year but the birthing period lasts the whole summer. The lifespan of the edible dormouse is up to five years. Young animals not yet sexually active form the bulk of the population.

The coast is the lowest-lying area in which the edible dormouse is found, while in the mountains it is thought to live up to the beech forest treeline. Its preferred habitat consists of deciduous and mixed forest on karst. It can be very common in the Limestone Alps, the Dinaric Alps, the pre-Alpine and pre-Dinaric hills and in sub-Mediterranean Slovenia. It frequently enters human habitations. These are usually buildings on the edge of a forest, although dormice also come to the outskirts of larger towns.

They are prey to numerous carnivores; from members of the marten, fox and jackal families to wild cats and, occasionally, large carnivores such as the Eurasian lynx. Beech marten can even hunt them and prey on them in their winter refuges, but their biggest predators are probably owls. In the Dinaric forests of the Dolenjska, Kočevje and Notranjska regions, this mainly means the Ural owl. In the Slovenian part of the Istrian peninsula, the dormouse is among the most important species in the diet of the Eurasian eagle-owl and is also a not insignificant part of the diet of the tawny owl. The density of the dormouse population in the Dinaric fir and beech forests of Slovenia fluctuates considerably, with numbers being exceptionally high in individual years – so-called dormouse years. One of the causes of such anomalies is undoubtedly an abundant crop of fruit from the main forest tree species such as beech, oak and hornbeam, which in Slovenia occurs every two to seven years and is reflected in a high dormouse birthrate and low mortality during hibernation. The Dinaric forests are the only part of the world where people hunted dormice for food and fur (because of their periodic abundance) and they are an important part of local tradition, particularly in Notranjska and Kočevje.Evidence of dormouse hunting dates back to ancient Roman times, although the first documentary mention in our part of the world is from the year 1240. Detailed accounts are also found in Valvasor’s famous work The Glory of the Duchy of Carniola (1689).

Hubert Potočnik

Department of Biology, Biotechnical Faculty, University of Ljubljana