ArticleLiterature Review

The multiple functions of male song within the humpback whale ( Megaptera novaeangliae ) mating system: review, evaluation, and synthesis: Humpback whale male song

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Abstract

Humpback whales (Megaptera novaeangliae) are seasonal breeders, annually migrating from high-latitude summer feeding grounds to low-latitude winter breeding grounds. The social matrix on the winter grounds is a loose network of interacting individuals and groups and notably includes lone males that produce long bouts of complex song that collectively yield an asynchronous chorus. Occasionally, a male will sing while accompanying other whales. Despite a wealth of knowledge about the social matrix, the full characterization of the mating system remains unresolved, without any firm consensus, as does the function of song within that system. Here, I consider and critically analyse three proposed functions of song that have received the most attention in the literature: female attraction to individual singers, determining or facilitating male–male interactions, and attracting females to a male aggregation within the context of a lekking system. Female attraction suggests that humpback song is an advertisement and invitation to females, but field observations and song playback studies reveal that female visits to individual singers are virtually absent. Other observations suggest instead that females might convey their presence to singers (or to other males) through the percussive sounds of flipper or tail slapping or possibly through vocalizations. There is some evidence for male–male interactions, both dominance and affiliative: visits to singers are almost always other lone males not singing at that time. The joiner may be seeking a coalition with the singer to engage cooperatively in attempts to obtain females, or may be seeking to disrupt the song or to affirm his dominance. Some observations support one or the other intent. However, other observations, in part based on the brevity of most pairings, suggest that the joiner is prospecting, seeking to determine whether the singer is accompanying a female, and if not soon departs. In the lekking hypothesis, the aggregation of vocalizing males on a winter ground and the visits there by non-maternal females apparently for mating meet the fundamental definition of a lekking system and its role though communal display in attracting females to the aggregation, although not to an individual singer. Communal singing is viewed as a form of by-product mutualism in which individuals benefit one another as incidental consequences of their own selfish actions. Possibly, communal singing may also act to stimulate female receptivity. Thus, there are both limitations and merit in all three proposals. Full consideration of song as serving multiple functions is therefore necessary to understand its role in the mating system and the forces acting on the evolution of song. I suggest that song may be the prime vector recruiting colonists to new winter grounds pioneered by vagrant males as population pressures increase or as former winter grounds become unavailable or undesirable, with such instances documented relatively recently. Speculatively, song may have evolved historically as an aggregating call during the dynamic ocean conditions and resulting habitat uncertainties in the late Miocene–early Pliocene epochs when Megaptera began to proliferate. Early song may have been comprised of simpler precursor sounds that through natural selection and ritualization evolved into complex song.

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... Various hypotheses on what drives baleen whale migration between such extremely spatially separated habitats have been put forward 2,3 , but to date, the reasons have not been understood entirely. On the breeding grounds, humpback whale sexual selection, copulation and parturition are presumed to take place [4][5][6] . Besides physical advertisement and intra/intersexual competition strategies (i.e., escorting of females and physical aggression among males) 4,6 , humpback whale males also perform acoustic displays in the form of songs 5,7 . ...
... On the breeding grounds, humpback whale sexual selection, copulation and parturition are presumed to take place [4][5][6] . Besides physical advertisement and intra/intersexual competition strategies (i.e., escorting of females and physical aggression among males) 4,6 , humpback whale males also perform acoustic displays in the form of songs 5,7 . Humpback whale song is speculated to fulfil a multi-purpose role within the species' mating system, in many aspects comparable to bird song 5,8 . ...
... Besides physical advertisement and intra/intersexual competition strategies (i.e., escorting of females and physical aggression among males) 4,6 , humpback whale males also perform acoustic displays in the form of songs 5,7 . Humpback whale song is speculated to fulfil a multi-purpose role within the species' mating system, in many aspects comparable to bird song 5,8 . The majority of songs are therefore produced on the low-latitude breeding grounds, but 'off-season' song has also repeatedly been recorded along migration routes and on feeding grounds during different times of the year alongside recordings of social and feeding sounds 7,[9][10][11][12][13][14][15][16] . ...
Article
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Humpback whale males are known to sing on their low-latitude breeding grounds, but it is well established that songs are also commonly produced ‘off-season’ on the feeding grounds or during migration. This opens exciting opportunities to investigate migratory aggregations, study humpback whale behavioral plasticity and potentially even assign individual singers to specific breeding grounds. In this study, we analyzed passive acoustic data from 13 recording positions and multiple years (2011–2018) within the Atlantic sector of the Southern Ocean (ASSO). Humpback whale song was detected at nine recording positions in five years. Most songs were recorded in May, austral fall, coinciding with the rapid increase in sea ice concentration at most recording positions. The spatio-temporal pattern in humpback whale singing activity on Southern Ocean feeding grounds is most likely shaped by local prey availability and humpback whale migratory strategies. Furthermore, the comparative analyses of song structures clearly show a differentiation of two song groups, of which one was solely recorded at the western edge of the ASSO and the other song group was recorded throughout the ASSO. This new finding suggests a common feeding ground occupation by multiple humpback whale populations in the ASSO, allowing for cultural and potentially even genetic exchange among populations.
