Surveyor Blog: A Furry Fire Risk

Written by our Senior Regional Surveyor, Hugh Riley.


What’s edible, small and furry, a foreign import, confined to a limited (but expanding) geographical area in the South – and could result in a house burning down? Those surveyors practising in the area will instantly recognise these characteristics as that of a Glis Glis (Myoxus glis).

What are Glis Glis?

Glis Glis look like large mice with squirrel tails and are often mistaken for squirrels. However, they are smaller and not related. They have greyish brown fur and squirrel like bodies up to 19cm long with a slightly darker bushy tail some 13cm long. The inner surface of their legs is white to pale buff and there is a ring of black hair around each eye. They are roughly twice the size of a normal dormouse. They are nocturnal and good climbers, using sticky secretions of plantar glands when they are climbing on smooth surfaces to prevent them from falling. Glis Glis can live for up to 12 years, with the female giving birth to between 4 and 11 young every breeding season.

The Glis Glis was originally farmed and eaten by the ancient Romans – hence its nickname of the “edible dormouse”. The Romans served them either, roasted and dipped in honey, or stuffed with flavourings. Wild edible dormice are still consumed in parts of Slovenia and Croatia.

A European import, not native to the UK, it is rumoured that they were first introduced by the 2nd Baron Rothschild, at his estate near Tring in 1902. A number escaped and it is now estimated around 30,000 inhabit, as an invasive species, an area predominantly around the Chiltern Hills that covers Buckinghamshire, Hertfordshire, and Oxfordshire. In recent years however, there have been sightings on the edge of London and Essex. The extent of the spread is not fully known. Today, the introduction of new, wild, species is prohibited by environmental laws, but at that time no one had any concern for the long-term implications of releasing what is, in effect, a pest into the UK.

The small litter size and a small number of litters per year, together with action of natural predators (owls, foxes, pine martens, and wildcats) mean that Glis Glis do not multiply out of control the way that rats and mice do. However, they are slowly extending the infested geographical area. This will be aided if there is a tendency to warmer spring and summer weather affecting hibernation cycles.

What risks do Glis Glis pose?

Glis Glis normally live-in woodland areas and feed on nuts, berries, pinecones, seeds, and other fruits, but problems arise when they hibernate (from November to May), concealing themselves in softer nesting materials within loft spaces or cavity walls where they can be heard as they run through. They will use a variety of materials to create their nests, including insulation and wood chips, as well as items stored in the loft. Belongings may also become contaminated with urine or faeces.

As a rodent their front teeth constantly grow, like rats and mice, this means they constantly gnaw to prevent the teeth growing into their skull. They often gnaw wood, metals such as copper and aluminium, plastics, and other materials. This can be very loud, and in mating season (June to mid-August) the males are particularly noisy. Within homes they are generally regarded as a pest due to the fire risk from gnawed electrical cables and fouling from their faeces. Some house fires have been directly attributed to electrical fires caused specifically by wires chewed by Glis Glis. They can make quite a mess of a loft space in a relatively short time. The more common and widespread rodents: rats and mice are also equally capable of chewing electrical cables and causing fires – this is a good reason to make sure homeowners have upgraded to a modern consumer unit with RCD protection.

The most common indication that a homeowner has a problem with Glis Glis is noise. After their hibernation months they are very active (between June and November). Noise may be heard in loft spaces and ceiling cavities, and they may be seen or heard in airing cupboards, cupboards and kitchens whilst out looking for food. Other indications will include gnawed wires, gnawed debris in roof spaces, fruit disappearing from trees, scratches on tree bark. Once fully emerged from hibernation they are very nimble and fast on their feet.

How to deal with a Glis Glis infestation?

Despite being regarded as a pest in the UK, the Wildlife and Countryside Act 1981 prohibits certain methods of killing dormice. This is because the Gliridae family of rodents is protected internationally under the Berne Convention on the Conservation of European Wildlife and Natural Habitats, to which the United Kingdom is a signatory. Removing edible dormice from a property may only be carried out by a qualified pest controller licensed by Natural England (Class licence CL02 to preserve public health and safety and prevent serious damage to crops).

If Glis Glis are suspected in a property the first step is to appoint a licensed Pest Controller to confirm the species is in fact Glis Glis, and not a different rodent, and identify areas of activity. Once their presence is confirmed specialist approved traps are required, passed for the use with these animals. Once all individual animals have been trapped only licensed contractors are allowed to remove and dispatch them in a humane way. Having trapped all the animals, it is then prudent to prevent reoccurrences by blocking access holes.

Because Glis Glis are regarded as pests, it is illegal for them to release them back into the wild and anyone attempting to control Glis Glis without a licence may be committing a criminal offence. The terms of Natural England licenses require the animals caught, to be killed by specific means – it is illegal to remove them and release them alive in another area. It is thought that some of the spread of Glis Glis to other areas has been caused by well-meaning householders who have trapped them, and then, out of a mistaken sense of humane disposal have released them. Not only is this illegal but all this does is present the problem to someone else.


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