Why are Hazel Dormice Endangered?

Many developments have to include habitat surveys and mitigation plans if hazel dormice are found near properties or within the land going to be developed for housing. Often one of the questions Acer Ecology gets is why do these have to go ahead? Read on to find out why!

The Hazel Dormouse

Hazel dormice are not actually mice; this tiny little nocturnal mammal is more closely related to squirrels and beavers! The word ‘dormouse’ originates from the world ‘dormeus’ which translates to ‘sleepy one’ – aptly named as they sleep for the majority of the year. They are arboreal mammals, which means they spend a lot of their time in trees and are highly acrobatic.

Dormice worldwide

There are also up to 29 living species of dormice found worldwide that are all classified within the family Gliridae; one of the oldest rodent families in the world, dating back 40 million years. Dormice can be found in North Africa, Sub-Saharan Africa and western and central Asia, as well as in Europe. They can all be found in similar habitats to the European hazel dormice: in forested, woodland and scrubland areas. Throughout the world this species of rodent plays an important part in food chains and are a good indicator of animal and plant diversity in an ecosystem. A drop in its population can have a ripple effect within food chains and have dire effects to other wildlife populations.

Where do they live?

Hazel dormice in the UK are found mainly in southern England, southern Wales and along the English/Welsh border. However, these populations are considered extremely sparse and patchy. Dormice like to live in lots of woody vegetation, generally the succession stage of woodland growth. They are associated with scrubland, old overgrown hedgerows and old coppice woodlands.

What is a Hazel Dormice lifecycle?

dormouse year

Hazel Dormice in the UK

Dormice are the only UK dwelling rodent with a fluffy tail, which they can shed in the event of an attack by a predator. They spend the majority of their time in the branches of trees and are found either within bird’s nests or within nests that they have woven themselves. Hazel dormice often have one litter with up to four within a litter. Their diet is mainly plant based depending on the season, flowers, nectar, and nuts, they will also feed on a variety of insects when the opportunity presents itself. Dormice have a few predators such as owls, weasels, cats and even grey squirrels whilst they are active in the summer months. Whenever the weather is particularly bad, this little rodent can go into torpor (can sleep for short periods of time) until the weather is suitable again, so as to save energy. They go into hibernation during winter and can be found curled up in leaves under the edge of hedgerows. During their hibernation period they can be predated on by badgers and wild boar, however their main threat is surviving all the way through winter.

Why are they endangered in the UK?

Hazel Dormice in the UK are a protected species. They are very rare and vulnerable to extinction, which has caused them to become a priority species in the UK Biodiversity Action Plan, as well as being protected under the Wildlife and Countryside Act 1981. In 2017, the population plummeted by 72% within the last 25 years.

Why are they so vulnerable?  They tend to be very slow breeders and do not disperse as well as other species. Their habitat tends to be of old woodland linked by well-established hedgerows. The growing human population, habitat fragmentation, the lack of management of woodlands or their removal, has caused the reduction of suitable habitat, leading to the drop-in dormice population. As they do not disperse very well, any newly managed woodlands that have lost their dormice populations may never regain them. Climate change is another potential factor that could affect this delicate species, however, the impact is unknown.

There is Hope! Although this species has been undergoing dramatic declines in numbers over the last few years, it seems that the decline is actually slowing, and a dormice reintroduction programme has been implemented and will be potentially extended due to this positive information. There is also 25 years’ worth of monitoring in the UK that has been conducted by volunteers and scientists to try and better understand and protect this species.

Signs of Dormice in the Wild:  One of the most characteristic signs of a hazel dormice being present in an area is due to the way they eat hazelnuts. They gnaw a round hole in the shell of the nut which leaves distinctive marks. The tooth marks made by dormice tend to run parallel to the edge of the hole, so this makes the rim look smooth, with very little marks on the outside. Other species of rodent who feed on hazelnuts also have toothmarks, but these run outwards. Another sign of dormice in an area is their tightly weaved nests, which can be found throughout the year in two forms, a summer nest and a hibernation nest.

What can I do to help?

Take part in dormouse monitoring programmes – this is the best way to try and closely monitor the health of the population, the species whereabouts. Also to try and assist their survival by putting out nest boxes for them.  To find out more, follow this link to the People’s Trust for Endangered Species.



 Author: Ashley Dale