Forest Bats Forced to Find Shelter in Towns as Old Trees Disappear.

As forests lose their appeal as safe havens, certain bat species in Germany are turning to towns and villages for shelter. Among these is the Leisler’s bat (Nyctalus leisleri), a species traditionally dependent on old, hollow-bearing trees found in diverse forests. However, modern forestry practices have reduced the availability of such natural roosts, pushing these bats to seek refuge in urban areas and historic buildings like churches.

Researchers from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) have employed high-resolution GPS technology to track the movements of Leisler’s bats in unprecedented detail. Their study reveals how these bats navigate their habitats, which tree species they prefer when selecting roosting sites, and which forest environments they avoid. The findings were recently published in the Journal of Environmental Management.

Bats represent one of the most diverse mammal groups worldwide, with over 1,400 species. Many of Germany’s native bats, including the Leisler’s bat, thrive in structurally complex, deciduous forests rich in old trees and cavities. Yet, today’s forestry methods are changing these habitats, leading to a shortage of suitable tree hollows in plantation forests. This scarcity forces the bats to relocate their daytime resting places to human settlements, where they can find shelter in old trees, parks, and historic buildings.

Professor Christian Voigt of Leibniz-IZW and the University of Potsdam highlights the challenges faced by Leisler’s bats. “This species relies on diverse deciduous forests with many old trees featuring woodpecker holes,” he explains. “Such habitats are increasingly rare in the uniform pine plantations common in the study area in eastern Germany.” Although Leisler’s bats remain relatively common, their exact population size remains unknown.

For the study, 32 adult bats from Brandenburg were equipped with miniature GPS loggers, producing detailed data on their nightly foraging routes, daytime roosts, and commuting corridors. According to Dr. Carolin Scholz, a wildlife biologist at Leibniz-IZW, this data allowed the team to correlate bat movements with fine-scale forest composition, including individual tree species and small landscape elements such as hedges and tree rows.

Their analysis showed a clear preference for structurally rich oak forests, while bats tended to avoid spruce-dominated coniferous forests. Old oaks emerged as particularly important for roosting. Surprisingly, the data also revealed frequent use of urban environments, confirming that Leisler’s bats increasingly rely on alternative roosts in villages and towns.

Uwe Hoffmeister, a bat expert from the Office for Zoological and Botanical Consulting, adds, “GPS telemetry has shown that these bats are exploring village centers and historic buildings more than before. This shift likely stems from the loss of suitable roosting sites in intensively managed forests.”

The authors of the study stress the urgent need to protect these alternative roosts in settlements and call for more ecologically sustainable forestry. Practices such as selective timber harvesting and allowing longer growth periods can enhance structural diversity without severely impacting forestry economics. Urban green spaces also play a vital role as refuges for wildlife like bats.

“Protecting old, hollow-rich trees is essential not just in forests but also within urban landscapes,” Voigt emphasizes.

The study also raises concerns about wind turbines in forested areas, which pose an additional threat to Leisler’s bats. The bats are often killed by turbine blades, possibly because they mistake turbine silhouettes for large trees and fly toward them at dusk. This collision risk is significant since bats fly at rotor blade height.

To mitigate these dangers, the researchers urge that new wind turbines be sited away from structurally rich deciduous forests and known bat roosts.

By shedding light on the habitat preferences and movement patterns of Leisler’s bats, this research equips foresters, conservationists, and planners with vital information to implement effective protection measures. Preserving both natural and urban roosting sites alongside careful forest management will be key to ensuring the survival of these specialized forest bats in the years ahead. 

Source:https://phys.org/news/2025-05-forest-longer-home-refuge-settlements.html

This is non-financial/medical advice and made using AI so could be wrong.