Interesting Engineering reports that scientists from the Max Planck Institute for Animal Behavior (MPI-AB) and the University of Konstanz conducted a study to measure the heart rate of bats while flying in their natural habitat to understand their energy demands and survival strategies.
They attached ultra-small heart rate monitors weighing only 0.8 grams to several male noctule bats, which are common in Europe. The heart rate signals were recorded by a receiving device, and due to the limited range of detection, the researchers had to remain a few hundred meters close to the bat colony.
While flying, the heart rate of bats increases to 900 beats per minute (bpm).
PhD candidate Lara Keicher from the University of Konstanz stated that during the daytime, when the bats rest, measuring their heart rate posed no difficulties; however, at night, they fly great distances to hunt insects, sometimes up to several kilometers. Consequently, the research team had to follow them in a small plane. These foraging trips could last over an hour. Their efforts were rewarded with heart rate data throughout the long flights, revealing how bats manage their energy consumption throughout the day and across different seasons.
The heart rate of bats can reach up to 900 beats per minute (bpm) while flying – a rate so high that Keicher described it as “a high-pitched sound striking the ears.” However, this rapid heart rate is balanced by a strategy to reduce energy consumption.
One significant finding is that bats take advantage of “naps” in the spring. These short daytime sleep states allow them to decrease their heart rate to just 6 bpm, effectively conserving energy.
In the summer, male bats do not take these short naps. The warm weather leads to abundant food, prompting them to stay active throughout the day to generate sperm in preparation for mating with female bats.
Summer also sees bats being more active: they hunt for twice as long and consume more than in the spring. In one night, they can eat over 2,500 mosquitoes or 33 beetles.
This series of discoveries provides insights into the challenges bats face in energy consumption and how they cope with these challenges. Understanding this helps predict how bat populations will respond to significant temperature changes and food shortages caused by climate change, as well as supports conservation efforts for both pollinator and insect-eating species.
