The “Bats” of Friends, Individual Vocal Recognition in False Vampire Bats

If I were to blindfold you and take you into a room with two strangers and one of your friends, chances are you would be able pick out your friend from the others only hearing their voices. While this seems simple, there are actually two different cognitive processes that go into this ability. The first is recognition, using the unique characteristics of a voice to tell that it is the same, the second is discrimination, telling two different voices apart using these unique characteristics. These processes are generally conceptualized in a human centered context, but it turns out, other mammals just might exhibit similar processes, including the Indian False Vampire bat (Megaderma lyra) as shown in a 2013 experiment by Kastein, Winter, Kumar, Kandula, and Schmit. The anatomy of vocal call production mammals means any mammal that has a vocal call is capable of producing an individualized signal, and studies have shown many taxa to be able to perceive these individual signals, and change their behavior based on that perception. Bats are social mammals, and because they are most active at night and spend most of their time in the air, the most effective way for bats to communicate is vocally, which makes the cognitive processes of recognition and discrimination of individual vocal signatures all the more important for bats.

For the study, Kastein’s team used two groups of bats collected from two different locations in South India. The bats were observed to see how often individuals made physical contact to determine which pairs of bats had individual relationships. The researchers were interested in the bat’s “contact call” observed in solitary bats at a night roost. To record this call, they separated bats from their group, for up to four hours to create a situation that mimicked the natural conditions where contact calls are seen. The researchers then performed two different experiments using the recorded calls. For the first experiment, the experimental bat was played two different recordings, the first was always from a bat the experimental bat had an observed relationship with, while he other could be from a different bat that had also been seen in a physical contact relationship, a bat from the same group that had not been observed making contact with the experimental bat, or a bat from another group, and the bat’s response and the time taken to respond were observed. The second experiment the same call from a social partner was played repeatedly until the experimental bat did not respond to the call twice in a row, followed by a new recording from the same bat, a different social partner, or an unknown bat from the other group. For the first experiment, bats the bats responded similarly to all the calls they were played with no preference for social partners. The second experiment found that bats had a diminished response for a new call from the same bat as the other recordings compared to different individuals, but still responded to every new recording, suggesting that they were able to distinguish between the different calls, and recognize the original bat even if the call was different.

Recognizing individual vocal patterns as we think of it in humans, is a much more complex cognitive task than it seems, involving two different kinds of processing. These processes, particularly discrimination, can be difficult to conceptualize and show in non human mammals, but Kastien’s team showed that they can be observed in bats. This provides both an insight into he cognition of bats and a potential entry point to showing similar processes in other mammals.

Kastein, H., Winter, R., Vinoth Kumar, A., Kandula, S., & Schmidt, S. (2013). Perception of individuality in bat vocal communication: discrimination between, or recognition of, interaction partners? Animal Cognition, 16(6), 945–959. Retrieved from http://0-search.ebscohost.com.sophia.agnesscott.edu/login.aspx?direct=true&db=eoah&AN=31280154&site=pfi-live