Patterns of tooth crown wear in Dryomys nitedula (Mammalia, Rodentia): age-related variation in the light of annual cycle specifics based on museum collections

Abstract

We analysed the specifics of age-related variation of tooth crown wear in Dryomys nitedula from Ukraine. The study is based on a morphological sample of 101 specimens (study-skins and skulls), which have been amassed in zoological museums of Ukraine since their establishment. Results suggest that patterns of enamel wear are closely related to the specifics of the species’ annual cycle, in particular to periods of activity and hibernation. It was revealed that the longest period of the species’ activity lasts 5.3 months, and, respectively, the forest dormouse hibernates during not less than 6.5 months. Based on the level of enamel wear, an improved method of age group determination was developed and applied successfully. Six age groups were selected that largely differ by the number of respective specimens with a clearly expressed decrease from the group SAD1 to group SEN. Similarly, there is also a clear decrease in the duration of active phase of annual cycle among subsequent age groups: in groups JUV to AD1, the active period lasts 6 months, while animals of age groups AD2 to SEN are active only for 1 to 4 months. The period of recorded activity decreases with the age determined by the level of tooth crown wear. Morphometric data presented suggest that definitive means of morphometric characters are already formed until the first wintering. We also discuss the absence of young specimens in the samples and the sharp decrease in the number of adults (age groups AD2 and SEN). Most of the species’ records are from the forest steppe zone of Ukraine and the portion of the forest dormouse in forest steppe communities seems to be extremely low (its catches on trap-lines are rather occasional).