Dormouse numbers may be recovering after steep decline, survey suggests

Hazel dormouse numbers in England and Wales may have risen by almost 10% between 2020 and 2025, according to monitoring data, offering a tentative reversal after a steep long-term decline. Researchers caution that the estimate is uncertain and the population remains almost 60% below its 2000 level.

The National Dormouse Monitoring Programme, run by the conservation charity People’s Trust for Endangered Species, has tracked sites in England and Wales since 1998. Its data shows an average decline of 3.5% a year since 2000.

The apparent recent increase coincided with warmer, drier-than-average springs and summers. Researchers say warmer conditions may mean dormice spend less time in torpor — short periods of deep sleep — and have more opportunity to feed, breed and build reserves for winter. The data suggests a link in timing, but does not establish that warmer weather caused the rise.

The UK’s only dormouse species, the hazel dormouse, has disappeared from around 20 English counties and is now largely confined to southern England and parts of Wales. It depends on woodland and hedgerows, which have been lost across much of the countryside.

Survey co-author Ian White described the increase as “welcome good news” and grounds for “cautious optimism”, while stressing that numbers remain far below their 2000 level. Ecologist Charlotte Armitage said warmer summers may help dormice reproduce and raise more litters, but added that uncertainty remains over how the animals will respond to warmer, wetter winters.

Conservationists say protecting habitat and managing woodland remain essential. They also call for more research into how climate change will affect the species over the longer term.