Traces of chewing bark and wood? – A microwear study of Castor fiber (Rodentia: Castoridae) [Stopy po žvýkání kůry a dřeva? – Mikroskopická studie obrusu u bobra evropského (Castor fiber) (Rodentia: Castoridae)]
Tooth microwear analysis has been used repeatedly in the last decades to reconstruct diets of fossil mammals in comparison to recent ones and works well if the modern analogue has a characteristic miocrowear pattern. Here the microwear pattern of cheek teeth in several enamel bands of 20 specimens of the Eurasian beaver (Castor fiber) have been studied and were compared to data of mixed feeders and browsers from the literature as well as to nutria (Myocastor coypus) and muskrat (Ondatra zibethicus). The wear and microwear of incisors is only qualitatively described and consists of parallel broad scratches and few irregular pits and gauges on the lingual dentine facet, as well as irregularly distributed fine scratches on the enamel side. The microwear of the cheek teeth of beavers is dominated by fine scratches and shows few pits and gauges. The variability in the amount of scratches, pits and gauges is very high between individuals, different teeth and different enamel bands. Significant statistical differences in the occurrence of some microwear features were observed between p4/m1, p4/m2, p4/m3 and between P4/M3. Some significant differences between anterior and anterior hypoflexus were observed, but as none occurred in mandibular teeth are difficult to explain. The microwear pattern in Ondatra and Myocastor is similar but shows fewer scratches and relatively more pits. Comparable data for microwear of Myocastor obtained with a different method shows overall slightly more scratches, pits and gauges, which could indicate that the method used here underestimates the features by a certain small amount. This raises the question about comparability of microwear data found with different methods. Compared to the microwear signal of average pits versus average scratches in ungulate browsers, grazers and mixed feeders obtained with the same methodology used here, beavers show few pits and a moderate number of scratches and fall at the lower range of mixed feeders and the edge of the range of grazers. Muskrats and nutria are separated from beavers by the amount of average scratches and fall at the lower range of mixed feeders and at the edge of browsers compared to ungulates studied. However, no differentiation of the three species was obtained in discriminant analyses using all microwear features.