Dormice in Rockingham Forest
Brambles provide essential food for Dormice
An introduction to Hazel Dormice
by Judy Stroud
On a scale for cuteness, the Hazel Dormouse definitely scores 10/10. With their furry tails, soft golden fur and large eyes they are easily distinguished from other species such as the Wood Mouse. In fact, they are in a whole different family of rodents called the Gliridae. Their long whiskers, another distinguishing feature, are moved back and forth 15 times per second to help them to feel the way in front of them - a very useful trick, as not only are they nocturnal creatures but they also spend much of their time in the shrub layer of woodlands and hedgerows. Only rarely do they come down to the ground. Their arboreal lifestyle is also aided by having specialised pads on their feet, which help them grip onto twigs and enable them to move very fast when the need arises.
Young dormouse in Fineshade Wood
Dormouse nest. Photo c. Gwen Hitchcock
Dormice can live from three to five years and usually have just one litter a year. The four to six young stay with their mother for up to eight weeks until weaned – a long time for such a small mammal. Their intricately woven summer nests are made from honeysuckle bark and other fibrous material and are about the size of a grapefruit with the outer layer often made of fresh leaves. Sometimes they can be found in bramble bushes but are often hidden away in hollow trees, under bark or even in existing bird and squirrel nests.
Of course, another thing that distinguishes dormice from other mice is their ability to hibernate. They spend nearly half of the year hibernating, from around October to April, depending on location and weather conditions.
You may remember the dormouse asleep in the teapot at the Mad Hatter’s Tea Party in Lewis Carrol’s classic novel ‘Alice Through the Looking Glass’. Victorian children used to keep dormice as pets so maybe this sketch wasn’t quite so extraordinary as it seems to us today. At that time the animals were much more common than they are now and country folk would frequently find nests in hedgerows in the course of their work. Even within living memory this was the case.
Dormouse found asleep in a nest box
Dormice hibernate as a way of coping with winter food shortages and the need to conserve energy. In the autumn, they make small, tightly woven nests about the size of a tennis ball in which to hibernate, often under moss or loose-leaf litter on the woodland floor. To prepare for hibernation, they double their weight by feeding on hazel nuts, blackberries and other nuts and fruits. They can only survive in woodlands which have a good diversity of trees and shrubs to provide them with the nuts and berries needed to see them through the hibernation.
Then, when they wake up in the spring, they are very selective in their choice of food. They cannot digest cellulose and feed on the fresh flowers of shrubs and trees to build up their energy and to prepare them for the breeding season. Bramble flowers are a favourite as they have such a long flowering period. As the summer progresses, they feed more on insects that they may find higher in the canopy as well as in the shrub layer.
Dense, continuous, species-rich hedge needed to link woodlands
Blackberries, rose hips and sloes all provide food for dormice before they hibernate
Why have populations declined?
In Victorian times they were found right across England and Wales, but now they are absent from much of the north and midlands of England. It is probable that their arboreal habits, specialised diet and dependence on woodlands with a diversity of trees and a good shrub layer has meant that they are unable to cope well with our modern landscapes. Much of the large swathes of ‘wildwood’ such as the former Rockingham Forest have gone. Here the remaining small isolated woodlands make dispersal between them difficult – especially because they prefer to keep their feet off the ground. Many hedgerows which once connected these woodlands have also been lost and traditional coppicing of hazel is no longer widely practised. Where woods are not well managed they become darker, colder and less diverse. Also, the number of deer has increased greatly over the last century and their browsing effects on woodlands reduces the understorey that is so important to dormice. Again this is particularly true in Rockingham Forest where there are large herds of Fallow Deer and the more solitary Muntjac are now widespread.
Adding to the woes of dormice are the warmer, wetter winters we are now experiencing, associated with climate change. These changes can mean that dormice wake up during the winter on warm days but cannot find any food. They will then use up those carefully laid-down fat stores and as a consequence some find it hard to survive through to the spring.
