Hazel dormouse Muscardinus avellanarius (L.) nest site selection in hedgerows

The natural nest sites in hedgerows of the hazel dormouse Muscardinus avellanarius were investigated in Devon, in south-west England. A total of 73 nests were found in the autumn by careful searching of hedgerows, all of which were species-rich. In hedgerows that had not been cut for 6 years or more, most nests were in bramble Rubus fruticosus agg. and field rose Rosa arvensis margins, with a few in holly Ilex aquifolium bushes. In contrast, in hedgerows that had been cut within 6 years, the majority of nests were in shrubs, the dense protective growth at the cut line being strongly favoured. Blackthorn Prunus spinosa was preferentially selected, hazel Corylus avellana was avoided. It is suggested that the availability of safe nest sites may limit population density and that where nesting conditions are good the hazel dormouse may prefer to build nests in unenclosed situations rather than in hollows, whether natural hollows, such as tree holes, or artificial ones, such as nest boxes. To encourage hazel dormice in hedgerows, bramble and rose margins should be allowed to develop, and some lengths of hedgerow should be cut occasionally, particularly where blackthorn is present.