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Rats have gotten a bad reputation over the years for being dirty, garbage-eating carriers of disease. But these ubiquitous rodents are also clever and capable of learning complex tasks, even using their imaginations to navigate in virtual reality.

Now, new research adds another odd skill to their résumés: hunting bats. In a new study published in the journal Global Ecology and Conservation, scientists describe the first-ever observations of brown rats snatching bats out of the air, then chowing down.

The novel behavior is a “remarkable” example of the rodents’ ability to make the most of their environment, the researchers write.

But it may also spell bad news: The two species could be exchanging pathogens—interactions that could eventually trickle down to affect human health—and the rats, which are not native to Germany, might be killing enough bats to harm the local populations.

“Our observations show how adaptable and skillful [brown] rats are in exploiting food resources in urban ecosystems, while highlighting a conservation issue linked to invasive mammals,” says lead author Florian Gloza-Rausch, a biologist at the Museum of Natural History in Berlin, in a statement. “To our knowledge, this type of rat behavior has not previously been documented scientifically.”

For the study, researchers focused on two major urban bat hibernation sites in northern Germany—one in the town of Bad Segeberg and the other in Lüneburg. The Bad Segeberg site, a cave located near a busy open-air theater, is used as a winter roost by more than 30,000 bats, mainly Daubenton’s bats (Myotis daubentonii) and Natterer’s bats (Myotis nattereri). The Lüneburg site, situated in a city park, consists of rock crevices used in the late summer and fall by swarms of Daubenton’s and Natterer’s bats, along with a handful of other Myotis species.

Scientists used infrared cameras and thermal imaging devices to investigate the sites during periods of high bat activity between 2020 and 2024. At the Bad Segeberg site, the camera captured crystal-clear footage of brown rats (Rattus norvegicus) hunting bats. They used two distinct strategies: Some of the rodents snuck up on stationary bats that had landed or were resting, while others pounced on bats as they flew through the air.

“Rats were frequently observed patrolling the landing platform at the cave entrance,” the researchers write in the paper. “They were standing upright on their hind legs, using their tails for balance and raising their forelegs to intercept flying bats. Individuals were documented capturing bats mid-air, killing them immediately with a bite and dragging them away.”

The kills occurred in the darkness of night. Rats have poor eyesight, so the scientists suspect the rodents detected the bats by feeling them with their whiskers or by sensing the air currents from the bats’ wings.

The camera at Bad Segeberg captured 30 predation attempts and 13 confirmed kills. There, the researchers also discovered the remains of at least 52 bats—including some that were not fully eaten, which suggests the rats stashed them away for later.

In Lüneburg, the researchers didn’t observe any kills directly. They did, however, see rats hanging around the park’s rock crevices and found a similar cache of bat carcasses, suggesting brown rats were probably hunting at that site, too.

To get a sense of how this hunting might affect local bat populations, the researchers ran some calculations. At Bad Segeberg, a single rat subsisting purely on bats—a worst-case scenario for the flying mammals—would need to eat around 140 total creatures, or one to two per day, over its three-month winter hibernation period to survive. Urban rat colonies, to use a conservative estimate, consist of 15 to 60 individuals, so that translates to between 2,100 and 8,400 dead bats in a given hibernation season. At a minimum, those assumptions mean 7 percent of the approximately 30,000 bats that overwinter there could be eaten.

Invasive rats can decimate native animal populations on islands. But the study indicates rodents may also have a similar effect in urban environments. The bats in Bad Segeberg and Lüneburg already face other threats to their survival, including light pollution and development. Now, it seems, they must also contend with hungry rats.

Threats to local bat populations aside, the scenario is also potentially risky for humans. The study did not investigate the transmission of diseases specifically, but the researchers point out that both bats and rats are known to carry a wide variety of pathogens. “Such interactions may facilitate the spillover of bat-associated pathogens to rodents, potentially altering disease dynamics and expanding transmission opportunities to humans and domestic animals,” the researchers write.

Against this backdrop, controlling invasive brown rat populations at key bat hibernation sites—such as by more effectively managing garbage and maintaining sewers—would be a win-win. Such efforts would “protect vulnerable bat populations and reduce potential public health risks” at the same time, says co-author Mirjam Knörnschild, a behavioral ecologist at the museum, in the statement.