Numbers of the hazel dormouse, otherwise known as the common dormouse, are dwindling.
Since the turn of the century, numbers of hazel dormice have decreased by more than a third up to 2016.
Experts believe the tiny mammal is under threat as a result of a loss of habitat, changes to how woodland and countryside are managed, and climate change.
Two cute hazel dormice in hibernation. After gathering up their fat reserves in autumn, hazel dormice will begin hibernation in winter. As the weather turns cooler they will move down from the trees to ground level, creating a tightly woven nest around the size of a tennis ball. They will curl up in this ball with their tail wrapped around their face and body to keep warm
Hazel dormice were once widespread in England and Wales, but have disappeared from 17 counties since Victorian times.
Now they are only commonly found in the South of England and areas of the English-Welsh border.
There are thought to be just 45,000 hazel dormice left in the country, down from about 60,000 16 years ago.
Numbers have fallen by 38 per cent since 2000, according to the State Of Britain’s Dormice report from the People’s Trust for Endangered Species (PTES).
The current rate of decline is equivalent to a fall of 55 per cent over 25 years, the report said.
The hazel dormouse lives at low densities and so would not be the main prey item of the garden dormouse.
‘Introduced grey squirrels are a much greater threat and are known to eat both young dormice and torpid adults,’ Hazel Ryans, senior conservation officer at Wildwood Trust told MailOnline.
‘Even our native yellow necked mice have been known to kill and eat the brains of hazel dormice.
‘[But] in some areas of Europe, eg Poland, the hazel dormouse and garden dormice are both native and coexist quite happily together.’
Hazel dormice can occasionally be spotted scampering across the countryside in search of food.
Agile climbers and mainly nocturnal, they’re very rarely seen.
They live in woodland, hedgerows and dense shrub and can spend their entire lives up in the branches without ever touching the ground.
The species eats buds, hazelnuts, berries and insects.
It builds summer nests of stripped honeysuckle bark in which the female will give birth to up to seven young.
They hibernate during the winter months, in a dense nest built in a tree cavity or similar, sheltered place, and curl up into a cute ball.
Dormice thrive in in shrubby habitat and brambles, and use hedgerows to move about the countryside.
One of the biggest threats to the tiny animals is a lack of management of woods, which is leaving trees unruly and isolated.
They have also been hit by more intensive agriculture, which has led to the loss of hedgerows and ‘flail cutting’ which reduces suitable habitat.
Ian White, dormouse officer at PTES said: ‘Woodlands in the landscape are becoming increasingly isolated. Dormice need the hedgerows to get around.
‘The problem within our fragmented landscape is where dormice have become locally extinct within a woodland, without a hedgerow network it is difficult for them to get back there.’
Mr White added that climate change was also having an impact on the mammals, which hibernate in winter.
Hazel dormice, their breeding sites and resting places are protected by UK law.
The UK government says: ‘You may be able to get a licence from Natural England if you can’t avoid disturbing them or damaging their habitats.’