Bats: Masters of the Power Nap
- Andrew Scire
- Mar 22, 2023
- 3 min read
By: Andrew Scire
People tend to associate bats with vampires or monsters and while they can’t transform into Dracula, they do have some pretty interesting adaptations, especially with how they handle extreme temperatures. In order to save energy in extreme cold, bats utilize a strategy called torpor. In a sense, torpor is similar to hibernation in that an animal will reduce its metabolism and heart rate in order to save energy. Whereas hibernation can last months, torpor usually only lasts a few hours, almost like a power nap! Generally speaking, torpor is thought to be used by mammals in colder climates to save energy due to the high energetic cost of trying to stay warm but in recent years, the use of torpor in warmer climates has been a subject of interest. It’s hypothesized that because the energetic cost of flight is so high, bats will utilize torpor to save energy in a warm environment. Lara Keicher and her team, from the Max Planck Institute of Animal Behaviour, wanted to investigate whether or not the common noctule bat from temperate European climates would be able to use torpor in temperatures much warmer than they are used to. They also wanted to investigate whether or not that use differed between pregnant and non-pregnant bats.
In order to investigate whether or not the common noctule can use torpor at higher temperatures, Keicher and her team safely captured wild non-pregnant bats from populations in Southern Germany just before and immediately after their migratory period. They also captured wild female bats in early pregnancy from Eastern Poland to study. Bats were then safely transported to a research facility and placed in chambers with specialized equipment where the researchers could simultaneously monitor the body temperature, heart rate, and breathing rate as an indicator of metabolism for the bats across a wide range of external temperatures.
Once their experiments were completed, Keicher and her team discovered some interesting results. For one, the researchers found that at high ambient temperatures female bats exhibited a lower metabolic and heart rate, meaning they utilized torpor to save energy when the environment was hot. These results were found regardless of whether the bats were pregnant or not, meaning that regardless of reproductive status, female bats are able to use torpor to save energy across a wide range of temperatures. Interestingly, the researchers discovered that when exposed to temperatures that are closer to that of their natural environment, non-pregnant bats used torpor to save energy across the entire duration of the experiment (12 hours), but pregnant bats didn’t. Instead, many pregnant bats would use short bouts of torpor rather than using torpor for the duration of the experiment because staying in torpor for too long can negatively affect the development of their babies. While it was found that bats that rested for the entire duration of the experiment saved 93% of their daily energy expenditure, pregnant bats using short periods of torpor were still able to save 33% of their energy for the day!
In summation, the researchers found that regardless of reproductive status, pregnant bats can use torpor to save energy across a range of environmental temperatures. They also found that pregnant bats have adapted a few strategies to save energy while minimizing harm to their babies. The reason these results matter is that if bats can use torpor to save energy, even while pregnant, then there is a high chance that torpor use can help overcome the challenge of managing energy expenditure while pregnant and aid in the survival of mother bats and their young in a world that is growing ever warmer.
Commenti