... Songs last from 7 to 30 min (Frazer & Mercado, 2000;Payne & McVay, 1971) and occur more likely during the breeding season, could also be far more common during feeding season as previously thought (Stimpert et al., 2012). In most cases the singer is a male (Baker & Herman, 1984;Darling et al., 2006;Herman et al., 2013Herman et al., , 2017Smith et al., 2008). A humpback whale singer assumes a stationary behaviour at a depth of 8-30m and suspends itself into the water column, with a body longitudinal axis between 0°-75° from the vertical (Au et al., 2006;Frazer & Mercado, 2000). ...
... Another possible function which has been suggested for humpback whale song is to mediate interactions between males (Herman, 2017). Darling and Berube (2001) and Darling et al. (2006), showed that non singin males joined a male singer apparently to establish or affirm dominance, or to solicit an alliance between the joiner and the singer. ...
... Another possible function of humpback whale song as a secondary function of intrasexual advertisment is that females can hear singers within 100km distance and use songs to choose certain areas, while males might choose areas where to sing and avoid singers with more dominant voices (Frazer & Mercado, 2000). Furthermore, humpback whale breeding behaviour may function as a lek system, where song plays an important role in aggregating stimulus (Herman, 2017). Frazer and Mercado (2000) wondered how males might find females, since females generally avoid them and, apparently, they do not vocalize. ...
Thesis
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Humpback whales songs are thought to play an essential role in reproduction since the singing and reproductive periods coincide, and the singers are exclusively males. Humpback whale singers modify the composition and organisation of the song units over time. Previous studies suggested that such changes are gradual and occur at an ocean basin scale. In this study, the song of the humpback whale population breeding off Esmeraldas (Ecuador) was analysed to investigate its acoustic structure and the temporal variation over consecutive years. Data were collected as part of the CETACEA Project from 2013 to 2017 in the Galera - San Francisco Marine Reserve. The song units recorded during the five breeding seasons were classified into 14 vocal types based on visual inspection of spectrograms. In particular, using the TextGrid function in Praat, every single unit (N = 6076) was associated with a vocal type and saved as a separate .wav file. These song units were then analysed using an automated extraction of spectral coefficients (Linear Frequency Bins, LFB) which divided the song unit into ten portions of equal length and measured a set of 20 spectral coefficients between 50 Hz and 8000 Hz for each portion. The LFBs were used as dependent variables in a Principal Component Analysis, which transformed the original set of LFBs into 13 Principal Components (PCs) with an eigenvalue < 1. PCs were finally used in a series cross-validated (leave-one-out) Discriminant Function Analyses (DFA) to classify each unit according to its vocal type and year of emission. The results show that the acoustic structure of song units evolved over the study period, but that vocal types tend to be similar between consecutive years. Overall, this result provides further evidence that humpback whales songs change gradually over time. However, for the years 2015-2016 we observed that song units radically changed compared with the years 2013-2014 and 2016-2017. This study may constitute a starting point for further investigations. In particular, research effort should be direct toward the study of the vocal repertoire of neighbouring populations, in order to understand how the song transmission process happens.
... Nor is song exclusive to birds. While some characteristics remain contentious, most definitions now concede of its existence at least in bats (Smotherman et al., 2016), cetaceans (Herman, 2017), primates (Mitani & Marler, 1989;Clarke, Reichard & Zuberbühler, 2006), and mice (Holy & Guo, 2005;Pasch et al., 2011), while broader definitions may also include the songs of orthopterans, anurans, and other taxa (Greenfield, 2005;Stange & Ronacher, 2012). ...
... Song output is thus often used as an indicator of male quality in the most traditional sense -high song outputs require high energetic investment, meaning that the singers who produce them are generally in good condition, capable foragers, and able to defend territories against rivals (Gil & Gahr, 2002). Some studies, however, have challenged this, suggesting that song may be less energetically costly than previously thought (Oberweger & Goller, 2001;Ward, Lampe & Slater, 2004;Ilany et al., 2013;Herman, 2017). ...
... Courtship songs are produced by males across the taxonomic spectrum, including birds (Marler & Slabbekoorn, 2004;Catchpole & Slater, 2008), orthopterans (Zuk, 1987;Stange & Ronacher, 2012), anurans (Ryan, 1988), cetaceans (Herman, 2017) and bats (Bradbury, 1977;Behr & von Helversen, 2004;Davidson & Wilkinson, 2004;Bohn et al., 2009;Smotherman et al., 2016). Songs are known to convey information regarding attributes such as age and experience (Knörnschild et al., 2006(Knörnschild et al., , 2010, body size (Voigt et al., 2008;Hall et al., 2013;, dominance rank (Behr, von Helversen & Heckel, 2006), and even immunocompetence (Saino et al., 1997;Ryder & Siva-Jothy, 2000;Stange & Ronacher, 2012). ...