Unfortunately, climate and weather are factors that we cannot control, but that only makes it more important to help dormice through habitat management and environmental protection. By improving habitats for them, a whole range of other species will also benefit. Reintroducing dormice to the 17 counties from which they have been lost is another ‘string to our conservation bow’ together with the need to increase populations at the edge of their range. So far there have been over 30 reintroductions to 25 sites in 13 counties, which is a huge achievement. It all started as part of the English Nature Recovery Programme in the 1990s and is now co-ordinated by the Peoples Trust for Endangered Species (PTES), who also run the National Dormouse Monitoring Programme (NDMP).
One of the reintroduction sites is Bedford Purlieus which lies within Rockingham Forest. During the clearance of over 600 acres of the Purlieus between 1862 and 1868 dormice were sometimes found when men were grubbing up the tree roots. No evidence of dormice was found there during the late 20th century but the wood met the criteria for a successful reintroduction. This took place in 2001 and monitoring by the Forestry Commission has shown a long-term success, with dispersal within the wood from the initial release site.
Checking a typical nest box
Monitoring of dormice populations has traditionally been carried out as part of the NDMP using specially made wooden nest-boxes. Up to six times a year specially trained and licenced volunteers check the boxes for summer nests and animals. Dormice are protected by law so anyone disturbing or wishing to handle a dormouse needs a licence from Defra or must work alongside a person with the relevant licence.
This can limit surveying effort but an ingenious method of checking for the presence of dormice has been developed recently that doesn’t require a licence. It involves volunteers checking for footprints left on cards in special tubes. The specialised pads on a dormouse’s feet leave very distinctive footprints. They are also naturally inquisitive and will readily enter a tunnel hung in a bush, walk over an ink pad. They then leave prints on a paper tunnel floor before continuing on their way. This was used for the first time in Fineshade Wood in 2022 with 50 tunnels put in place and checked every 10 days during the summer. You can read about the Tracking Fineshade's Dormice project here.
Both of these survey methods require perseverance and it is to the volunteers’ credit that they have continued to be enthusiastic when positive results are not very frequent. Dormice live at low densities and have many natural nest sites in optimal woodland sites. The chances of finding nests or dormice in boxes or footprints in tunnels are far from guaranteed even with a healthy population. Over the last 10 years or so, two dormice and a handful of nests have been found in boxes in three small areas of Fineshade, although they are more regularly found in Fermyn Woods. Footprints found in 2022 in several of the 50 tunnels in Fineshade demonstrated that the animals are present in a fourth area of that wood – a great boost to volunteer morale. Monitoring will continue in the years to come and the footprint tunnels will be moved to new areas in Fineshade and elsewhere to help our understanding of where dormice occur within Rockingham Forest.
Rockingham Forest is near the northernmost limit of naturally occurring populations, making it a very special area for dormice. Monitoring is showing us that they are still here in very small numbers but it is clear that positive habitat creation and management is needed to bolster the fragile Rockingham Forest population and prevent further range contraction. We need our woodlands to be better managed; we need more of them and they need to be much better connected,
There were other woods in the Rockingham Forest area where dormice were recorded in the recent past and there may well be other populations yet to be discovered. If you would like to be involved with helping the work for dormice in Rockingham Forest please email Gwen Hitchcock.
English Nature's Dormouse Conservation Handbook (second edition) can be read and downloaded here.
Heavy deer grazing has removed all the understorey
Good, tangled understorey with light filtering through
Coppiced hazel with honeysuckle - ideal for dormice!
Additional monitoring by Ecology Group volunteers from the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire (WTBCN) has also found evidence of dormice dispersing on the western side of Bedford Purlieus in hedges leading towards Easton Hornstocks and Collyweston Great Wood.
Elsewhere in Rockingham Forest, monitoring since 2011 by WTBCN volunteers, has also found evidence of natural populations of dormice in Fermyn Woods and Fineshade Woods. They were present in Stoke Wood, near Corby, in the 1990s but no recent evidence of their continued presence has been found since 2000.
Weighing a dormouse
Footprint tunnel in Fineshade Wood
Handling dormice needs great care - and a licence!
About Judy Stroud
Judy is a wildlife ecologist and has worked for Natural England and its predecessors in various guises including dormice licensing. Since leaving NE in 2012 she has been able to spend most of her spare time away from computers and learning more about wildlife first-hand.
She has had a long interest in Northamptonshire's wildlife, and has been monitoring dormice as a volunteer with the local Wildlife Trust for over 15 years.