Dormouse dispersal surveys

Photo by Gwen Hitchcock

Volunteers are helping us to monitor populations of hazel dormouse on our reserves and in the wider countryside. Here's an update on what has happened in 2016.

Volunteers are monitoring dormice Muscardinus avellanarius in five areas across Cambridgeshire and Northamptonshire. Over 50 volunteers are out surveying 35 transects across 14 woodlands and farms, all of which have been checked at least once this year. The most important areas have been visited up to five times with the final box checks taking place in October.

One of these important sites is a release site for re-introduced dormice (Brampton Wood), two have native populations recorded and the final two areas are focusing on dispersal from known sites. The study is therefore looking at the full spectrum of dormouse presence and dispersal.

The completed record sheets from 2016 have been entered so we can give you a brief summary to date:

  • Dormice have been found at two woodland sites which support good populations, with young being found at both woodlands: Brampton Wood (13 adults, 12 young) and Fermyn Wood (9 adults, 11+ young).
  • Dormouse nests were found in hedgerows leading out from both woods; the one at Brampton being the furthest from the wood ever found. This is great news as it shows they are spreading out.
  • At Old Sulehay a dormouse nest was found in a farm hedgerow adjacent to another release site, showing that they are moving out if the wood.
  • At Fineshade we found the first dormouse nest recorded on that transect. This was also exciting news as it indicates that, although at low numbers, dormice are more widely spread through the woodland. We are planning to add another line of boxes to this area over the winter to see if we can pick up more.
  • There was a lot of variation in box occupancy*, ranging from 0.4% in some of the hedgerows to 32.7% in the best woodland area. Although the hedgerows by their nature spread away from the core areas so we might expect a lower occupancy.
  • Between the woodlands there was also a lot of variation with only 2% of the boxes in Fineshade being used by dormice, 12% at Brampton and 33% at Fermyn. Whether this variation reflects population size, box density or availability of natural nesting sites could be a topic for further study.
  • We haven’t found any dormice at Stoke Wood End Quarter for many years, making it likely this population is no longer present. It’s worth monitoring the site as it may be the population is at too low a density for us to detect.
  • No dormice were found at Salcey Forest, but we have had reports that they are being found further up the M1 than previously known. Hopefully it’s only a matter of time before they make their way to the site.
  • The boxes have been used by many other animals with wood mice Apodemus sylvaticus being the most prevalent users of boxes. Over 194 individuals were recorded, some with young. Wood mice or their nests were found in 14% of the boxes across all sites.
  • Birds were the next most regular user of boxes, in spite of the new design, with 11% of all boxes containing bird’s nests and many other boxes containing bird droppings. Most commonly found were wrens Troglodytes troglodytes, a small species that can more easily access the box. Blue tits Cyanistes caeruleus and great tits Parus major were also reported breeding in the boxes.
  • Bank voles Myodes glareolus were found in 9 boxes across two sites (Brampton and Stoke Wood End Quarter); but only in boxes in the hedgerows
  • Shrews were found mostly in the woodlands. Pygmy shrews Sorex minutus were the most commonly recorded. Shrews were found at Brampton, Old Sulehay and Fermyn.
  • Pipistrelle bats Pipistrellus pipistrellus were also found roosting in boxes at Brampton Wood (two in a box) and Old Sulehay Forest!

Thank you to everyone who has volunteered their time for this project, it’s an amazing effort! Special thanks to the Activity Leaders who have organised the teams and ensure licence holders can get to every transect as needed. Thank you too to those working behind the scenes making boxes and keeping tracks clear.

*box occupancy being defined here as % of boxes in which a dormouse or dormouse nest was found on at least one occasion.