The longer record remains bleak. Since 2000, dormouse numbers have fallen by almost 60%, equivalent to an average annual decline of 3.5%. Populations remain almost 60% lower than in 2000, White noted, according to the BBC. The animals have become much rarer as large areas of woodland have been lost. Native populations have disappeared from around 20 English counties.
The data suggest the population increased by almost 10% between 2020 and 2025. Researchers stress there is considerable uncertainty around that estimate.
Hedgerows, another part of the habitat they depend on, have also been lost. That retreat of woodland and field boundaries has left the species far scarcer than it once was.
Even during spring and summer, dormice can enter short periods of deep sleep, known as torpor, when the weather is cold and wet, or when food is scarce.
The apparent rise coincided with warmer springs and summers. Scientists believe those conditions may help dormice survive by boosting food supplies and reducing the time they spend asleep.
The hazel dormouse is the only species of dormouse in the UK. It is famous for spending much of the year asleep.
Warmer summer conditions are likely to give the animals more energy to reproduce and raise additional litters, the research indicates.
Researchers believe warmer summers may be reducing the need for torpor. That would leave dormice with more energy for feeding and breeding.