Bottlenose dolphin mothers modify signature whistles in the presence of their own calves

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Sayigh, Laela S.
El Haddad, Nicole
Tyack, Peter L.
Janik, Vincent M.
Jensen, Frants H.
Wells, Randall S.
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Animal communication
Signature whistle
Bottlenose dolphin
Vocal learning
Human caregivers interacting with children typically modify their speech in ways that promote attention, bonding and language acquisition. Although this “motherese,” or child-directed communication (CDC), occurs in a variety of human cultures, evidence among non-human species is very rare. We looked for its occurrence in a non-human mammalian species with long-term mother-offspring bonds that is capable of vocal production learning, the bottlenose dolphin (Tursiops truncatus). Dolphin signature whistles provide a unique opportunity to test for CDC in non-human animals, because we are able to quantify changes in the same vocalizations produced in the presence or absence of calves. We analyzed recordings made during brief catch-and-release events of wild bottlenose dolphins in waters near Sarasota Bay, Florida, USA, and found that females produced signature whistles with significantly higher maximum frequencies and wider frequency ranges when they were recorded with their own dependent calves vs. not with them. These differences align with the higher fundamental frequencies and wider pitch ranges seen in human CDC. Our results provide the first evidence in a non-human mammal for changes in the same vocalizations when produced in the presence vs. absence of offspring, and thus strongly support convergent evolution of motherese, or child-directed communication, in bottlenose dolphins. CDC may function to enhance attention, bonding and vocal learning in dolphin calves, as it does in human children. Our data add to the growing body of evidence that dolphins provide a powerful animal model for studying the evolution of vocal learning and language.
© The Author(s), 2023. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sayigh, L.S., El Haddad, N., Tyack, P. L., Janik, V.M., Wells, R. & Jensen, F.H., (2023). Bottlenose dolphin mothers modify signature whistles in the presence of their own calves. (Version 1) [Data set]. Woods Hole Oceanographic Institution, https://doi.or/10.26025/1912/66193.
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