Won’t be gone once the morning comes (Image: Dale Sutton/2020Vision/Corbis)

Defying years of shrinking habitat and disappearing roosts, bats are making a comeback in Europe.

Bat numbers – collected from 6000 hibernation sites in nine European countries – have increased by 43 per cent between 1993 and 2011, according to a new report by the European Environment Agency (EEA). The study, which tracks 16 of Europe’s 45 bat species, is the most comprehensive population study of bats on the continent to date.

“This trend is a definite sign of hope,” says Karen Haysom, director of science at the British Bat Conservation Trust, a partner in the study.


Armed with a statistical method that proved key in earlier EEA studies of European butterfly and bird population trends, Haysom and her collaborators input decades of national bat data into a dataset that revealed how bat numbers changed from winter to winter according to species and region. Never before had such data – reported by scientists and also by thousands of amateur bat enthusiasts, who counted hibernating animals in local caves and other roosts – been consolidated over such a broad time span and geography, Haysom says.

“This is giving us a chance to put our numbers in a different and very valuable context, and think about why some bat species are doing well in some countries compared with others,” she says. Population trends were calculated in Latvia, Hungary, The Netherlands, Austria, Portugal, Slovenia, Slovakia, Germany and the UK.

The bat-phone

In the second half of the 20th century, European bat populations plummeted due to increased agriculture, intentional killing, destruction of roosts and exposure to roofs treated with a pest-repellent called dieldrin. The decline was further fuelled by bats’ naturally long lifespan and slow reproduction rate, Haysom says.

But recent conservation efforts including cave protection, bat-friendly farming practices, local bat-assistance hotlines – bat-phones, if you will – and educational campaigns like local “bat walks” may have helped turn the tide.

The EEA team found that nine bat species, including Daubenton’s bat (Myotis daubentoni) and the Mediterranean horseshoe bat (Rhinolophus euryale) have increased, while several others held stable.

Citizen science

“Though the report is heartening, the job is certainly not done,” Haysom says. For instance, the grey long-eared bat (Plecotus austriacus) showed a continent-wide decline.

Bat specialist Paul Racey of the International Union for Conservation of Nature says the project demonstrates the power of citizen science in animal conservation efforts.

“To count butterflies or birds on a nice summer’s day is one thing, but counting bats hibernating in dark, damp, cold places – that’s a totally different ball game,” he says. “And yet, amazingly, thousands of volunteers and thousands of sites in Europe were committed to the work.”