Thesis
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Short-tailed bats; Mystacina tuberculata; singing behaviour in bats; social organisation
... D calls are down sweeps that last several seconds and are considered a social call (McDonald et al. 2001, Oleson et al. 2007a, Lewis et al. 2018. Fin whales produce short (approximately 1 s duration), low-frequency calls known as 20 Hz calls (Watkins 1981), which are sometimes produced in long, patterned sequences that show geographic variation (Širović et al. 2009, 2017, Castellote et al. 2012, Helble et al. 2020. Humpback whales produce a variety of calls, ranging from 100 to 3000 Hz, which can be classified as song and non-song vocalizations (Payne and McVay 1971, Thompson et al. 1986, Dunlop et al. 2007, Stimpert et al. 2011, Fournet et al. 2015. ...
... Humpback whales produce a variety of calls, ranging from 100 to 3000 Hz, which can be classified as song and non-song vocalizations (Payne and McVay 1971, Thompson et al. 1986, Dunlop et al. 2007, Stimpert et al. 2011, Fournet et al. 2015. Song has been recorded only from males (Winn and Winn 1978, Tyack 1981, Baker and Herman 1984, Herman et al. 2013, Herman 2017 on both breeding and feeding grounds (Mattila et al. 1987, McSweeney et al. 1989, Gabriele and Frankel 2002, Clark and Clapham 2004, Vu et al. 2012. Predominant non-song call types in the North Pacific include growls and whups-low frequency (peak frequency < 150 Hz), short (1 s or less), and quiet calls, particularly relative to song (Wild and Gabriele 2014, Fournet et al. 2015, 2018. ...
... The echolocation clicks produced by sperm whales generally contain energy from 2 to 20 kHz, with the majority of energy between 10 and 15 kHz (Møhl et al. 2003). Risso's and Pacific whitesided dolphins produce broadband echolocation clicks that can be discriminated by their unique frequency banding patterns , Soldevilla et al. 2008, 2017. Beaked whale echolocation signals are unique in their polycyclic structure and FM pulse upsweep. ...
Article
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A variety of cetacean species inhabit the productive waters offshore of Washington State, USA. Although the general presence of many of these species has been documented in this region, our understanding of fine-scale habitat use is limited. Here, passive acoustic monitoring was used to investigate the spatial and temporal distributions of ten cetacean species at three locations offshore of Washington. Between 2004 and 2013, a total of 2845 days of recordings were collected from sites on the continental shelf and slope, and in a submarine canyon. Acoustic presence was higher for all species at sites farther offshore. Detections were highest during the fall and winter for blue ( Balaenoptera musculus ), fin ( B. physalus ), and humpback whales ( Megaptera novaeangliae ), likely related to reproductive behavior, while minke whales ( B. acutorostrata ) were only detected on two days. Odontocetes showed temporal separation, with sperm whale ( Physeter macrocephalus ) detections highest in spring, Risso’s ( Grampus griseus ) and Pacific white-sided dolphins ( Lagenorhynchus obliquidens ) highest in summer, and Stejneger’s beaked whales ( Mesoplodon stejnegeri ), Cuvier’s beaked whales ( Ziphius cavirostris ), and the BW37V signal type highest in winter or spring. There was interannual variation in detections for most mysticete species, which may be linked to oceanographic conditions: blue and fin whale detections increased during 2007 and 2008, and fin and humpback whale detections increased in 2011. These results inform our understanding of cetacean behavior and habitat use in this region and may aid in the development of conservation strategies suited to the dynamic conditions that drive cetacean distribution.
... A pesar de que el proceso de migración de las ballenas jorobadas ha sido bastante estudiado (Robbins et al. 2011;Stevick et al. 2011;Herman 2017;Albertson et al. 2018), aún se desconocen varios aspectos asociados a este comportamiento, como las distintas tasas de filopatría relacionadas con el género (Acevedo et al. 2006;Robbins et al. 2011;Stevick et al. 2011). Actualmente se presume que existe un flujo de individuos entre distintas poblaciones, que podría estar ocurriendo por la cercanía de áreas de alimentación y en algunos casos su solapamiento (Acevedo et al. 2006;Robbins et al. 2011). ...
... Existen varias hipótesis en relación con la función de estos cantos. Por un lado, se presume que el canto es un comportamiento intersexual, para atraer a las hembras, o intrasexual, como un despliegue de dominancia entre machos (Frankel 2009;Oña 2013;Herman 2017); también se piensa que los cantos son usados para la formación de una estrategia reproductiva tipo "lek" (Herman 2017), y como sonar para localizar hembras, diferenciar entre individuos y ubicarse en el entorno marino (Oña 2013). ...
