Hazel Dormice, once widespread across the country are now restricted to the south and face further threats due to the loss of ancient woodland, climate change, clearance of hedgerows and a lack of coppicing.

As an arboreal species, dormice rarely descend to the ground apart from when they are hibernating and now a new study from Manchester Metropolitan University’s Dr Robyn Grant, Lecturer in Environmental Physiology and Behaviour, has shown how gaps in tree canopies are leaving these endangered creatures unable to cross between habitats using their hypersensitive whiskers.

Dr Grant recorded high-speed videos of dormice and their whisker movements using a camera that captures 500 frames per second, with the videos proving that gaps in the tree canopy are now a major problem for the dormice.

“Although dormice can jump quite large distances, when the gaps between platforms were larger than 10-15cm, the dormice started behaving differently – they would eat less of the food available to them and also spend more time travelling on the floor as opposed to the canopy,” he explained. “This behavioural change would put the dormice in danger as this species is vulnerable to threats on the ground.”

The total adult population of hazel dormice in the UK is now thought to number about 45,000, distributed among a variety of widely fragmented sites. The UK Mammal Society Dormouse Survey in 1984 showed the species has been lost from seven counties in north and east England in the last 100 years. Even in optimal habitats, population densities are less than 10 adults per hectare.

Large numbers still live on the Isle of Wight and although dormice are widely distributed in Wales, individual populations are small, scattered and isolated from each other. Building hedgerows, habitat corridors and dormouse bridges is critical to this species’ survival.

Carried out at the Wildwood Trust in Kent, Dr Grant’s research into this endangered species was published in the Journal of Comparative Physiology, and shows that dormice use active whisker sensing, with footage revealing that dormice actively and purposefully move their whiskers to gather relevant information from their canopy at night.

Like other rodents, dormice move their whiskers back and forth continuously in a motion called ‘whisking’ to navigate small gaps and to explore their environment.

Dr Grant adds: “Dormice are nocturnal and arboreal – meaning they spend most of their time in branches of trees off of the ground. Their movement within this canopy relies on their whiskers. Hearing, vision and smell also play a role in guiding them around their environments.”

The preservation of the dormouse is critical since these rodents are a ‘flagship species’, (meaning that careful management of dormice habitats will benefit a range of other species). They are also important as ‘bio-indicators’ as they are particularly sensitive to habitat and population fragmentation. Their presence should indicate that the area can sustain populations of other sensitive species

Get Involved

There are ways in which you can help to secure the future of the Hazel Dormouse. As they are fully protected by law they should never be disturbed but you could get involved in a local survey.

Total population size can only be estimated, based upon results from trapping, nest box surveys and reintroduction numbers but researchers say they would have a much better idea of how the species is doing if lots of people got involved with official nest box surveys.

The National Dormouse Monitoring Program is coordinated by the People’s Trust for Endangered Species (https://ptes.org/campaigns/dormice/) and training courses for handling are conducted at the Wildwood Trust in Kent (https://wildwoodtrust.org/wildwood-kent/conservation/conservation-courses).

So if you think there are dormice near you, you could start your own monitoring programme.

Dr Grant’s research was carried out in collaboration with the University of Sheffield and is funded by a British Ecological Society (BES) Research Grant. You can see footage from the new research here:

Video 1: Dormice using whiskers to climb: https://www.youtube.com/watch?v=ZG38zbYAKOk 

Video 2: Successful jump: https://www.youtube.com/watch?v=LDSDNUcB90o

  Video 3: Struggling to cross a gap: https://www.youtube.com/watch?v=VgnffYYsVAs

You can read Dr Grant’s full study here.

This Author

Laura Briggs is the Ecologist’s UK-based reporter

You can follow her here @WordsbyBriggs