A 21-year minitoring programme by hundreds of volunteers has been rewarded with tangible evidence that the endangered hazel dormouse (Muscardinus avellanarius) is showing signs of a comeback.

Data from the National Dormouse Monitoring Programme, organised by the People’s Trust for Endangered Species (PTES), shows that the decline in dormice had slowed to 9% between 2002 and 2008; when the project started in 1988, they were declining at a rate of 39% every year. Through the programme, which is funded by Natural England, there have been controlled releases of dormice, plus the provision of nesting boxes at about 200 sites there are 400 boxes in one wood on the Isle of Wight.

‘Although dormice are still a threatened species, the decline appears to be slowing down markedly,’ said PTES chief executive Jill Nelson. ‘It’s clearly too early to be totally confident about the animal’s long-term future, but we have reason to be optimistic that conservation efforts are repaying dividends.’

Despite these encouraging statistics, dormice are not home and dry. Loss of hedgerow habitat is the principal cause of dormouse decline, but they’re also vulnerable to climate changes, such as wetter springs and summers, and when warmer winters interrupt hibernation.

Dormice usually only breed once a year unlike other small mammals and a poor breeding year can have a drastic effect on population, hence the necessity for long-term monitoring. They currently number about 10,000 in the UK, compared to millions of fieldmice.