... Existen varias hipótesis en relación con la función de estos cantos. Por un lado, se presume que el canto es un comportamiento intersexual, para atraer a las hembras, o intrasexual, como un despliegue de dominancia entre machos (Frankel 2009;Oña 2013;Herman 2017); también se piensa que los cantos son usados para la formación de una estrategia reproductiva tipo "lek" (Herman 2017), y como sonar para localizar hembras, diferenciar entre individuos y ubicarse en el entorno marino (Oña 2013). ...
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La descripción del canto de Megaptera novaeangliae, población Pacifico sudeste (stock G) en los años 2017 y 2018, detalló la estructura general e identificó su dinámica. Se analizaron cuatro grabaciones cada año, la mitad cuantitativamente, la otra mitad cualitativamente, las unidades del canto se midieron para utilizar herramientas estadísticas que confirmaran su clasificación. Se diferenciaron ocho unidades, seis y cinco para cada año, tres compartidas. El 2017 presentó ocho frases y el 2018 cinco. Cada año mostró una estructura general similar, tres temas, uno marcaba el comienzo y dos se intercalaban varias veces. Se comparó los espectrogramas con otros estudios de la misma población, la unidad C fue la más conservada por las frecuencias bajas y armónicos que le dan un mayor alcance; la H y F fueron también comunes, con amplitudes mayores, y la E con frecuencias altas, favorece su difusión en aguas poco profundas. La unidad C estaba presente en otras poblaciones. Esta información es un aporte importante para la comprensión de la especie y tiene implicaciones socioeconómicas y en su conservación.
... Although initially described as a "barnyard chorus" (Kibblewhite et al. 1967), scientists quickly came to view whale songs as the underwater analogues of bird songs (Payne et al. 1983;Winn and Winn 1978). As a result, most explanations for why humpback whales sing have focused on functions proposed for bird songs: attraction of mates and repulsion of competitors (Herman 2017). Underlying current hypotheses for the reproductive function(s) of humpback whale songs is the foundational assumption that singers combine sounds (called "units") into patterned sequences ("phrases" and "themes") to construct advertisement displays (songs) that can reveal the fitness of the singer to listening conspecifics. ...
... A final aim of the current study was to assess whether units vary along acoustic dimensions that affect how precisely listeners might localize the sources of units (or of echoes generated by units) from long distances. All current functional hypotheses for song function require that listening whales are able to track the locations of individual singers that cannot be seen (Herman 2017;Mercado 2018b), a task which can be quite challenging over long distances in shallow water environments (Frankel et al. 1995;Mercado and Frazer 1999;Mercado et al. 2007). Loud, sustained units that vary little in frequency over time will be highly detectable at long ranges, but may provide little information about the location of a singer (Barclay 1986;Simmons et al. 2014;Simmons and Stein 1980;Slabbekoorn et al. 2002). ...
... All of the recordings were made using a single hydrophone suspended from a boat. The singing humpback whales featured in these recordings are presumed to be adult males, because most identified singers to date have been found to be adult males (Herman, 2017). The recordings are most likely from different singers because there is no known exchange of individuals between Colombia and the West Indies, and because the probability of two singers recorded in different years being the same singer is low (Cerchio et al. 2001). ...
Article
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Flexible production and perception of vocalizations is linked to an impressive array of cognitive capacities including language acquisition by humans, song learning by birds, biosonar in bats, and vocal imitation by cetaceans. Here, we characterize a portion of the repertoire of one of the most impressive vocalizers in nature: the humpback whale. Qualitative and quantitative analyses of sounds (units) produced by humpback whales revealed that singers gradually morphed streams of units along multiple acoustic dimensions within songs, maintaining the continuity of spectral content across subjectively dissimilar unit “types.” Singers consistently produced some unit forms more frequently and intensely than others, suggesting that units are functionally heterogeneous. The precision with which singing humpback whales continuously adjusted the acoustic characteristics of units shows that they possess exquisite vocal control mechanisms and vocal flexibility beyond what is seen in most animals other than humans. The gradual morphing of units within songs that we observed is inconsistent with past claims that humpback whales construct songs from a fixed repertoire of discrete unit types. These findings challenge the results of past studies based on fixed-unit classification methods and argue for the development of new metrics for characterizing the graded structure of units. The specific vocal variations that singers produced suggest that humpback whale songs are unlikely to provide detailed information about a singer’s reproductive fitness, but can reveal the precise locations and movements of singers from long distances and may enhance the effectiveness of units as sonar signals.
... Feeding is rare or absent in winter breeding grounds, when most behaviours are related to calving and mating. The latter includes singing of long, complex song by male humpbacks to either attract females and/or meditate intrasexual interactions with other males (Payne and McVay, 1971;Clapham, 1996;Darling et al., 2006;Herman, 2017). ...
... Humpback whale social behaviour and demographics in the feeding areas and breeding grounds in the Northern Hemisphere, as well as along some migratory routes, have been well described (see summaries in Clapham, 1993Clapham, , 2000Herman, 2017). In contrast, there is relatively little understanding about the behaviours and demographics of humpback whales in so-called "stopover" habitats along migratory routes, to and from feeding areas and breeding grounds. ...
