The different effects of periodic experimental tree removal patterns on the population demography of the hazel dormice (Muscardinus avellanarius) in a conifer plantation

Abstract. Within a conifer plantation, hazel dormice (Muscardinus avellanarius) were individually marked from 2000 to 2016. In four adjacent experimental study areas (ESAs) of 3 ha each, a different method of restoration of a Planted Ancient Woodland Site (PAWS) was carried out in autumn 2003 to remove ca. 33 % of conifers. A third of those left were removed in 2009 and in 2015. The effects on dormouse abundance indices were recorded by routine monitoring of nest boxes, including marking individuals. The overall number of dormouse captures varied from year to year, increasing the year following forestry operations in 2003 and 2009, possibly because nest boxes temporarily became more attractive. The numbers of individually marked adults showed a stable trend but less variation. The numbers of small juveniles recorded appears to be rising in recent years, suggesting a positive impact during the later stages of this conifer forest reversion. The overwinter survival index of marked juveniles fell significantly for those born the year after each forest operation but not those alive when the felling took place. Adult survival did not fall in either year. Initially, dormouse populations were sustained in each ESA after management and the numbers were not significantly different between the treatments. After the 2009 operation dormouse numbers fell significantly in the traditional mechanical area-wide forest thinning treatment and low abundance has continued. This study demonstrating maintenance of a population of a European Protected Species has important implications for managers and we suggest similar forest management considerations are incorporated into policy and best practice guidelines. The results so far suggest that a patchwork regime type of conifer removal regime can be chosen to be both pragmatic for an economic forestry business and ensuring dormice remain in the local forest.