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Zebra Finches Identify Individuals Using Vocal Signatures Unique to Each Call Type

Penelitian - Researchers show that distinct signatures differentiate zebra finch individuals for each call type. The distinctiveness of these signatures varies: contact calls bear strong individual signatures while calls used during aggressive encounters are less individualized.

Humans share the ability to recognize familiar individuals using vocal-cues with many other animal species that rely on individual-specific relationships, such as mated pair bonds, the mother−young bond, or the tolerance relationship developed by neighbor territorial animals.

Penelitian Zebra Finches Identify Individuals Using Vocal Signatures Unique to Each Call Type

Social animals also have complex vocal repertoires comprised of multiple call types that they use to communicate different behavioral states. Investigation of individual vocal recognition in animals, including humans, has demonstrated individual discrimination either in single-call types or in a few call types.

But yet, it is unknown whether individual recognition is present for an entire vocal repertoire or for humans, irrespective of the vocalization produced may it be laughing, speaking, shouting or whispering.

If vocal recognition was to exist throughout a repertoire, it would provide a unique opportunity to study the nature of the individual signature given the particular physical constrains of sound production and the ecological pressure to also produce distinctive multiple call types.

The percept of the human voice results in part from the combination of fundamental frequency modulations determined by the properties of the vocal source, and of specific spectral shaping by the vocal tract.

Individual information in animals could similarly be the result of morphological individual differences in the vocal apparatus that would cause similar passive shaping of the sound across all calls in one’s repertoire: the passive-voice-cues.

In support of that hypothesis, vocal tract resonances have been found to provide reliable cues to an individual’s identity in some calls of nonhuman mammals. Alternatively or in addition to passive-voice-cues, humans and animals can actively control their vocal organ not only to produce the different utterances or call types that carry different meanings.

But also to either exaggerate their voice features, active-voice-cues or to implicitly advertise one’s identity, signature cues. The nonexclusive passive-voice, active-voice, and signatures strategies have yet to be explored when studying individual recognition across a repertoire.

The zebra finch is a highly vocal social songbird that relies on a set of 11 call types to communicate different behavioral states, intents or needs. Because the coding of identity has been shown independently for some of these call types, it is a good model to investigate mechanisms of identity coding through a whole repertoire.

Julie Elie of the Helen Wills Neuroscience Institute at the UC Berkeley and colleagues using operant conditioning design to measure behavioral discriminability and acoustic analyses to determine the features that carry individual information.

“We perform a thorough comparison of individual signatures across the repertoire of the zebra finch. We find that zebra finches do not produce signatures that generalize across call types but instead generate call-type-specific individual signatures. The strength of this signature varies across call types and is stronger for social contact calls,” Elie said.

“Our behavioral experiments show that birds are able to discriminate the identity of vocalizers for all calls of the adult repertoires and for the two call types unique to juveniles. Birds are also able to identify a vocalizer irrespective of call type, a task that requires the memorization of a set of vocal signatures,” said Elie.

Journal : Julie E. Elie et al. Zebra finches identify individuals using vocal signatures unique to each call type, Nature Communications, 02 October 2018, DOI:10.1038/s41467-018-06394-9



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