Researchers from Konstanz have achieved a groundbreaking feat: measuring the heart rate of bats in flight over several days in the wild.
This marks the first time such data has been collected for a bat species, providing new insights into the energy bats use daily and their strategies to conserve it.
The study, conducted by scientists from the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz, focused on male common noctule bats found throughout Europe.
The research aimed to understand how much energy bats consume and how their energy needs change throughout the year.
“Bats are fascinating animals that often share their habitat with us humans,” says Lara Keicher, the study’s lead author. “But there’s still so much we don’t know about them, like how much food they need and if they can find enough to survive different seasons.”
To understand bats’ energy requirements, especially as the climate changes, the researchers fitted bats with tiny heart rate transmitters weighing less than one gram.
These transmitters, which the bats wore for only a few days, sent out audio signals of their heartbeats. The scientists then recorded these signals using a radio receiver, which had to be within a few hundred meters of the bats to work.
“During the day, recording the heartbeats was easy because the bats were resting in tree caves or bat boxes,” says Keicher. She conducted this study as part of her doctoral thesis at the University of Konstanz and MPI-AB. “At night, however, the bats flew out to hunt insects, covering several kilometers quickly. To follow them during these nocturnal flights, we flew in a small airplane.”
The team, which included members from the Swiss Institute for Snow and Avalanche Research and the University of Freiburg, discovered that a bat’s heart rate could reach around 900 beats per minute during flight. To human ears, this sounded like a high-pitched tone. The recordings revealed fascinating energy-saving strategies that bats use during different seasons.
In spring, male common noctule bats enter a short daytime hibernation state known as “torpor,” where their heart rate drops to just six beats per minute. This helps them save energy when food is scarce. When they wake up, their heart rate quickly ramps up to 900 beats per minute within minutes.
In summer, however, the bats did not use torpor at all. Instead, they stayed awake during the day to invest energy in sperm production, preparing for mating in the autumn. To make up for this energy use, they hunted twice as long in summer compared to spring, eating up to 33 June beetles or over 2500 mosquitoes in one night.
The study’s findings, published in Proceedings of the Royal Society B, provide valuable insights into the energetic challenges bats face and their survival strategies. This knowledge will help predict how extreme temperature changes or food availability may impact these animals and potentially threaten their survival.
Dina Dechmann, the senior author of the study and a scientist at MPI-AB, emphasized the importance of this research. “All bat species are protected in Germany, and some are threatened with extinction. Basic research that investigates the behavior and adaptations of these animals can help us develop protective measures. This way, common noctule bats can continue to be seen in the night sky over Konstanz.”
This study not only highlights the resilience and adaptability of bats but also underscores the importance of understanding and protecting these mysterious creatures.
