DORMOUSE HABITAT PREFERENCES
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CAN HAZEL DORMOUSE HABITAT BE QUANTIFIED BY NESTING BEHAVIOUR? THE INFLUENCE OF VEGETATION DIVERSITY AND STRUCTURE HAMISH JACKSON Introduction The UK population of hazel dormice (Muscardinus avellanarius) is estimated to have declined by 72% over 22 years from 1993–2014 (Goodwin et al. 2017) and this decline is ongoing. The reasons for this are poorly understood, but are likely due to anthropogenic fragmentation of habitat and changes in climatic conditions. Dormice are considered vulnerable to fragmentation because the species is primarily arboreal and does not travel large distances across open ground (Bright 1998). Therefore, extreme cases of fragmentation are likely to cause local extinctions when populations become too small to be viable (Morris 2004). Milder and less predictable winters in Britain are also considered to cause the species to awaken prematurely from hibernation. This would cause a dormouse’s energy reserves to be consumed quicker and would result in a higher potential a higher mortality rate (Juškaitis 2008). As dormice are rapidly declining it is important to examine their habitat requirements to apply effective conservation strategies. Dense vegetation structure and complex plant diversity have been cited as critical elements in defining dormouse habitat suitability (Combe et al. 2016). It is also considered that specific plant species are especially important for dormice populations. In particular, bramble (Rubus fruticosus agg.) and hazel (Corylus avellana) are perceived as important long-lasting food sources, essential for gaining body weight for hibernation in the autumn (Morris 2004; Juškaitis 2007). Oak (Quercus robur) is also considered a valuable food source for dormice as it provides an abundant source of insects during the spring and summer. However, none of these species are essential for viable populations as the species can adapt to survive in a range of habitat types (Juškaitis & Büchner 2013). This investigation was undertaken to determine whether dormice presence is influenced by different vegetation composition, individual plant species and vegetation structure in the East of England. Method The investigation took place in Suffolk and the north of Essex. Sixteen sites were examined, representing a variety of woodland, scrub and hedgerow habitats. Surveys for dormice evidence were undertaken at monthly intervals between March and November 2016 by the Essex and Suffolk Dormouse Group, using nest tubes as a recording method (Plate 10). At each site 50 tubes were placed in woody vegetation along a transect at 15–20 metres spacing. Overall, 800 nest tubes were examined and at each nest tube location vegetation sampling within a nested quadrat of 5m 2 and 10m2 was undertaken. Within the quadrat, a count of all the woody species was provided as well as the estimated percentage cover of each woody species using a Braun-Blanquet scale. Structure was examined by assessing the canopy height, understory density, bramble height and canopy cover at each location.
Trans. Suffolk Nat. Soc. 53 (2017)