... These groups consist of a single female with or without a calf and two or more male escorts competing through various displays and aggressive acts for position and presumably potential mating access to the female (Tyack and Whitehead, 1983;Baker and Herman, 1984b;Clapham et al., 1992). Most non-agonistic social behaviour (described in detail below) in humpback whales in the breeding grounds or along migratory routes occurs in lone mothercalf pairs, in mother-calf pairs accompanied by a single escort (e.g., Craig et al., 2002Craig et al., , 2014Cartwright and Sullivan, 2009;Cartwright et al., 2012;Zoidis et al., 2014;Zoidis and Lomac-MacNair, 2017), in male-male dyads Darling and Berube, 2001;Darling et al., 2006), in male-female dyads (Jones, 2010;Herman et al., 2011;Pack et al., 2012) and among singers and whales that join them (Darling et al., 2006;Herman, 2017). ...
Article
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Agonistic competitive social behaviour in humpback whales [ Megaptera novaeangliae (Borowski, 1781)] has been extensively studied and reported in previous research. However, non-agonistic social behaviour in humpback whale pods has not been systematically studied. We investigated the social behaviour of 3,949 humpback whale pods over a period of 14 years during August, September, and October in Hervey Bay (Queensland, eastern Australia), a preferential female stopover early in the southern migration. Modelling and analyses of the data examined the factors influencing the occurrence and timing of non-agonistic social behaviour pods, agonistic competitive pods and newly associated pods. Non-agonistic social behaviour was observed more frequently during August when mature females, including early pregnant and resting females, co-occur and socially interact with immature males and females. Overall, relatively few mature males visit Hervey Bay. Agonistic competitive behaviour was observed with increasing frequency during September and October when mother-calf pods, with few escorts predominated. Mother-calf pods in Hervey Bay spent most of their time alone involved in maternal care. Agonistic competitive behaviour is related to the decreasing numbers of potentially oestrous females toward the end of the season. Non-agonistic social behaviour and agonistic competitive behaviour were more frequently observed in larger and newly associated pods. Overall, non-agonistic social behaviour pods were more prevalent than agonistic competitive social behaviour pods. The results of this study substantiate that non-agonistic social behaviour may be more prevalent than aggressive agonistic social behaviour in site-specific locations and habitats, depending upon the classes and timings of humpback whales using such habitats.
... Song unit social calls are detected most often in lone males and groups of multiple animals, and are likely only used by males (Dunlop et al., 2008;Rekdahl et al., 2013). Song itself is a reproductive display, although its primary function has not been established (Tyack, 1981;Darling and Bérubé, 2001;Herman, 2017;Murray et al., 2018). It has been proposed to possibly function in female attraction, whether to an individual or to an area, and/or by facilitating male-male interactions (Herman, 2017). ...
... Song itself is a reproductive display, although its primary function has not been established (Tyack, 1981;Darling and Bérubé, 2001;Herman, 2017;Murray et al., 2018). It has been proposed to possibly function in female attraction, whether to an individual or to an area, and/or by facilitating male-male interactions (Herman, 2017). In either case, information contained in the song is likely available to both sexes (Murray et al., 2018) and could be used by eavesdroppers as well as intended recipients . ...
... These sounds could contain similar information in whales during humpback whale competitive behavior. However, as low frequency, pulsive song units are also produced while singing, they may also be used to convey the same information (e.g., RHP) but in a different context, supporting the theory that song may serve multiple functions (Herman, 2017;Murray et al., 2018). Unfortunately, in the present study, the continuous background song precluded automated measurement of any acoustic features of the calls, or any quantitative classification of call types. ...
Article
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Intraspecific conflict can be costly; therefore, many species engage in ritualized contests composed of several stages. Each stage is typically characterized by different levels of aggression, arousal, and physical conflict. During these different levels of “intensity,” animals benefit from communicating potential information related to features such as resource holding potential, relative fighting ability, level of aggression, intent (i.e., fight or flight), and whether or not the competitor currently holds the resource (e.g., a receptive female). This information may be conveyed using both visual displays and a complex acoustic repertoire containing fixed (e.g., age, sex, and body size) and flexible information (e.g., motivation or arousal). Calls that contain fixed information are generally considered “discrete” or stereotyped, while calls that convey flexible information are more “graded,” existing along an acoustic continuum. The use of displays and calls, and the potential information they convey, is likely dependent on factors like intensity level. The breeding system of humpback whales (Megaptera novaeangliae) involves intense male competition for access to a relatively limited number of breeding females (the resource). Here, we investigated the behavior and acoustic repertoire of competitive groups of humpback whales to determine if an increase in intensity level of the group was correlated with an increase in the complexity of the vocal repertoire. We categorized the behavior of humpback whales in competitive groups into three mutually exclusive stages from low to high intensity. While discrete calls were infrequent compared to graded calls overall, their use was highest in “low” and “moderate” intensity groups, which may indicate that this stage of contest is important for assessing the relative resource holding potential of competitors. In contrast, visual displays, call rates, and the use of graded call types, were highest during “high intensity” competitive groups. This suggests that flexible information may be more important in “high intensity” levels as males continue to assess the motivation and intent of competitors while actively engaged in costly conflict. We have shown that the relatively complex social call repertoire and visual displays of humpback whales in competitive groups likely functions to mediate frequently changing within-group relationships.
