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Hazel Dormouse (Muscardinus avellanarius)

Hazel dormouse, Hazel dormouse



Hazel dormice are small native rodents with golden fur and large black eyes – the only small British mammal with a furry tail. They are arboreal – active in the canopies of trees and shrubs from spring to autumn and hibernate over winter in nests on the ground. The name dormouse comes from the French ‘dormir’ to sleep – a sleepy mouse! They need diverse woodland habitats to provide a wide range of foods including berries, tree buds, flowers, nuts and even caterpillars. They can live for 3 years and breed slower than many rodents, with usually one litter of about 4 young each year.


Historically the dormouse was found throughout England and Wales and up to the Scottish borders. The most northerly population was recently lost from Northumberland. The last existing population in Cumbria is at Roudsea Wood, a National Nature Reserve managed by Natural England. This population is small, yet well established and regular monitoring indicates that while it is relatively stable, there is currently no dispersal from it.

Nationally the hazel dormouse is in decline. This was first documented in 1984 recording a loss of over half of their original range, and more recent research has shown a 72% decline in the population between 1993 and 2014. The dormouse is now classed as ‘vulnerable’ and the most recent Article 17 assessment status is ‘bad’.

Reasons for Decline

The woodland habitat that the dormouse needs declined over the second half of the 20th century. As landscape management practices changed hedgerows were also lost, which destroyed connectivity between woodland fragments. Dormice typically move short distances and need good quality woodland habitat with a range of food species throughout the year. Climate change is also a concern for this species as it effects the flowering, ripening and availability of fruits, seeds and insects and warmer winters can negatively impact hibernation.

Project Aims

Woodland management in South Cumbria has improved in recent years and some areas are now ready to host dormice again. However, because dormice only move short distances, they are not able to recolonise areas by themselves. As part of the National Dormouse Reintroduction Programme, we are planning to release 90 animals into adjacent sites in the Arnside and Silverdale AONB. There is much public support and interest in this species, and we will provide people with opportunities to get involved in bringing them back. Local residents will help make the release cages and feed the dormice as they get used to their new surroundings. Our project will provide training and allow people to become licensed to handle and monitor the dormice. We will host walks and talks to teach people about the species and encourage them to volunteer for the dormouse project. There is substantial interest in forming a local management group that will support the animals into the future.

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