Glis glis, also known as the edible dormouse, is a nocturnal rodent that lives in just one small corner of Britain: the Chilterns countryside around Tring, where Walter Rothschild introduced it around 1902. It looks like a small grey squirrel, it loves lofts, and it is the one common loft pest you cannot legally trap yourself.
That last point catches homeowners out every year. The well-meaning plan of “catch it in a humane trap and let it go in the woods” is not just ineffective with glis glis. It is a criminal offence.
This guide explains what glis glis are, where they live, the damage they do, and exactly what the law allows when they move into your home.
Key takeaways
- Glis glis are edible dormice, introduced near Tring around 1902 and now numbering roughly 23,000 according to the Mammal Society’s 2018 estimate.
- Almost the entire British population lives within about 35 km of Tring, across the Hertfordshire, Bedfordshire and Buckinghamshire triangle.
- They gnaw cables, pipes and insulation, and a three-day Tring broadband outage in 2023 was blamed on a glis glis chewing a cable.
- Trapping glis glis without registering with Natural England is illegal, and releasing a captured one is a separate offence.
- Captured edible dormice must be humanely dispatched under the licence, so legal removal is a job for registered professionals.
What is a glis glis?
A glis glis, or edible dormouse, is a nocturnal rodent that looks like a small grey squirrel with a bushy tail. According to the Mammal Society, it is unusually long-lived for a rodent, averaging around nine years and reaching twelve, and it hibernates for roughly seven months of the year.
Glis glis are sociable animals. They live in loose colonies, hibernate communally and often share the same loft, which is why one set of scratching noises can turn out to be a dozen animals. Their breeding is tied to beech and oak seed years: young are born in August, usually in a single litter of around seven, and in poor seed years they may skip breeding entirely.
Because of the squirrel-like appearance, householders frequently report them as grey squirrels. If you are in the Chilterns area, it is worth checking before assuming you need squirrel control, because the law treats the two species completely differently.
Where in the UK are glis glis found?
Glis glis live almost entirely within about 35 km of Tring in Hertfordshire, across the Herts, Beds and Bucks triangle and the edges of Oxfordshire. The Mammal Society puts the population at approximately 23,000 as of 2018, roughly double the 1995 estimate and likely a conservative figure.
The whole population traces back to one release. According to Wildlife Online, Walter Rothschild introduced glis glis to Tring Park around 1902. They were prolific by the mid-1920s, with 39 caught at Pendley Manor near Tring in 1926, and had reached Bedfordshire and Buckinghamshire by the early 1930s.
What is striking is how little further they have travelled. A 2022 academic study confirmed that, after 120 years, this remains a slow invasion still centred on that original square of the home counties. Near the Chilterns, glis glis are a realistic loft suspect. Almost anywhere else in Britain, they are not.
Why are glis glis a problem in your loft?
Glis glis gnaw electrical cables, plastic water pipes and loft insulation, creating fire and flood risks. In August 2023, a three-day broadband outage across Tring was widely attributed to a glis glis chewing through a cable. At night they are loud, with scurrying, banging and squeaking carrying through ceilings from lofts and wall voids.
The damage list in homes is consistent:
- Stripped cable insulation, which is a genuine fire hazard.
- Gnawed plastic water pipes, with leak and flood risk.
- Shredded and soiled loft insulation, used for nesting and hibernation.
- Droppings and urine contaminating stored items and loft spaces.
- Persistent nocturnal noise that ruins sleep, often from several animals at once.
The problem is not confined to houses. The GB Non-Native Species Secretariat risk assessment identifies glis glis as a local forestry pest in high-density years through bark-stripping, and the government funds a dedicated Countryside Stewardship action, CSP20, for edible dormouse control and management.
Hearing noises in the loft in the Chilterns area? Book a free survey with JG Pest Control’s licensed glis glis specialists.
We are open every day except Christmas Day, early until late. Send us a message for a fast callback, or call the number at the top of this page.
Can you trap a glis glis yourself?
No. Edible dormice are listed on Schedule 6 of the Wildlife and Countryside Act 1981, so they cannot be trapped without a licence, and unlicensed DIY trapping is unlawful. Under the GOV.UK CL02 class licence, you must first apply to Natural England and receive written confirmation before setting a single trap.
