Dormouse

Abstract: Summary 1. Habitat loss must be distinguished from habitat fragmentation so that appropriate conservation management can be applied. Few studies have evaluated the independent effects of habitat loss and habitat fragmentation on the distribution of vertebrates, and none has evaluated the independent effect of changes in structural connectivity. We carried out a landscape-scale experiment to assess the independent contribution of these three processes and to examine what landscape scale factors affect the distribution of two forest-dependent arboreal rodents: the hazel dormouse Muscardinus avellanarius and the red squirrel Sciurus vulgaris. 2. Habitat loss, rather than habitat fragmentation per se, was the major driver of distribution patterns for both species. As predicted, structural connectivity (hedgerow networks) played an important role in determining the distribution of the hazel dormouse, but not of the red squirrel. 3. Our models predict that long lengths of hedgerows (>30 km) are unlikely to increase the probability of occurrence of hazel dormouse in landscapes where there are low levels of forest cover (<5%–10%). 4. Synthesis and applications. Our empirical findings indicate that structural connectivity and habitat loss may have additive effects on vertebrate distribution. For the hazel dormouse, improving structural connectivity will be ineffective if the amount of forest cover in the landscape is less than 5–10%. The key message from this study is that resources should not be invested in landscape linkages until their efficacy for the given level of suitable habitat has been assessed.

Abstract: In the last 100 years, the Dormouse Muscardinus avellcmarius has disappeared from about half its geographical range in Britain. Evidence is presented which indicates that declining range and numbers are due to a complex interplay of factors which include fragmentation, deterioration and loss of specialized habitat. The Dormouse is unusual in being a relatively A-selected small mammal, with exacting ecological requirements which render it very vulnerable, particularly to habitat fragmentation. The Dormouse is also sensitive to climate, both directly and probably indirectly through the effects of weather on the timing and abundance of food (insects, flowers and fruits). Combined with low population density and low intrinsic rate of population increase, this makes the Dormouse highly vulnerable, not just to absolute climatic measures (e.g. temperature, rainfall), but especially to climatic stochasticity, particularly at the edge of its range. There are strong associations between the distribution and changing status of the Dormouse and various climatic parameters, and clear parallels with other climate-sensitive taxa, notably bats and butterflies. The Dormouse is a very specialized species, highly sensitive to environmental change, resulting in its piecemeal, progressive extinction, particularly in northern counties. It is likely to be a very sensitive indicator species for monitoring future changing environments and an excellent model for studying the effects of habitat fragmentation, climatic shifts and climatic stochasticity.

Abstract: A stratified sample of 238 woodlands in Herefordshire was surveyed to determine the incidence of dormice in relation to age, area and isolation of the site. Characteristically gnawed hazel-nut shells were sought as indicators of dormouse presence. Dormice were more frequently found in ancient woodland than in recent woodland, supporting a previous hypothesis that they are an insular species. Both site isolation and area influenced distribution, in accordance with insular ecological theory. Prevalence of woodland and boundaries around a site affected dormouse incidence. The results suggest that isolated woodlands less than about 20 ha in extent are unlikely to support viable dormouse populations

Abstract: Population ecology and reproduction of the fat dormouse (Myoxus glis L.) were studied in central Germany in the years 1992 and 1993. Animals were captured in wooden live-traps twice a month, during trapping periods lasting three days each, and marked individually by tattooing. Demographic results show that, in three subpopulations, population structure differed extremely between 1992 and 1993. In 1992, more adult than subadult dormice occurred in the study area and the reverse was found in 1993. Subadults emerged from hibernation a little before or together with adult dormice. Adult males emerged significantly earlier than adult females. After a year with good reproductive success (1992), a total lack of reproduction was observed in 1993. Juvenile dormice were neither found in traps nor in nest-boxes. The assessment of gonadal states indicated that all males (adult and subadult) remained in a state of testicular regression throughout the year 1993. Also, no female was found lactating. Reproductive failure coincided with a lack of food resources in the autumn of 1993 (e.g. fruits of oaks and beeches). Body mass changes imply high energy expenditure prior to mating in adult males. It seems likely that males in years with low food availability do not invest energy in reproduction.