As the nights stretch longer across Europe, one bat species is turning in early for the season. Researchers say Daubenton's bats are now hibernating a full month sooner than before, a surprising shift that could threaten their ability to make it through winter. 

What's happening?

Scientists at the University of Greifswald tracked more than 4,000 bats near Münster, Germany, using small ID tags to monitor when each entered and exited its hibernation site. Their findings show that while many animals are shortening their hibernation periods as temperatures rise, Dubenton's bats are doing the opposite, according to a news release.

Instead of waiting until late autumn, these bats are settling into hibernation up to four weeks earlier than they did 13 years ago. Even more concerning, they are not gaining additional fat to support the longer rest period, which could make survival increasingly difficult as seasonal patterns continue to change.

At the same time, another species, Natterer's bats, is adapting in the expected direction by shortening its hibernation as winters become milder.

"As temperatures are continuing to rise, the contrasting hibernation strategies could have a significant impact on the long-term survival of the species we studied," study co-lead author Frauke Meier said.

Why is this change in hibernation concerning?

"The results are of particular importance for nature conservation," Gabriella Krivek, the other lead author, said.

The timing shift is closely tied to food availability. Daubenton's bats feed primarily on aquatic insects that now hatch earlier in the year as water temperatures rise. By autumn, fewer insects remain, forcing the bats to enter hibernation. 

Younger bats are particularly vulnerable. "In their first year, they go to their hibernacula later than the adults. In the absence of food, this can contribute to an even lower chance of survival," says Krivek.

Bats are essential to both ecosystems and human life because they control insect populations that threaten crops and spread disease. A decline in their numbers could have ripple effects on agriculture and biodiversity.

What's being done to help the bat species?

In Germany, human access to bat hibernation sites is restricted from October through March to protect roosting colonies. Researchers say this period no longer covers the Daubenton's bats' extended hibernation, meaning protections need to be updated. 

Across Europe and North America, conservation efforts are stabilizing bat populations via safe roosting boxes, restored wetland habitats, and reduced pesticide use. These measures can strengthen bat populations and preserve the ecosystems that depend on them.

Do you think we still have a lot to learn from ancient cultures? Definitely 👍 Only on certain topics 👆 I'm not sure 🤷 No — not really 👎 Click your choice to see results and speak your mind.

Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet.