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Vocal learning in a social mammal: Demonstrated by isolation and playback experiments in bats.

Prat Y, Taub M, Yovel Y - Sci Adv (2015)

Bottom Line: We continuously recorded pups from birth to adulthood and found that, when raised in a colony, pups acquired the adult repertoire, whereas when acoustically isolated, they exhibited underdeveloped vocalizations.Isolated pups that heard bat recordings exhibited a repertoire that replicated the playbacks they were exposed to.These findings demonstrate vocal learning in a social mammal, and suggest bats as a model for language acquisition.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.

ABSTRACT
The evolution of human language is shrouded in mystery as it is unparalleled in the animal kingdom. Whereas vocal learning is crucial for the development of speech in humans, it seems rare among nonhuman animals. Songbirds often serve as a model for vocal learning, but the lack of a mammalian model hinders our quest for the origin of this capability. We report the influence of both isolation and playback experiments on the vocal development of a mammal, the Egyptian fruit bat. We continuously recorded pups from birth to adulthood and found that, when raised in a colony, pups acquired the adult repertoire, whereas when acoustically isolated, they exhibited underdeveloped vocalizations. Isolated pups that heard bat recordings exhibited a repertoire that replicated the playbacks they were exposed to. These findings demonstrate vocal learning in a social mammal, and suggest bats as a model for language acquisition.

No MeSH data available.


Development of vocal diversity.(A) Three developmental stages of one pup from the control group (upper panels, blue) and one pup from the isolated group (lower panels, red), presented as a scatter plot of two acoustic features. Brown shades indicate these features’ distribution among adult calls. Insets in the right panels display representative spectrograms of vocalizations with different acoustic features. Note how the isolated pup is still using multiharmonic calls with a high fundamental even after the age of 140 days (undermost spectrogram). (B) Dispersion of the developing vocal repertoire, measured as the median absolute deviation (MAD) of the calls at every age in respect to these two features (see Supplementary Methods). Blue line, control group (n = 5); red line, isolated group (n = 5; n = 4 for the first two bins); dashed black line, the same measurement when applied to adults (n = 10); green dotted line, average of pups’ age on the assemblage day of pups-only groups. Error bars and shades, SEM.
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Figure 2: Development of vocal diversity.(A) Three developmental stages of one pup from the control group (upper panels, blue) and one pup from the isolated group (lower panels, red), presented as a scatter plot of two acoustic features. Brown shades indicate these features’ distribution among adult calls. Insets in the right panels display representative spectrograms of vocalizations with different acoustic features. Note how the isolated pup is still using multiharmonic calls with a high fundamental even after the age of 140 days (undermost spectrogram). (B) Dispersion of the developing vocal repertoire, measured as the median absolute deviation (MAD) of the calls at every age in respect to these two features (see Supplementary Methods). Blue line, control group (n = 5); red line, isolated group (n = 5; n = 4 for the first two bins); dashed black line, the same measurement when applied to adults (n = 10); green dotted line, average of pups’ age on the assemblage day of pups-only groups. Error bars and shades, SEM.

Mentions: To further illuminate the process in which bat vocal communication crystallizes, we examined how the variability among pup calls changes over time. Both pup groups assumed a highly diverse acoustical repertoire at a young age, much more diverse than that observed in the adults [Fig. 2, A (left panels) and B, and fig. S6]. As the control pups matured in the presence of vocalizing adults, their calls acoustically converged toward the adult vocal repertoire, and the huge diversity quickly disappeared (within ca. 3 months). However, the isolated pups kept their infantile diversity deep into their adolescence [Fig. 2, A (right panels) and B, and fig. S6]. Such extended vocal diversity among sub-adults has also been described in songbirds (15). These results demonstrate that isolated pups were capable of producing adult vocalizations, as they often did, but that they lacked the discriminatory mechanism (for example, adult guidance) that favors the adult-like acoustics.


