How do bats find their babies? It may seem like a silly question but think about it: when a mother returns to the colony she must precisely identify her offspring among hundreds if not thousands of other specimens, all of whom are communicating with each other. And all this in complete darkness. Sure, bats have proverbially excellent hearing, but the question remains: how do they use it? A study by Doshisha University in Kyoto, published on Frontiers in Ethologynot only answers the question, but also reveals what happens to a mother bat, physiologically, when she has to find her children.
It’s not the first time for these bats
The study involved a colony of Alionoctula abramusa small East Asian bat that often establishes its roosts in man-made environments, especially roofs and attics. The colony in question lives a short distance from the Doshisha University campus, and has already “collaborated” with researchers in the past (albeit unintentionally). Some time before starting work on the newly published study, the Japanese team had tested the reaction of these bats to family separation by “kidnapping” a cub: only its biological mother abandoned the colony to look for it.
To investigate this interaction, the team took four pregnant females and placed them in a “laboratory colony.” The bats gave birth to three pups each, and scientists immediately recorded them isolation callsisolation calls, which work roughly like the crying of a newborn: they serve to attract the mother’s attention, and are therefore specific and “personalized” for each puppy. The rapid growth rate of the bats made it possible to study them until they reached maturity, or at least until they became independent from their mother: after 12 days the cubs stopped emitting isolation calls, and after 30 they began to sleep alone and not close to their mother, and they learned to emit “adult” calls (those were also recorded).
Mothers only hear their children
At this point, the researchers made the bat mothers listen to a series of calls: those of their children, but also those of other babies, mixed with the calls of an unknown adult, and listened to their hearts. They thus discovered that their heart rate increases when they hear the isolation call of their offspring, while it remains normal when faced with the call of someone else’s child; a reaction that continues to apply even when faced with the adult calls of their now former puppies.
It must be said that the call of the unknown adult also caused an increase in heartbeat in the bats: according to the authors, it means that their heart beats faster as a reaction to something, but it is impossible to say whether it is a positive or negative reaction by just looking at the electrocardiogram. The authors also underline that to have more precise results the sample would need to be enlarged: the study focused on only four mothers. Who knows if the Doshisha University colony agrees to continue contributing to the construction of this knowledge.