... Researchers have argued that the primary factors leading to such changes are innovations produced by the most evolutionarily fit singers, or by copying errors that individual singers introduce (Garland & McGregor, 2020;Garland, Rendell, Lamoni, et al., 2017a;McLoughlin et al., 2016). This proposal derives from the widespread belief that the ultimate driver of variation in whale songs is sexual selection, especially female preferences for novelty (for review, see Herman, 2017). The main assumption underlying this belief is that female listeners will favor singers that "demonstrate conformity to the current version of the song as well as display innovation" (Cerchio et al., 2001, p. 326). ...
... Assessing the functional utility of humpback whale songs is logistically challenging. Correlating sound production with social contexts can potentially clarify how vocalizers are using sound (e.g., Clark, 1982), but this approach is often insufficient for resolving competing interpretations (Herman, 2017). In the case of bowhead whales, dynamic changes in vocal timing and frequency during navigation through ice are suggestive of echolocation, but might also be interpreted as social communication (Ellison et al., 1987). ...
... In reproductive contexts, male humpback whales may be limited to a strategy of searching for and "capturing" individual females (Clapham, 1996;Herman et al., 2011). Female humpbacks could encourage competitions either by making their presence known or by passing through areas where males are located (Clapham, 2000;Herman, 2017). Given that males are likely motivated to physically compete for access to a female, females may indirectly choose a mate based on his ability to consistently outcompete other males. ...
Article
Observations of animals’ vocal actions can provide important clues about how they communicate and about how they perceive and react to changing situations. Here, analyses of consecutive songs produced by singing humpback whales recorded off the coast of Hawaii revealed that singers constantly vary the acoustic qualities of their songs within prolonged song sessions. Unlike the progressive changes in song structure that singing humpback whales make across months and years, intra-individual acoustic variations within song sessions appear to be largely stochastic. Additionally, four sequentially produced song components (or “themes”) were each found to vary in unique ways. The most extensively used theme was highly variable in overall duration within and across song sessions, but varied relatively little in frequency content. In contrast, the remaining themes varied greatly in frequency content, but showed less variation in duration. Analyses of variations in the amount of time singers spent producing the four themes suggest that the mechanisms that determine when singers transition between themes may be comparable to those that control when terrestrial animals move their eyes to fixate on different positions as they examine visual scenes. The dynamic changes that individual whales make to songs within song sessions are counterproductive if songs serve mainly to provide conspecifics with indications of a singer’s fitness. Instead, within-session changes to the acoustic features of songs may serve to enhance a singer’s capacity to echoically detect, localize, and track conspecifics from long distances.
... The function of humpback whale song is not fully understood (Herman et al. 2013;Herman 2017), though its production is strongly linked to breeding behaviour (Payne and McVay 1971;Cerchio et al. 2001;Cholewiak 2008). Although song is extensively produced at breeding grounds, there are increasing reports of singing behaviour on low-latitude feeding grounds and during annual migrations when breeding is not observed (Gabriele and Frankel 2002;Clark and Clapham 2004;Vu et al. 2012;Garland et al. 2013;Gridley et al. 2018;Magnúsdóttir and Lim 2019). ...
... Signal to noise ratio (SNR) was visually assessed by the author (JH) and songs of low quality (i.e. units unclear or faint) were discounted from the detailed analysis section. Because songs can change in SNR over the song cycle, it is impractical to quantify the SNR for all units and visual assessment of SNR is typical in humpback song research (Cholewiak et al. 2013;Garland et al. 2015;Herman 2017). As can be seen by the sample sizes, we distilled the data to the best possible song sessions (six sessions out of 39 used) so that we could be confident in our results. ...
... In general, humpback whale song is very well studied (reviewed in Parsons et al. 2008;Herman 2017). In the South Pacific, for example, there have been extensive studies of the cultural transmission of song between different regional populations where some phrases were found to be common to all populations (Helweg et al. 1998;Garland et al. 2015). ...
Article
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Humpback whales are known for their complex and well-structured song that is typically produced on low-latitude breeding grounds. However, there is increasing evidence of song production on migration routes and high-latitude feeding grounds. Within a breeding ground and season, males share songs that progressively change over time. Song production on migration routes leads to the cultural transmission and sharing of songs. This is the first assessment of song structure in humpback whales recorded near Cape Town, South Africa. Song was identified in recordings made between 9 September 2016 and 21 October 2016 on a moored hydrophone located in Fish Hoek, False Bay. Thirty-nine song sessions were recorded, consisting of nine distinct units, forming ten themes. Themes occasionally overlapped in time, indicating multiple simultaneous singers. They were repeated on multiple days with consistent patterns in theme transition, demonstrating song sharing amongst individuals. Convergence on a similar song structure suggests singing whales originate from the same breeding stock. We propose that an unknown proportion of these whales continue to sing beyond the recognised breeding season. These data support previous studies that found that singing is not restricted to low-latitude breeding sites.
