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For the first time, brown rats have been filmed actively hunting bats, snatching some from the air and capturing others on the ground. The rodents were caught on camera at bat hibernation sites in northern Germany. According to a paper in the journal Global Ecology and Conservation, researchers believe this predation could be significant enough to threaten local bat populations.

This study is the first to systematically document brown rats hunting in urban Europe. Scientists set up infrared and thermal imaging cameras to monitor bats at two hibernation sites in the towns of Segeberg and Lüneburg-Kalkberg. Observations were made during peak bat activity over several months between 2020 and 2024.

The cameras revealed two distinct hunting strategies. Some rats stood upright, using their tails for balance as they grabbed the bats while they were flying. Others attacked them when they were resting on the ground. At the Segeberg site, the team recorded 13 confirmed kills over five weeks and found a cache of 52 bat carcasses. Similar remains and evidence of bat predation were also discovered at the Lüneburg-Kalkberg site.

The number of kills may not sound large, but the researchers calculated that even a small rat colony could kill up to 7% of the roughly 30,000 bats at the Segeberg site in a single winter. The attacks also occurred at a time when the bats were most vulnerable—during swarming and hibernation—meaning even limited predation could threaten the long-term survival of the population.

Rats are a well-known problem in many parts of the world, especially on islands where invasive species have wiped out large numbers of birds and bats. The study's authors say cities can create similar conditions, with wildlife concentrated in small areas, giving rats plenty of hunting opportunities.

"Our findings demonstrate that urban environments can replicate similar ecological dynamics [as islands], with invasive rodents exploiting high bat densities during critical life stages such as swarming and hibernation," wrote the researchers in their paper.

Conservation

The study highlights the importance of bat conservation strategies. The flying mammals help control insect populations and support healthy ecosystems by pollinating plants and dispersing seeds. But protecting bats is not only good for the environment; it also benefits human health, as the researchers point out.

"Management of invasive rodents at important bat hibernation sites supports biodiversity conservation and reduces potential public health impacts as part of a One Health strategy (an approach that considers the health of humans, animals and the environment together)."

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