The hazel dormouse (Muscardinus avellanarius) is a European Protected Species and is monitored by volunteers at sites in England and Wales for the National Dormouse Monitoring Programme.
But a recent analysis of figures from 400 UK sites between 1993 and 2014 found a dramatic 72 per cent decline in dormice over that period, amounting to a worrying annual rate of decline of 5.8 per cent.
Experts said the decline is ongoing and could mean that dormice are endangered in Britain, though the species is a top priority for conservation.
Cecily Goodwin, lead author of the Mammal Review study, said: “Dormice are declining despite strict protection and widespread efforts to conserve one of Britain’s most endearing woodland mammals.”
She said dormice live in woodlands, scrub and hedgerows, and eat flowers, nuts and insects.
They are nocturnal and often sleep for much of the day, enabling dormouse monitors to make careful counts.
Study senior author Prof Robbie McDonald added: “Dormice face a range of problems: climate change and habitat loss are likely to be important, but we think that appropriate woodland management could make a big difference.”
Dormice are very vulnerable to climatic changes, in particular wetter springs and summers, when foraging for food becomes harder and when warmer winter temperatures present them from successfully hibernating.
Unlike other small mammals who are able to breed prolifically, dormice usually have only one litter a year, sometimes two, which means that a poor breeding year can have a heavy impact on a population.