... Most species of marine mammals and cetaceans in particular are highly mobile, which may magnify the prominent benefit of using sounds to detect features in the marine environment. Indeed, cetaceans rely on acoustic signals for multiple biological functions: navigation and foraging (Miller et al., 2004), maintenance of social cohesion (Nousek et al., 2006;King et al., 2018), and reproduction (Herman, 2017) for instance. ...
... Humpback whales are the most vocal mysticetes (Payne and McVay, 1971). They produce two kinds of sounds: the song, a structured vocal display produced exclusively by males and mostly on the breeding grounds (Payne and McVay, 1971;Herman, 2017), but occasionally during migration and on the feeding grounds (Magnúsdóttir et al., 2014;Herman, 2017;Ryan et al., 2019; pers. obs.); and social sounds which include vocalisation and surface impacts with 53 flippers and body, produced by all individuals, including females and calves, all year round (Thompson et al., 1986;Dunlop et al., 2007;Stimpert et al., 2011;Rekdahl et al., 2013;Kavanagh et al., 2017). ...
... Humpback whales are the most vocal mysticetes (Payne and McVay, 1971). They produce two kinds of sounds: the song, a structured vocal display produced exclusively by males and mostly on the breeding grounds (Payne and McVay, 1971;Herman, 2017), but occasionally during migration and on the feeding grounds (Magnúsdóttir et al., 2014;Herman, 2017;Ryan et al., 2019; pers. obs.); and social sounds which include vocalisation and surface impacts with 53 flippers and body, produced by all individuals, including females and calves, all year round (Thompson et al., 1986;Dunlop et al., 2007;Stimpert et al., 2011;Rekdahl et al., 2013;Kavanagh et al., 2017). ...
Thesis
It is crucial for animals to use environmental stimuli to locate and evaluate the quality of resources and threats present in their surroundings. In the ocean, acoustic stimuli are privileged. Cetaceans are susceptible to detect acoustic stimuli produced by a multitude of sources, including other cetacean species and anthropogenic sources. I studied the behavioural responses of two cetacean species, the humpback whale and the long-finned pilot whale, to natural and anthropogenic acoustic stimuli (respectively killer whale sounds and naval sonars). I found that humpback whales were able to discriminate between the sounds of different killer whale ecotypes. I developed an unsupervised classification algorithm which takes into account the graded nature of animal vocalisations, and used this algorithm to describe the vocal responses of long-finned pilot whales to killer whale sounds and naval sonars.
... Notably, singers in a particular area change their songs in parallel, leading to the inference that singers are copying each other's songs. The driving force behind such copying is believed to be an acoustic competition that reveals a singer's reproductive fitness to other whales (Payne, 2000;Herman, 2017). In summary, the current consensus view about singing humpback whales is that all singers continuously and irreversibly, modify their song content throughout their adult lives, either by introducing new song elements or by copying new elements heard from other whales, so that they can maximize mating opportunities. ...
... While it is true that flexible social learning capacities can explain a wide range of complex social behaviors (Freeberg et al., 2012;Sewall, 2015), if cultural transmission becomes the default explanation for anything a singer does to change (or maintain) song characteristics, then it becomes a pseudoscientific explanation. Historically, the song-copying hypothesis has been attractive in part because it seems to tie the vocal ecology of humpback whales to that of other singing species like song-learning birds (Payne et al., 1983;Parsons et al., 2008;Herman, 2017;Cholewiak et al., 2018;Garland and McGregor, 2020). However, from the beginning, researchers have acknowledged that what whales are doing when they sing differs significantly in many ways from what singing birds are doing (Winn and Winn, 1978). ...
... Feminine fancies aside, there are likely proximate mechanisms that determine when a singer will produce longer or shorter song cycles (Chu and Harcourt, 1986;Miller et al., 2000;Fristrup et al., 2003), when they will skip or repeat themes (Frumhoff, 1983), and when they will morph phrase features, each of which can be experimentally and observationally investigated. For instance, if songs function collectively to act as a beacon for distant whales (Winn and Winn, 1978;Herman, 2017), then introducing multiple playbacks of current song around a targeted singer (at naturalistic distances) should have little effect on how the whale sings. Alternatively, if whales are adjusting their songs in response to the songs of their neighbors, then this intervention should have noticeable effects on the properties of the songs being produced (e.g., see Cholewiak et al., 2018). ...
