Variation in the tooth wear of the shrews Sorex araneus and S. minutus

Abstract

Tooth wear was studied in 1040 S. araneus and 201 S. minutus in Southern Finland. Total height, as well as the absolute and relative amount of tooth pigment, was measured from the first molar in the lower jaw (Mj). During the whole life span of the shrews, the average tooth wear/month is 39 pm in S. araneus and 26 |im in S. minutus. However, clear differences in tooth wear exist between year classes: wear is almost twice as fast in sexually mature overwintered adults as in immature current-year juveniles. This difference is even greater in the relative height of tooth pigment (pigment index). Differences between age groups in tooth hardness or in the amount or quality of food eaten are suggested. There is sexual dimorphism in tooth measurements (significant in S. araneus): males have lower means in tooth height and in pigment index especially for adults. In juvenile shrews, great differences in tooth height, pigment index and body size exist between years, tending to be higher during rainy summers. This probably is a result of different availability of food between years, resulting in differences in tooth size or tooth wear, or both. Method of measuring tooth height is a better method for differentiating year classes than the method for measuring tooth pigment. The amount of tooth pigment exhibits sexual dimorphism and is more susceptible to measuring errors.