In Germany, brown rats are hunting bats en masse

The rodents not only attacked weakened animals on the ground, but also intercepted them in the air during flight.

The study, published in the journal Global Ecology and Conservation, points to a real threat to bat populations, especially in urban environments where high animal densities make them more vulnerable.

A team of German biologists installed infrared and thermal imaging cameras at two urban bat wintering sites, in the cities of Bad Seegeberg and Lüneburg-Kalkberg. Over a period of several years (from 2020 to 2024), observations were made during the periods of highest colony activity.

The cameras recorded two hunting scenarios:

• Some rats stood up on their hind legs, balancing on their tails, and caught mice directly in the air;

• Others attacked mice resting or semi-paralysed from the cold on the ground.

One site recorded 13 confirmed kills in 5 weeks and found a cache of 52 bat carcasses. Similar signs of activity were also found in Lüneburg.

The researchers emphasise: if current behaviour is maintained, even a small colony of rats can kill up to 7% of the total wintering population of about 30,000 individuals. Mice are particularly vulnerable during periods of "swarming" behaviour and hibernation, when they are slow and unable to mount an active defence.

The scientific literature has long described how invasive species, especially rats, decimate bird and bat populations on islands that lack natural predators and high nesting densities. The authors of the new paper believe that urban environments can reproduce a similar ecological situation.

"Our data show that dense concentrations of animals and the absence of predators create ideal hunting conditions for rats, especially at critical times in the life cycle of bats," the paper notes.

Bats play a crucial role in ecosystems: they regulate the number of insects, pollinate plants and spread seeds. Their disappearance can upset the ecological balance.