Ontogenesis of pelage and the course of moulting in Microtus

Two methods are used in the investigation of the development of für and moulting in small mammals. The most common way is to observe the pigmentation of the skin. We have used a more recent method, staining the whole animal with Standard hair colours and observing changes in pelage patterns. It is thus possible to investigate ontogenetic changes in voles, and also the influences of different conditions of photoperiod and temperature on moulting. Contrary to the Information in the literature, we found that newborns of M. brandti are pilose. Düring ontogenesis the following moults take place: I. Moult into the second immature pelage, II. moult into the first mature pelage, III. seasonal moultings (spring and autumn). Moults I. and II. occur, depending on the age of the animal. Like other Arvicolidae M. brandti shows a sublateral course of moulting. The moult of the ventral body side is completed before the dorsal side. Deviations from this scheme, so-called "moulting variants", are possible. Within one population of M. brandti the spring generation passes through five moults and the autumn generation through only four in the first year of life. Because of the shortened duration of moulting during low temperatures the first moults of the autumn generation are faster than those of spring-born animals. These results represent a prehminary attempt to clarify conflicting observations on moulting from field investigations of small mammals, involving, in most cases, animals of different age classes and generations from one population.