In a recent study, researchers led by the University of Exeter have highlighted the importance of woodland management for dormouse conservation…
Woodlands require management for a variety of purposes. Integral to this management is the consideration of protected and notable species such as dormouse, and the requirement to reduce or mitigate actual or potential harm caused by management activities; current measures are often based on incomplete information regarding the response of protected species to tree removal.
Populations of hazel dormouse in the United Kingdom have declined massively in the last thirty years. This decline is believed to be as a result of climate change and changes to woodland composition. Dormice are often associated with successional woodland habitat, therefore, appropriate woodland management is imperative to providing optimal conditions.
Using remote sensing data it is now possible to study different activities of dormice relating to both ranging and resting, and assess behavioural responses to environmental change. Through understanding habitat preferences, it is possible to predict outcomes of change.
Research and results
Researchers looked at the ranging behaviour, preferences for tree species and vegetation structure of hazel dormice in two comparable woodlands located in Kent and Devon — focusing on the effects of tree felling. Dormice were tracked in areas where tree felling occurred and in areas where no tree felling was undertaken, as a control.
A total of sixteen dormice were successfully tracked for thirteen days or more. The study found that the mean range area was 0.51 ha and the mean core area was 0.09 ha; the mean number of resting sites for each dormouse was 2.7; the mean night-time distance ranged was 46.3 m; and 43% of resting sites comprised dormouse nest boxes, the remaining resting sites comprised abandoned squirrel dreys, birds’ nests, tree hollows, low shrub, a tree guard and a tree stump.
The sex of the dormice and site did not significantly affect the ranges or the mean distances travelled from resting sites. However, heavier dormice were found to use smaller ranges and didn’t travel as far from resting sites as lighter dormice.
The structure of vegetation was shown to strongly influence ranging behaviour. Dormice were found to prefer mid-height woodland habitat – 5–10 m tall – with low proportions of high forest – over 10 m tall. Preferential areas comprised edge habitats, internal edges between woodland stands, and external woodland edges – thought to be preferred due to increased light and warmth promoting fruiting and flowering, which in turn provides food for dormice (Juškaitis, 2007). Yew, rowan and hazel were favoured during ranging activity.
Areas selected by dormice for daytime resting had a greater proportion of 5–10 m trees, less variation in canopy height and a lower proportion of trees over 10 m. Resting sites were typically located within the core areas of dormice ranges, where protection from weather and predation is higher. 67% of natural dormouse nests were associated with old growth, highlighting the importance of retaining mature trees and old-growth features.
The study noted that populations may be more flexible in their habitat use when more or different habitats are available – the woodlands used in the study did not have an understorey layer. Bright and Morris (1992) found that dormice use different vegetation heights depending on the seasonal availability of food.
Tree felling was found to have no effect on the nightly distances travelled by dormice. However, in areas where trees had been felled, there was less evidence of a shift in ranging area for dormice than in unfelled areas. This could represent a ‘hiding’ response.
Tree felling in the study was undertaken for conservation purposes – commercial felling leads to much greater vegetation disturbance, habitat loss and fragmentation. Even so, the study notes that the noise and disturbance of small-scale felling is considerable. Surprisingly, the majority of dormice did not flee from the disturbance, suggesting that large-scale felling could have impacts on dormouse survival (Blumstein, 2010, Escobar et al., 2015).
Implications
The implications for conservation and woodland management that can be drawn from the study are summarised as follows:
- planting and retention of mid-height trees of 5–10 m and edge habitats, in addition to reductions in high forest, will increase the amount of resting and ranging habitats for dormice
- old growth features and mature trees should be retained to provide adequate nesting opportunities
- a dense, highly connected layer between trees should be maintained in order to allow for increased ranging movements
- the promotion of preferential trees species — yew, rowan and hazel — will provide autumn habitat for dormice
- preferred food plants should be distributed across woodlands to increase their carrying capacity and population abundance.
The findings that dormice did not flee from small-scale tree felling could have survival implications for individuals and may need to be mitigated for. However, preferences for habitats that generate after tree felling and clearance, emphasise the need for active management in order to maintain optimal habitat for dormice. A trade-off may therefore be required between short-term negative consequences of forestry operations for individual dormice and long-term beneficial effects of management for dormouse populations.
Reference:
Open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0).
Header Image: Zoë Helene Kindermann/Wikimedia Commons.
About the Author: Kate Priestman (CEnv, MCIEEM), Co-Founder and Editor of Inside Ecology, has over sixteen years experience as an ecologist. Prior to setting up her own consultancy business in 2012, Kate worked in London for over a decade, providing the lead ecology role for a number of high profile projects. In addition to running Inside Ecology, Kate works as a freelance writer, author and artist.
