Song hybridization events during revolutionary song change provide insights into cultural transmission in humpback whales

Cultural processes occur in a wide variety of animal taxa, from insects to cetaceans. The songs of humpback whales are one of the most striking examples of the transmission of a cultural trait and social learning in any nonhuman animal. To understand how songs are learned, we investigate rare cases of song hybridization, where parts of an existing song are spliced with a new one, likely before an individual totally adopts the new song. Song unit sequences were extracted from over 9,300 phrases recorded during two song revolutions across the South Pacific Ocean, allowing fine-scale analysis of composition and sequencing. In hybrid songs the current and new songs were spliced together in two specific ways: (i) singers placed a single hybrid phrase, in which content from both songs were combined, between the two song types when transitioning from one to the other, and/or (ii) singers spliced complete themes from the revolutionary song into the current song. Sequence analysis indicated that both processes were governed by structural similarity rules. Hybrid phrases or theme substitutions occurred at points in the songs where both songs contained “similar sounds arranged in a similar pattern.” Songs appear to be learned as segments (themes/phrase types), akin to birdsong and human language acquisition, and these can be combined in predictable ways if the underlying structural pattern is similar. These snapshots of song change provide insights into the mechanisms underlying song learning in humpback whales, and comparative perspectives on the evolution of human language and culture

Song hybridization events during revolutionary song change provide insights into cultural transmission in humpback whales

E.C.G. and this study were supported by a Newton International Fellowship from the Royal Society of London; L.L. was supported by Leverhulme Trust Research Project Grant RPG-2013-367; L.R. was supported by the Marine Alliance for Science and Technology for Scotland (MASTS) pooling initiative. MASTS is funded by the Scottish Funding Council (Grant HR09011) and contributing institutions. Song recordings in eastern Australia were funded by the Scott Foundation, the US Office of Naval Research, and the Australian Defence Science and Technology Organization. We thank everyone involved with this project. Some funding and logistical support was provided to M.M.P. by the US National Oceanic Society, Dolphin & Whale Watching Expeditions (French Polynesia), Vista Press, and the International Fund for Animal Welfare (via the South Pacific Whale Research Consortium).Cultural processes occur in a wide variety of animal taxa, from insects to cetaceans. The songs of humpback whales are one of the most striking examples of the transmission of a cultural trait and social learning in any nonhuman animal. To understand how songs are learned, we investigate rare cases of song hybridization, where parts of an existing song are spliced with a new one, likely before an individual totally adopts the new song. Song unit sequences were extracted from over 9,300 phrases recorded during two song revolutions across the South Pacific Ocean, allowing fine-scale analysis of composition and sequencing. In hybrid songs the current and new songs were spliced together in two specific ways: (i) singers placed a single hybrid phrase, in which content from both songs were combined, between the two song types when transitioning from one to the other, and/or (ii) singers spliced complete themes from the revolutionary song into the current song. Sequence analysis indicated that both processes were governed by structural similarity rules. Hybrid phrases or theme substitutions occurred at points in the songs where both songs contained “similar sounds arranged in a similar pattern.” Songs appear to be learned as segments (themes/phrase types), akin to birdsong and human language acquisition, and these can be combined in predictable ways if the underlying structural pattern is similar. These snapshots of song change provide insights into the mechanisms underlying song learning in humpback whales, and comparative perspectives on the evolution of human language and culture.PostprintPeer reviewe

Variability in humpback whale songs reveals how individuals can be distinctive when sharing a complex vocal display

Funding: L.L. was supported by a Leverhulme Trust Grant to L.R. (among other recipients; grant reference RPG-2013-367). L.R. was supported by the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. ECG was funded by a Royal Society Newton International Fellowship and a Royal Society University Research Fellowship. J.A.A. was funded by an Australian Government Research Training Programme Scholarship and the Australian American Association University of Queensland Fellowship. The HARC project was funded by the US Office of Naval Research, the Australian Defence Science and Technology Organisation, and the Australian Marine Mammal Centre.Individually distinctive acoustic signals in animal vocal communication are taxonomically widespread, however, the investigation of these signal types in marine mammals has focused only on a few species. Humpback whale songs are a stereotyped, hierarchically structured vocal display performed by males, and hence thought to be sexually selected. Within a population, whales conform to a common version of the song despite the song constantly evolving. While humpback songs have been studied extensively at the population level, individual level variation has been rarely described, with inconclusive results. Here we quantified inter- and intra-individual variability at different levels in the song hierarchy using songs from 25 singers across two song types from the eastern Australian population song of 2002 (12 singers), and the revolutionary song introduced in 2003 (13 singers). Inter- individual variability was found heterogeneously across all hierarchical levels of the song structure. In addition, distinct and individually specific patterns of song production were consistently recorded across song levels, with clear structural differences between the two song types. These results suggest that within the constraints of song conformity, males can produce individually distinctive patterns that could function as an advertisement to females to convey individual qualities.Publisher PDFPeer reviewe

Supplemental Material, Humpback-ABM-master - Using agent-based models to understand the role of individuals in the song evolution of humpback whales (<i>Megaptera novaeangliae</i>)

<p>Supplemental material, Humpback-ABM-master for Using agent-based models to understand the role of individuals in the song evolution of humpback whales (<i>Megaptera novaeangliae</i>) by Michael Mcloughlin, Luca Lamoni, Ellen C. Garland, Simon Ingram, Alexis Kirke, Michael J. Noad, Luke Rendell and Eduardo Miranda in Music & Science</p