Hazel dormice may be recovering in England and Wales after decades of decline, with new figures suggesting warmer summers are helping more of the animals survive.

Numbers up after long fall

The National Dormouse Monitoring Programme, led by the People's Trust for Endangered Species (PTES), has tracked dormice since 1998. It found numbers have fallen by almost 60% since 2000, an average decline of 3.5% a year.

More recent data points the other way. The population appears to have increased by almost 10% between 2020 and 2025, although researchers stress there is considerable uncertainty around that estimate.

Why warmer summers may help

The improvement coincides with warmer, drier-than-average springs and summers. Researchers believe the conditions may boost food supplies and reduce the time dormice spend in torpor, the short periods of deep sleep they enter when it is cold and wet or food is scarce, leaving them more energy for feeding and breeding.

Report co-author Ian White of PTES called the upturn "welcome good news" and grounds for "cautious optimism". But he added: "We mustn't lose sight of the bigger picture: populations remain almost 60% lower than they were in 2000."

Dr Charlotte Armitage, an ecologist who worked on the survey, said significant uncertainties remain, including how dormice will respond to warmer, wetter winters. "This is good news, but we can't be complacent," she told BBC News.

Still a rare and protected animal

The hazel dormouse is the only dormouse species in the UK. Once widespread, it is now largely confined to southern England and parts of Wales. It hibernates from around October to May in a nest on the ground. Conservationists say protecting woodlands and hedgerows remains essential to its long-term survival.