For 21 winters, Britain’s loneliest bat hibernated in solitude within a disused railway tunnel in Sussex. This male greater mouse-eared bat (Myotis myotis) was thought to be the last of his kind in the country after being discovered in 2002—ten years after the species had been officially declared extinct in Britain.

Now, hope for the species’ return has emerged. A young, breeding-age female greater mouse-eared bat was recently found hibernating in the South Downs National Park.

“The finding of a female is rewarding and a remarkable discovery, which brings huge hope for this species,” said Daniel Whitby, an ecologist and founder of the Bat Conservation and Research Unit.

This marks the first confirmed sighting of a female of the species in Britain since the 1980s, offering a potential mate for the long-isolated male—if he returns to his former haunts.

A second individual, also a greater mouse-eared bat, has been discovered at Dover Castle, further raising hopes that the species may be quietly reestablishing itself. These bats, Britain’s largest species, are roughly the size of a small rabbit, with an impressive wingspan stretching nearly half a metre in flight.

The Sussex female has been carefully ringed for future identification. While it is unclear if she has bred, her discovery brings excitement to conservationists. The next question is whether the elderly male will return.

Since his initial discovery in 2002, he has consistently overwintered in his chosen tunnel, disappearing each summer to an unknown location before returning like clockwork. However, in 2019, he vanished, presumed dead—only to surprise his long-time observers by reappearing in both 2022 and 2023. Last winter, he was absent once again, leaving conservationists anxiously awaiting his return.

“It would be great if he turned up but he’s certainly getting on a bit,” said the ecologist Nick Gray of Sussex Bat Group. “The female is not an old bat so there’s every chance it has bred and will breed again in the future.”

Declared extinct in Britain in 1992, the greater mouse-eared bat was the first land mammal to disappear from the country since wolves vanished around 250 years earlier. However, shifting environmental conditions, including a warming climate and the spread of vineyards across southeast England, may be contributing to its unexpected resurgence.

In France, these bats are known to forage between grapevines, suggesting that similar habitats in Britain could now be supporting them.

Unlike many other bat species that catch insects mid-flight, the greater mouse-eared bat hunts differently. It swoops downward to seize grasshoppers, crickets, and dung beetles, often landing and using its wings to trap prey against the ground.

Conservation efforts are playing a role in supporting the species’ survival. The Vincent Wildlife Trust (VWT), with funding from Natural England’s species recovery team, is working to create and enhance roosting sites for Britain’s rarest bats, including the greater mouse-eared bat.

“The absence of the old male felt like the final nail in the coffin for this species in Britain, but this new discovery once again sparks hope that a mammal declared extinct could bounce back,” said Daniel Hargreaves, the bat programme manager for VWT. “The lonely male who hung around since 2002 hasn’t been seen since 2023 – but we can only hope further individuals are discovered and that a viable population is formed.

“By providing suitable roosts, restoring habitats and reducing anthropogenic threats such as artificial light and noise, this species might just stand a chance of recovering.”

Historically, the species was never common in Britain. When a colony was first discovered in 1957 on the Isle of Purbeck in Dorset, it caused a media sensation. Photos were published in The Times, and some bats were disturbed from hibernation to be filmed in television studios. Sadly, this interference led to fatalities, while others were taken by collectors, hastening the species’ decline.

The exact location of the newly discovered female remains undisclosed to protect the bats. The site hosts 11 species of hibernating bats, including the rare Alcathoe bat, one of Britain’s least-known species.

Gray added: “The site is undoubtably of national significance and we are so lucky to have it here within the South Downs national park.”