Vocal learning in a social mammal: Demonstrated by isolation and playback experiments in bats.

Prat Y, Taub M, Yovel Y - Sci Adv (2015)

Development of vocal diversity.(A) Three developmental stages of one pup from the control group (upper panels, blue) and one pup from the isolated group (lower panels, red), presented as a scatter plot of two acoustic features. Brown shades indicate these features’ distribution among adult calls. Insets in the right panels display representative spectrograms of vocalizations with different acoustic features. Note how the isolated pup is still using multiharmonic calls with a high fundamental even after the age of 140 days (undermost spectrogram). (B) Dispersion of the developing vocal repertoire, measured as the median absolute deviation (MAD) of the calls at every age in respect to these two features (see Supplementary Methods). Blue line, control group (n = 5); red line, isolated group (n = 5; n = 4 for the first two bins); dashed black line, the same measurement when applied to adults (n = 10); green dotted line, average of pups’ age on the assemblage day of pups-only groups. Error bars and shades, SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643821&req=5

Figure 2: Development of vocal diversity.(A) Three developmental stages of one pup from the control group (upper panels, blue) and one pup from the isolated group (lower panels, red), presented as a scatter plot of two acoustic features. Brown shades indicate these features’ distribution among adult calls. Insets in the right panels display representative spectrograms of vocalizations with different acoustic features. Note how the isolated pup is still using multiharmonic calls with a high fundamental even after the age of 140 days (undermost spectrogram). (B) Dispersion of the developing vocal repertoire, measured as the median absolute deviation (MAD) of the calls at every age in respect to these two features (see Supplementary Methods). Blue line, control group (n = 5); red line, isolated group (n = 5; n = 4 for the first two bins); dashed black line, the same measurement when applied to adults (n = 10); green dotted line, average of pups’ age on the assemblage day of pups-only groups. Error bars and shades, SEM.
Mentions: To further illuminate the process in which bat vocal communication crystallizes, we examined how the variability among pup calls changes over time. Both pup groups assumed a highly diverse acoustical repertoire at a young age, much more diverse than that observed in the adults [Fig. 2, A (left panels) and B, and fig. S6]. As the control pups matured in the presence of vocalizing adults, their calls acoustically converged toward the adult vocal repertoire, and the huge diversity quickly disappeared (within ca. 3 months). However, the isolated pups kept their infantile diversity deep into their adolescence [Fig. 2, A (right panels) and B, and fig. S6]. Such extended vocal diversity among sub-adults has also been described in songbirds (15). These results demonstrate that isolated pups were capable of producing adult vocalizations, as they often did, but that they lacked the discriminatory mechanism (for example, adult guidance) that favors the adult-like acoustics.

Bottom Line: We continuously recorded pups from birth to adulthood and found that, when raised in a colony, pups acquired the adult repertoire, whereas when acoustically isolated, they exhibited underdeveloped vocalizations.Isolated pups that heard bat recordings exhibited a repertoire that replicated the playbacks they were exposed to.These findings demonstrate vocal learning in a social mammal, and suggest bats as a model for language acquisition.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.

ABSTRACT
The evolution of human language is shrouded in mystery as it is unparalleled in the animal kingdom. Whereas vocal learning is crucial for the development of speech in humans, it seems rare among nonhuman animals. Songbirds often serve as a model for vocal learning, but the lack of a mammalian model hinders our quest for the origin of this capability. We report the influence of both isolation and playback experiments on the vocal development of a mammal, the Egyptian fruit bat. We continuously recorded pups from birth to adulthood and found that, when raised in a colony, pups acquired the adult repertoire, whereas when acoustically isolated, they exhibited underdeveloped vocalizations. Isolated pups that heard bat recordings exhibited a repertoire that replicated the playbacks they were exposed to. These findings demonstrate vocal learning in a social mammal, and suggest bats as a model for language acquisition.

No MeSH data available.