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Hazel dormice hold on in biodiverse churchyards

23rd June 2020

Guest blog post written by Sam Devine-Turner, Mammal Detective and Chair of Shropshire Dormouse Group

With a decline of 50% since the year 2000, the hazel dormouse Muscardinus avellanarius is disappearing from the British countryside at an alarming rate. Not only are their numbers dwindling, but they have become extinct in 17 counties since 1885 meaning they are now present in only 32 counties (excluding reintroductions). Changes in woodland and hedgerow management, as well as loss and fragmentation of habitat, are the key drivers of the decline of this species. Climate change is also considered to have a significant impact.

dormouse nibbled nutsDormice are an arboreal species, adapted to living in and travelling through trees, and very rarely going down to or travelling across the ground. They are also ‘sequential feeders’, requiring a variety of foods throughout their waking year. Upon waking from hibernation in spring, dormice will consume the nectar and pollen of blackthorn, hawthorn, and other tree or shrub flowers that have awoken alongside them. During summer, when there are few flowers and no fruits, dormice will eat invertebrates that swarm the canopy trees. And in autumn, in preparation to go into hibernation once again, they will gorge on fruits, seeds and nuts to pile on the calories that will give them a chance at getting through winter.

Ancient Britain was almost entirely forested with an ever-changing mosaic of open glades, bramble patches and scrubby groves amongst the larger canopy trees, maintained by the grazing patterns of herbivorous megafauna and traditional coppicing patterns of humans and providing optimal habitat for the hazel dormouse to move through and feed within. However, as megafauna became extinct and natural coppice products became obsolete, woodland was neglected to become high forest. Furthermore, with humans becoming sedentary and populations increasing in size, woodland was cleared to make way for settlements and agriculture. With these changes, dormice lost both abundance of and quality of habitat on a massive scale.

As if the little critters hadn’t had it bad enough, intensification of farming practices has meant the destruction of many hedgerows; hedgerows that were often the only links between now isolated areas of woodland. In autumn, young dormice will leave mum, fatten up and disperse into unclaimed habitat, where they will hibernate ready for the next year. However, if the patch of woodland they are in is already at carrying capacity, and there are no hedgerows for them to safely travel along to reach other areas of woodland, these isolated fragments of woodland can become population sinks. Furthermore, if they are unable to disperse to and breed with other populations, their genetic diversity may become threatened which can result in local extinctions. Hedgerows that have survived being torn out can, if suitably managed, not only act as links between woodlands but provide enough food and nesting spaces to sustain very small populations of dormice. Neglected hedgerows however, can become thin, sparse and gappy, and over-managed hedgerows may not have chance to produce food, and so for dormice to be able to disperse through and potentially breed within hedges, beneficial management is crucial.

It is worth mentioning that the hazel dormouse is an indicator species; what’s good for the dormouse is good for a whole variety of other species. Generally speaking, the health of the local dormouse population is a good indicator of the health of a woodland. But if dormice are intrinsically linked to woodlands, what is the relevance of burial grounds to their survival?

It is of note that the combined area of all of the churchyards in the UK is the size of a small national park, and a lot of churchyards have intact and well connected boundaries of hedgerows and stone walls, as well as containing small patches of woodland or having untouched ancient woodland immediately adjacent to the churchyard. The variety of food available within and the arboreal links throughout burial grounds like this make them potential havens for the hazel dormouse. Where the small village church and its yard are set within large agricultural deserts, or the town church offers up green space within urban landscapes, they may hold within them the last stronghold of dormice for miles around. And even better, if there are hedgerows or stone walls linking the churchyard to nearby woodlands, they may be an important stepping stone link for dormice within the wider landscape.