Here is the part most homeowners do not expect. Under Schedule 9 and Section 14 of the same Act, it is also an offence to release a glis glis, or allow one to escape, into the wild. The CL02 licence states plainly that captured edible dormice cannot be released and must be humanely dispatched. The “humane catch and release” most people would instinctively try is itself a criminal offence.
The CL02 licence, which runs from 1 January 2026 to 31 December 2030, sets strict conditions even for those who are registered:
- Registration with Natural England first, with evidence of relevant experience or qualifications, and written confirmation before any trapping.
- Permitted methods only: appropriate live-capture traps, or spring traps approved under the Spring Traps Approval (England) Order 2018 set in tunnels.
- Traps must be inspected within 24 hours.
- Trapping is allowed only to preserve public health and safety, or to prevent serious damage to property, crops or timber.
- Annual returns must reach Natural England by 31 January, or the registration becomes void.
In short, there is no legal DIY route. The only lawful outcome for a trapped glis glis is humane dispatch by someone registered with Natural England to carry it out.
How do you get rid of glis glis legally?
The only legal route is professional removal by technicians registered with Natural England under the CL02 class licence. A proper treatment combines licensed trapping, with traps checked within 24 hours, humane dispatch as the licence requires, and proofing of entry points so a new colony cannot simply move back in.
This is exactly what JG Pest Control’s licensed glis glis removal service provides across the Chilterns and the wider home counties. Our RSPH (BPCA) Level 2 certified and trainee technicians are registered for this exact species, and we have been dealing with glis glis in Hertfordshire, Bedfordshire and Buckinghamshire lofts for 15+ years. We are rated 4.8 out of 5 on Trustpilot from more than 23,000 reviews.
A typical treatment looks like this:
- Survey of the loft, wall voids and exterior to confirm glis glis rather than squirrels or rats.
- Licensed trapping programme using approved traps, inspected within the legal 24-hour window.
- Humane dispatch of captured animals, as the CL02 licence requires.
- Proofing of gaps, eaves and entry holes to keep the colony from returning.
- Advice on overhanging branches and other access routes around the property.
Timing matters too. Glis glis hibernate from roughly October until April or May, so noise and trapping success peak between late spring and autumn. If you can hear them, the colony is active and that is the time to act.
Why are they called edible dormice?
The name comes from ancient Rome, where dormice were a delicacy. According to Atlas Obscura, the Romans fattened them in special terracotta jars called gliraria, feeding them walnuts and chestnuts before serving them at banquets. The “edible” label has followed the species ever since.
In modern Britain it is simply a protected, non-native loft invader with one of the strangest backstories of any UK pest: a Roman delicacy, released by a Victorian banker, now governed by one of the strictest trapping regimes in British pest control.
Frequently asked questions
Glis glis are not aggressive towards people, but they are a genuine hazard in a home. They gnaw electrical cables, which creates a fire risk, chew plastic water pipes and strip loft insulation. Their droppings and urine also contaminate loft spaces, so an established colony should be dealt with promptly.
No. Edible dormice are protected under Schedule 6 of the Wildlife and Countryside Act 1981, so trapping without a licence is unlawful. Releasing a captured one is also an offence under Schedule 9. Only people registered with Natural England under the CL02 class licence can trap them legally.
Glis glis are strictly nocturnal and surprisingly loud for their size. Householders typically report scurrying, thumping and banging overhead, along with distinctive squeaking and chattering. Because they live in loose colonies, the noise often sounds like several animals at once, and it usually starts shortly after dusk between spring and autumn.
Around seven months, typically from October until April or May, which is one of the longest hibernation periods of any mammal living in Britain. They often hibernate communally, and in houses they favour loft insulation and wall voids. A loft that goes quiet in winter does not mean the animals have left.
Almost all British glis glis live within about 35 kilometres of Tring, covering parts of Hertfordshire, Bedfordshire and Buckinghamshire and the edges of Oxfordshire. The population was estimated at around 23,000 in 2018, roughly double the 1995 figure, and the species has spread only slowly in 120 years.
Use a professional company whose technicians are registered with Natural England to trap edible dormice. They will survey the property, run a licensed trapping programme with traps checked within 24 hours, humanely dispatch captured animals as the licence requires, and proof entry points so the colony cannot return.
Glis glis in your loft? Get fully licensed, legal removal from the highest rated pest control company on Trustpilot.
We are open every day except Christmas Day, early until late. Send us a message for a fast callback, or call the number at the top of this page.