In 1992 greater mouse-eared bats (Myotis myotis) were declared extinct from the UK, but since 2002 a single male has been recorded hibernating in disused railway tunnels in West Sussex. He was officially known as ‘Britain’s rarest mammal’ and was assumed to have crossed the channel from France where there is an established population and taken up residence in Britain.

However, during this year’s National Bat Monitoring Programme in January 2023, members of Sussex Bat Group were astonished to find a second greater mouse-eared bat hibernating in this important network of tunnels.

Sheila Wright of the Sussex Bat Group says, “This is a hugely important discovery for the Sussex Bat Group and demonstrates the importance of regular monitoring of bat colonies – we could have missed this highly significant find of the second greater mouse-eared bat in Britain. It also shows how important it is to safeguard these hibernation sites for bats.”

Species recovery programmes are vital to mammal conservation efforts, required due to the threat from anthropological pressures in the 21st century such as roost loss, habitat loss and fragmentation. The Sussex Bat Group is working in partnership with Vincent Wildlife Trust (VWT) to restore the greater horseshoe bat (Rhinolophus ferrumequinum) range in Sussex, where it had been absent for more than 100 years. Like the greater mouse-eared bat, records of hibernating greater horseshoes were found in the network of disused railway tunnels, and eventually in 2019 a small pioneer breeding colony was identified in a stable block in West Sussex. VWT and Sussex Bat Group are working hard to raise funds to purchase the building, which was at risk of collapse, and rebuilding works are now underway to save the breeding roost whilst the bats are away hibernating. Find out more about this project.

Dr Stephanie Murphy of the Sussex Bat Group adds, ‘There are now many questions for us to answer: is there already a small pioneer population of greater mouse-eared bats recolonising Sussex and we just don’t know where they are breeding, as in the case of the greater horseshoe bat, or, as a result of climate change and the hottest summers on record in the UK, are we getting greater mouse-eared bats just beginning to move over from mainland Europe to settle in the UK?”

Greater mouse-eared bats are the largest of all British bats. They were to be found in Dorset and Sussex but had disappeared from both counties by around 1990. There are still colonies in northern Europe where they like large open roof spaces for their breeding colonies, overwintering in underground tunnels and caves. Their habitats include deciduous woodlands, meadows and pastures where they feed on large beetles, caterpillars, maybugs and crickets.

The greater horseshoe bat is one of the UK’s largest bats, about the size of a small pear. It gets its name from its fleshy nose that is shaped like a horseshoe. Formerly a cave-dweller, this bat now tends to roost in old houses, churches and barns, and hibernates over the winter in caves, disused mines, tunnels and cellars.