Certainly, there seem to be high numbers of dormice within one such churchyard in south Shropshire. During some winter hedge cutting, Caring for God’s Acre volunteers found at least four dormouse nests within the hedgerows surrounding this churchyard. A typical dormouse maternity nest contains an inner ball woven from stripped honeysuckle bark, surrounded by an insulating outer layer of green leaves plucked from the nearby trees, and is found a few feet off the ground in the dense vegetation of hedgerows, scrub, ivy, or the hollows or crannies of trees. During winter, dormice hibernate in small scruffy nests or no nest at all at ground level, in places where the temperature is not likely to fluctuate, such as in log piles, old mouse burrows, or in leaf litter, which prevents them from being roused unnecessarily. The nests found in these hedgerows in south Shropshire were maternity nests, indicating that dormice were indeed using the hedges to breed in.

Dormouse nest leavesInterestingly, this particular church is situated within a ‘V’ shaped parcel of land between two rivers, which are large enough that dormice most definitely cannot cross them. At the back of the church there is a small area of woodland with a variety of native tree species; some understorey species such as hazel and elder, and some tall canopy species as well as, typical to churchyards, some large yew trees. Throughout the area are small patches of bramble and dense piles of brash from previous clearance, and excellently-managed hedgerows provide connectivity to this woodland and through the whole yard. In short, on a very small scale, this single churchyard alone meets the needs of dormice in terms of feeding, nesting and hibernating opportunities. However, considering that dormice usually prefer to breed within woodland upwards of 20 hectares, and an individual male dormouses home range is approximately 0.75 hectares, along with the fact that connectivity to the wider landscape is limited on three sides due to the rivers, it is surprising to find that dormice are indeed breeding within this area.

However, this may be indicative of the state of dormice in the country. As previously discussed, habitat loss and fragmentation are two of the biggest drivers of the decline of dormice and it is likely that this churchyard is incredibly representative of many other churchyards within the species range and certainly within the country for many other species; in that it is supporting remnants of populations by providing the last shred of suitable habitat within an otherwise fragmented and ecologically dead landscape. How much longer can this species hold on if there are no large woodlands nearby suitable to support a genetically secure population, or no arboreal links to such woodlands? We can’t predict this, but what we can say is that without churchyards such as this, with their native hedgerows and patches of woodland, and their local volunteer groups who manage them in traditional ways, the dormouse would most certainly be struggling even more than it already is.

A couple of months after the maternity nests were found, some local residents living close to the church came across a dormouse attempting to hibernate within some scrap they were clearing in their garden. The dormouse was a juvenile, born that same year, and though it was an unusual place to choose to hibernate, it was conclusive evidence that breeding dormice in the area had produced young that had survived. Since contact was made with the local dormouse group, plans are in place to set up a nestbox scheme through the area, which will not only help to build a picture of the population on a local scale now and into the future but will also contribute data to the National Dormouse Monitoring Programme, a scheme set up by the People’s Trust for Endangered Species that informs of national trends of the species. As dormice are a European Protected Species and as such individuals and their nesting and resting places are legally protected from disturbance, Natural England licensed monitors will check these nestboxes, record the numbers of dormice and nests found in the boxes and collect biometric data of any animals found.

What happens next; how do we prevent local extinction of this population of dormice? Caring for God’s Acre volunteers are already managing the site in a way which is beneficial to dormice, and so the next step should be to consider the links to surrounding woodland. This step is always easier said than done, however. Rebuilding links to the wider landscape can require often difficult liaison with local landowners, and it also needs plenty of funding to pay for tree planting and equipment to manage the landscape in a way which is beneficial to wildlife. Furthermore, it requires a huge amount of volunteer time and effort. This is one of the many challenges that conservation organisations and local species groups all over the country face. However, projects such as the National Trusts Stepping Stones, the Wildlife Trusts Living Landscapes and the RSPB Futurescapes Initiative, as well as many more national and local habitat-linking projects, give some hope that we can rebuild the lost links between islands of wildlife across the UK and save our wildlife, including the hazel dormouse, from extinction.

Sam Devine-Turner, Mammal Detective and Chair of Shropshire Dormouse Group