The Hazel Dormouse AKA ”The Sleepy One”

Oh, To Sleep!

With the number of dusk and dawn bat surveys we’ve undertaken this season approaching 200 between us, it is refreshing to survey dormice once in a while. It seems especially fitting as we have come to identify with the etymology of the word ‘dormouse’ which some sources reckon comes from the Old French ‘dormir‘ meaning ‘to sleep’. ‘To sleep’ is definitely something we aspire to!

Muscardinus avellanarius [HAZEL DORMOUSE] England 2017-09-09Click to zoom in

Dormouse Box Checks

On these occasions, we have been venturing out into the midday sun to help with dormouse box checks in a few areas of North Somerset.

Click to zoom in

During our surveys, we check man-made dormouse nest-boxes that are attached to trees sporadically throughout a given woodland. When an occupied box is discovered on a survey, the entry-hole is bunged, and the box is placed in a clear plastic bag. The bung and the lid of the box are then removed. The dormice are collected, sexed, weighed and scanned for a microchip. If a dormouse is large enough and hasn’t been microchipped, one may be inserted as this helps us understand the movements and life of an individual.

Muscardinus avellanarius [HAZEL DORMOUSE] England (1) 19.06.2017
Mr. Jamie O’Connell handling a hazel dormouse

Click to zoom in

Dormouse Checks.jpg
Tom and Emma checking dormouse boxes

Signs of Dormice

Finding dormice isn’t a sure thing on a survey. More often than not, there is a lot of investigating the signs of dormice. We look at the nests within the boxes, as well as the browse on the discarded nut shells.

Dormouse Nests

Dormouse nests are well structured with honeysuckle bark and other strips of foliage weaved into a ball with a central cavity, surrounded by a variety of leaves that make up the outer layer. The presence of fresh, green leaves is often a good sign of a dormouse nest.

Nests of birds are usually made of twigs and moss, and nests made by mice are without structure and often have a musky smell to them.


The browse marks on the shells of nuts left by small mammals can be used to identify the animal that ate them. Nuts gnawed on by dormice have an almost perfect circular hole with the inner edge carved out parallel to the edge of the hole. The outermost layer of the nut may have perpendicular gnaw marks.

Large animals, like squirrels, can just crack open nuts leaving untidy sharp edges. The yellow-necked mouse, wood mouse, and voles leave gnaw marks that are perpendicular to the hole leaving a milled edge.

Take a look at this illustration from the PTES website:

PTES Illustration of Chewed Nuts

Hazelnuts with signs of dormice browseClick to zoom in

Who Else is Living in Here?

Inhabitants of dormouse boxes are not exclusively dormice. It is not unusual to find a yellow-necked mouse, wood mouse, bird, bat or selection of invertebrates. Some of our most recent non-dormouse residents included this little pygmy shrew and a wood mouse.

Sorex minutus [EURASIAN PYGMY SHREW] England, 2016-09-24Click to zoom in

Dormouse Biology and Interesting Facts

– A 2016 study found that hazel dormice in Britain have declined by over one third since 2000

–  Hazel dormice are rare and vulnerable to extinction in the UK and are a priority species in the UK Biodiversity Action Plan and are protected under the Wildlife and Countryside Act 1981

– The main threats facing dormice include habitat modification and destruction, as well as climate change

– Dormice are arboreal and will not go onto the ground to cross large open spaces (this means that many populations are isolated)

Click to zoom in

– The hazel dormouse is the only living species in the genus Muscardinus

– They are nocturnal, spending the majority of their time in the trees searching for food

– They hibernate from October through to March

– During the summer, if the weather is not favourable or food becomes scarce, they are able to go in to torpor (a state of decreased physiological activity)

– They live in deciduous woodland, hedgerows and dense scrub

– They can live for around five years

– Dormice eat: nuts (hazel being their primary food source), berries, young leaf shoots, flowers and insects (such as aphids and caterpillars)

Click to zoom in

Want to Know More?

Check out the ‘References & Further Reading’ section below, or ask us a question in the comments!

Muscardinus avellanarius [HAZEL DORMOUSE] England 2017-09-09 #4Click to zoom in

References and Further Reading

Country File Website, 9 Fascinating facts about dormice –
(Retrieved 28 Septemeber, 2017)

Country File Website, 11 Fascinating facts about the hazel dormice –
(Retrieved 28 Septemeber, 2017)

Merriam Webster Dictionary Website, Dormouse –
(Retrieved 28 Septemeber, 2017)

The People’s Trust for Endangered Species Website, Common Dormouse Facts –
(Retrieved 28 Septemeber, 2017)

The People’s Trust for Endangered Species Website, Dormouse Handbook –
(Retrieved 28 Septemeber, 2017)

Wikipedia Website, Dormouse –
(Retrieved 28 Septemeber, 2017)

Wildlife Trust Website, Common Dormouse –
(Retrieved 28 Septemeber, 2017)

The Wooland Trusts Website, Hazel Dormouse –
(Retrieved 28 Septemeber, 2017)

13 Comments Add yours

  1. They look as cute as the dormice in my picture-book when I was a little kid! Lovely blog-post!

    Liked by 1 person

    1. Thank you, Liz❤
      They really are ridiculously adorable, aren’t they?! 😊 Which picture book did you used have?

      Liked by 1 person

      1. Absolutely! Unfortunately I have no idea of the book title. It was a hand-me-down book and quite old even when I had it!

        Liked by 1 person

      2. Interesting! The only dormouse character I knew of was the Alice in Wonderland dormouse: 😀

        Liked by 1 person

  2. Very interesting blog. The Dormouse is a mammal I’m hoping to see one day. Unfortunately there aren’t any or many Dormice in Oxfordshire.

    Liked by 1 person

    1. Thank you, Alex! I didn’t realise that there weren’t many dormice in Oxfordshire. Do you know why that is?


  3. Batnovice says:

    I’d be interested to know how you microchip dormice, it would be very useful to start chipping our local population.

    Liked by 1 person

    1. Hi Batnovice, thanks for reading and commenting. I hope you enjoyed the post.

      What a good question. We understand you need a level 1 licence to handle Dormice and a level 2 to clip their fur for identification purposes, but require a personal licence for anything that is not covered by the level 1 & 2.

      We do not carry out the microchipping ourselves, so have contacted those that do and will await their response. Stay tuned.



  4. Fascinating post, thank you.

    Liked by 1 person

    1. Thanks for your comment. We’re glad you enjoyed it! 🙂🌿



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s