What secrets are hidden in the babbling of bats?

Pups of the greater sac-winged bat have been recorded spending a significant part of their day making a curious chatter. This chatter, known as babbling, lasts around seven minutes on average, with some sessions reaching an impressive 43 minutes.

Researchers studied 19 pup-mother pairs in roosts across Panama and Costa Rica. According to Dr. Ahana A. Fernandez from the Smithsonian Tropical Research Institute, the project focused on how maternal behavior influences this vocal practice in young bats.

Bat pup babbling and infant speech

These tiny creatures produce many different syllable types during their babbling phase. Some of these sounds match up with calls that adults use for territorial defense and group identification.

Scientists use the term vocal ontogeny to describe how bat pups develop the full range of sounds that adults make. Babbling by greater sac-winged bats features repetitive and varied sequences that resemble early infant speech in humans.

Male bats sing loud territorial songs at dawn and dusk. Pup babbling, though, seems mostly linked to interactions with their mothers.

Maternal influence on bat babbling

Researchers filmed and recorded each babbling session. They noticed that some mothers stayed quiet, while others hovered, crawled, or moved closer to their pups during these long bouts of chatter.

Bat pups with more interactive mothers kept babbling longer. Those pups also showed a bigger variety of the learned song syllables in their practice.

Interestingly, the number of singing males in a roost did not matter for pup babbling length. Instead, the mother’s activity seemed to drive how long and how richly the pup practiced its sounds.

How feedback shapes learning

“Social interactions can have a direct effect on how baby talk develops,” concluded a study by Michael Goldstein and colleagues. In human babies, certain social responses can speed up the shift from simple babble to more mature sounds.

Bats may follow a similar pattern. Mothers often respond to babbling pups with touches, movements, or by allowing nursing right after a session.

Scientists suggest that these gestures reinforce the pup’s interest in babbling. The pups might then refine their vocal control more quickly through this extra practice.

Babbling beyond male tutors

Adult males offer a steady supply of acoustic input through their songs. Yet the presence of multiple singers in a colony does not appear to increase a pup’s babbling time.

Mothers, on the other hand, engage in direct interactions. The physical movements and close attention may push the pup to keep going, stacking more practice into each day.

This result differs from research in songbirds, where direct tutor interaction is often critical for learning. Bat pups instead appear to depend heavily on their mothers for motivation.

Why do female pups babble too?

Male bats use these songs later to mark territory. Females normally leave their birth colony once they are grown and do not sing these territorial tunes as adults.

Scientists were surprised to see no difference between male and female pups during babbling sessions. Both sexes copy adult song syllables, show similar levels of practice, and respond to their mothers in a similar way.

One idea is that female pups benefit from early song practice to identify local song dialects in new colonies. This extra experience might help them recognize males from their home group or pick suitable mates.

Mother’s moves and vocal maturity

Researchers also tracked whether pup syllables moved toward more adult-like features. They found that pups whose mothers showed higher activity reached mature-sounding syllables earlier.

These results could mean that the mechanical skills and brain processes for producing adult calls are boosted by social contact. Over time, the pup transitions from broad babbling to crisp, well-formed phrases.

Scientists have proposed that such maternal feedback helps the young strengthen vocal skills. Pups learn by comparing their own calls to the calls they hear, then adjusting until there is a match.

Connections to human speech

Though humans and bats are worlds apart, both rely on extensive vocal imitation in early life. People have long studied infant babbling to find clues about how children master speech.

Some researchers think that babbling might serve multiple goals. It gives the infant a chance to practice forming sounds, and it can trigger extra bonding time with caregivers.

Bats might display a comparable loop. Pups try out different notes, the mother replies with movement or attention, and the pup is encouraged to produce more complex sounds.

Long babbling sessions and complex learning

The final number of syllables mastered by weaning did not directly link to how active each mother was. That aspect might depend more on how long pups keep babbling or how quickly they pick up new sound types.

Future work could explore whether mothers respond more often to specific syllables. That level of detail may reveal patterns of back-and-forth shaping that were not obvious in the broader analysis.

Scientists also wonder if close contact with motherly affection can spark hormone changes in pups. This might influence how quickly babbling matures, echoing theories in human child development.

Significance of bat pup babbling

These findings hint at a social element in mammalian voice learning. Bats share certain brain structures with humans, making them especially interesting for understanding speech origins.

The study offers a glimpse into how complex communication systems can appear in non-human mammals. It also opens the door to new ideas on how maternal cues guide early vocal practice.

Such knowledge can enrich our understanding of communication in the animal kingdom. It might even offer fresh perspectives on how humans first learned to talk.

The study is published in the journal eLife.

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