Vocal learning (learning sounds by imitation) is central to human speech and language, but few animals are capable of it. “It has been difficult to study this trait in mammals since so few mammals display this ability, and those that do (whales, dolphins, seals, and elephants) cannot easily be used for neurobiological and genetic studies”, says MPI’s Ella Lattenkamp. According to Lattenkamp and her colleagues, an animal model is crucial for understanding the biology and evolution of vocal learning.
Together with senior researchers Sonja Vernes (Max Planck Institute for Psycholinguistics) and Lutz Wiegrebe (Ludwig Maximilians University), Lattenkamp decided to study the pale spear-nosed bat, a highly sociable animal with a rich repertoire of social calls. Would adult bats learn to imitate calls in a lab setting?
Mashed banana treat
Using a novel setup, the researchers trained six pale spear-nosed bats for four hours a day. The bats listened to a playback of calls with lower frequencies than their own calls. The animals were rewarded with a treat of mashed banana whenever they repeated the new calls correctly. After thirty days of training, all bats had started to lower the pitch of their calls. One bat even followed the playback and not just the reward schedule, which is particularly good evidence of auditory-guided vocal learning in this species of bat.
Disorders of speech and language
As bats are capable of vocal learning, the team will next explore how this is encoded in the bat brain using microscopic anatomy and neuroimaging techniques. “We have also sequenced this bats genome to identify genetic factors”, says Sonja Vernes. “Furthermore, we are designing gene manipulation studies that will look at the consequences of the knockdown of genes like FoxP2 on vocal learning in bats. In the long run this will shed light on human speech and language and may help us identify what goes wrong in genetic disorders of speech and language”.
Lattenkamp, E. Z., Vernes, S. C., & Wiegrebe, L. (2020). Vocal production learning in the pale spear-nosed bat, Phyllostomus discolor. Biology Letters, 16: 20190928. doi:10.1098/rsbl.2019.0928.