Stereotypic and complex phrase types provide structural evidence for a multi-message display in humpback whales (<i>Megaptera novaeangliae</i>)

Murray, Anita; Dunlop, Rebecca A.; Noad, Michael J.; Goldizen, Anne W.

doi:10.1121/1.5023680

Cited by 19 publications

(22 citation statements)

References 70 publications

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“…300-500 hertz (Hz)), flat, tonal calls such as 'moans', 'groans', or 'cries', while one-way units covered the spectrum of acoustic features. The dominant use of stable one-way and diverse hourglass transitions reflects the combination of stereotypy and variability [8] which is observed in multiple levels of humpback whale songs [3,24]. The presence of these patterns across song variants and unrelated song types further suggests fixed roles in the song structure.…”

Section: Discussionmentioning

confidence: 99%

“…Qualitatively assigned themes were verified quantitatively using a weighted Levenshtein similarity index [24,30], with weightings (β = 1) based on acoustic similarity of units [29,31]. Hierarchical cluster analysis then grouped identified themes onto major dendrogram branches based on the similarity of their unit sequence patterns, confirming that theme assignments were robust.…”

Section: (B) Song Transcriptions and Theme Classificationsmentioning

confidence: 93%

“…Repertoire complexity (i.e. size and variety of sounds) has been quantified in humpback whale song [23], but quantitative studies are limited for structural complexity and syntactic rules [23][24][25][26]. In the current study, recordings of the east Australian humpback whale song were assessed over 13 consecutive years.…”

Section: Introductionmentioning

confidence: 99%

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Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song

et al. 2019

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Vocal communication systems have a set of rules that govern the arrangement of acoustic signals, broadly defined as ‘syntax’. However, there is a limited understanding of potentially shared or analogous rules across vocal displays in different taxa. Recent work on songbirds has investigated syntax using network-based modelling. This technique quantifies features such as connectivity (adjacent signals in a sequence) and recurring patterns. Here, we apply network-based modelling to the complex, hierarchically structured songs of humpback whales ( Megaptera novaeangliae ) from east Australia. Given the song's annual evolving pattern and the cultural conformity of males within a population, network modelling captured the patterns of multiple song types over 13 consecutive years. Song arrangements in each year displayed clear ‘small-world’ network structure, characterized by clusters of highly connected sounds. Transitions between these connected sounds further suggested a combination of both structural stability and variability. Small-world network structure within humpback songs may facilitate the characteristic and persistent vocal learning observed. Similar small-world structures and transition patterns are found in several birdsong displays, indicating common syntactic patterns among vocal learning in multiple taxa. Understanding the syntactic rules governing vocal displays in multiple, independently evolving lineages may indicate what rules or structural features are important to the evolution of complex communication, including human language.

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Section: Discussionmentioning

confidence: 99%

Section: (B) Song Transcriptions and Theme Classificationsmentioning

confidence: 93%

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Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song

et al. 2019

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“…An additional LSI analysis separated all phrases in each given year into 'phrase variants', representing slightly different arrangements of the same theme. Unique phrase variants were sung by a single individual, while shared phrase variants were sung by at least two individuals [25]. Data from 2006 (n ¼ 2 singers) and 2007 (n ¼ 1) were excluded to ensure a representative sample size per year [18,29].…”

Section: (D) Individualitymentioning

confidence: 99%

Cultural revolutions reduce complexity in the songs of humpback whales

et al. 2018

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Much evidence for non-human culture comes from vocally learned displays, such as the vocal dialects and song displays of birds and cetaceans. While many oscine birds use song complexity to assess male fitness, the role of complexity in humpback whale ( Megaptera novaeangliae ) song is uncertain owing to population-wide conformity to one song pattern. Although songs change gradually each year, the eastern Australian population also completely replaces their song every few years in cultural ‘revolutions’. Revolutions involve learning large amounts of novel material introduced from the Western Australian population. We examined two measures of song structure, complexity and entropy, in the eastern Australian population over 13 consecutive years. These measures aimed to identify the role of complexity and information content in the vocal learning processes of humpback whales. Complexity was quantified at two hierarchical levels: the entire sequence of individual sound ‘units’ and the stereotyped arrangements of units which comprise a ‘theme’. Complexity increased as songs evolved over time but decreased when revolutions occurred. No correlation between complexity and entropy estimates suggests that changes to complexity may represent embellishment to the song which could allow males to stand out amidst population-wide conformity. The consistent reduction in complexity during song revolutions suggests a potential limit to the social learning capacity of novel material in humpback whales.

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“…songs). For example, song variations in humpback whales have been used to investigate the function of song components in the context of inter-and intrasexual selection 9,10 , to examine population connectivity or group dynamics (e.g. [11][12][13] ), and to investigate mechanisms underpinning gradual song evolution and cultural revolution (e.g.…”

Section: Contribution To Unravel Variability In Bowhead Whale Songs Amentioning

confidence: 99%

Contribution to unravel variability in bowhead whale songs and better understand its ecological significance

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Schaar

Weissenberger

et al. 2021

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Since the first studies on bowhead whale singing behaviour, song variations have been consistently reported. However, there has been little discussion regarding variability in bowhead whale singing display and its ecological significance. Unlike the better studied humpback whales, bowhead whales do not appear to share songs at population level, but several studies have reported song sharing within clusters of animals. Over the winter season 2013–2014, in an unstudied wintering ground off Northeast Greenland, 13 song groups sharing similar hierarchical structure and units were identified. Unit types were assessed through multidimensional maps, showing well separated clusters corresponding to manually labelled units, and revealing the presence of unit subtypes. Units presented contrasting levels of variability over their acoustic parameters, suggesting that bowhead whales keep consistency in some units while using a continuum in values of frequency, duration and modulation parameters for other unit types. Those findings emphasise the need to account for variability in song analysis to better understand the behavioural ecology of this endangered species. Additionally, shifting from song toward units or phrase-based analysis, as it has been suggested for humpback whales, offers the opportunity to identify and track similarities in songs over temporal and geographical scales relevant to population monitoring.

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Stereotypic and complex phrase types provide structural evidence for a multi-message display in humpback whales (Megaptera novaeangliae)

Cited by 19 publications

References 70 publications

Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song

Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song

Cultural revolutions reduce complexity in the songs of humpback whales

Contribution to unravel variability in bowhead whale songs and better understand its ecological significance

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