Reproductive biology of common dormouse (Muscardinus avellanarius) in a coastal evergreen scrub forest of Central Italy

The common dormouse (Muscardinus avellanarius) is a widespread European glirid species that occupies a variety of deciduous woodlands throughout the continent. His breeding behaviour has been investigated by several authors using nest boxes in various woodlands of northern Europe, while information from mediterranean habitats is very scarce. Previous studies in Italy suggested that, differently from northern populations, the activity pattern of coastal mediterranean populations is characterized by a regular winter activity, an autumnal breeding period, and a probable summer dormancy, related to climatic factors such as mild winters and dry summers. These marked differences in the activity pattern between temperate and mediterranean populations suggested a different reproductive biology. Therefore, the aim of this research was to study some basic reproduction parameters, i.e. the period and length of breeding season, the number of litter per year, the average litter-size and the first age of breeding females.The study was carried out in a thermophilous evergreen scrub forest dominated by the holm oak (Quercus ilex), within the Natural Reserve of Castelporziano, along the Tyrrhenian coast of Latium region (41°44'N, 12°24'E). Fifty nest boxes were set up in the study site. Boxes were placed at 1.5 m above ground level and spaced at a distance of c. 20 m from each other, according to a rectangular grid. These boxes were inspected monthly from May 2002 to December 2004 and the trapped dormice were weighted, sexed, aged and marked.The study population showed a very long breeding period as compared to northern European populations. Litters began at the end of September and were observed continuatively until the end of March (n=32). The birth peak (84.3%) occurred in autumn (October-December). Juveniles appeared in November and became abundant in December. Females had usually two litters per year and a two-months span was observed between two litters. Litter size was 4.72 (± 0.26), similar to that reported in literature. Breeding young females were never recorded, according to the general observation that common dormice become sexually mature after their first dormancy season (in this case after their first aestivation). In comparison with hibernating populations, the coastal mediterranean populations of common dormouse show a higher reproductive potential. The extension of breeding season, that lasted seven months (September-March), was probably due to the favourable climatic conditions and the constant presence of flowering and fruiting plants from Autumn to Spring. Owing to the length of breeding season, females had two litters per year showing that the reproduction rate of this population may be twice respect to northern populations. The higher reproduction activity in the autumn may be related to the availability of energetic autumnal food, such as acorns (telemetry observations, unpublished), which represent an important trophic resource for females, ensuring a successful pregnancy and weaning. Moreover, juveniles are advantaged by the mild winter which allows them to grow and forage before the summer dormancy.