Article
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Singing humpback whales (Megaptera noavaengliae) collectively and progressively change the sounds and patterns they produce within their songs throughout their lives. The dynamic modifications that humpback whales make to their songs are often cited as an impressive example of cultural transmission through vocal learning in a non-human. Some elements of song change challenge this interpretation, however, including: (1) singers often incrementally and progressively morph phrases within and across songs as time passes, with trajectories of change being comparable across multiple time scales; (2) acoustically isolated subpopulations singing similar songs morph the acoustic properties of songs in similar ways; and (3) complex sound patterns, including phrases, themes, and whole songs, recur across years and populations. These properties of song dynamics suggest that singing humpback whales may be modulating song features in response to local conditions and genetic predispositions rather than socially learning novel sound patterns by copying other singers. Experimental and observational tests of key predictions of these alternative hypotheses are critical to identifying how and why singing humpback whales constantly change their songs.
... Moreover, whaling data indicated that newly pregnant females were also present in the breeding areas (Dawbin, 1966;Nishiwaki, 1959Nishiwaki, , 1960Nishiwaki, , 1961. Although the breeding ecology of humpback whales is not fully understood, these various sources offer strong evidence that most mating behavior occurs in these breeding areas (Herman, 2017). ...
... Humpback whales produce long, complicated series of sounds, known as "songs" (Payne & McVay, 1971), mainly during their breeding season, but also during migration and sometimes towards the end of the feeding season (Herman, 2017;Mattila et al., 1987;Winn & Winn, 1978). The individuals producing songs are known as singers. ...
... Au et al. (2000) conducted 24 hr acoustic monitoring of singing behavior in Hawaii and reported that the sound pressure level (SPL) of songs was significantly higher at night than in the day, when the lowest value was observed between 1100 and 1500. In addition, studies have reported that singers are male noncalves of various levels of maturity (Herman et al., 2013), and while some may sing while escorting females including those with calf (Herman, 2017), most produce songs while they are alone, and stop singing with the interaction of other whales (Darling & Bérubé, 2001;Smith et al., 2008). Darling et al. (2006) also noted that lone singers are frequently joined by another lone male, though usually only for a short period of time. ...
Article
Male humpback whales produce complex sounds known as songs during their breeding season. Previous studies have shown diel patterns of song in their breeding areas, but there had been no similar studies in the breeding area around Okinawa, Japan. To study diel patterns of song and the behavior of humpback whales in Okinawa, we conducted 24 hr recording with a fixed hydrophone in 2007, and vessel‐based sighting surveys during 2014–2017. Song was monitored for 15 days, with peaks at sunrise and around 2200. Singing activity declined significantly between sunrise and sunset, then increased until 2200. Activity levels at night were higher and more stable than during the day. During 278 days of sighting surveys, 2,551 whales in 1,382 groups were observed. 79 individuals were confirmed as singers, all of which were lone whales. In six cases, singing individuals stopped singing before joining a group or began singing after leaving a group. Previous studies have shown that group size of humpback whales increases through the day. Considering the results from our study and the former studies, the decrease in singing activity as the day progresses may be a result of aggregation increasing, thus reducing the number of lone singers during the day.
... Although the precise function of humpback whale song still remains uncertain (Herman 2017;Darling et al. 2019), the structure of song has been well studied (Au et al. 2000;Parsons et al. 2008;Cholewiak et al. 2013). The first description of song was given by Payne and McVay (1971) where it was described as the structured repetition of sound features. ...
... The shortest continuous sound is termed a 'unit', several units sung together form a 'phrase', repeated phrases form a 'theme', and several distinct themes combine to form a 'song' (Payne and McVay 1971). Within a population and a time period, humpback whale males will converge on a song type (Sterelny 2009;Garland et al. 2011) through a process thought to be mediated by vocal production learning and cultural transmission (Janik 2009;Garland et al. 2013;Herman 2017). Therefore, inter-population variation in song patterns (Noad et al. 2000;Garland et al. 2011) is often present and can help identify separate populations or stocks (Darling et al. 2019). ...
Article
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Humpback whales (Megaptera novaeangliae) are highly vocal, producing a wide repertoire of sounds often organised into song. Song is prolific at breeding sites but also documented along migration routes and at feeding sites, including along the west coast of South Africa (28°–34°S). Here we examine the occurrence of humpback whale song within False Bay, South Africa, using intermittent recording periods from moored hydrophones spanning September 2016 to January 2018. Recordings from four locations were scrutinised for humpback whale vocalisations using long-term spectral averages (LTSAs). In total, 7205 h were examined, with song identified in 3% (211 h) of recording hours. Song was exclusively documented in September and October 2016 and was more prevalent at the most westerly sites. Diel patterns of song presence were modelled, showing the likelihood of detection was higher in the early morning and late evening (GAM: p < 0.05). On 15 occasions, two or more singers were detected with temporally overlapping song components. These results indicate prevalent, albeit seasonal, song production by humpback whales off the coast of South Africa and highlight the utility of passive acoustic monitoring to indicate their presence, behaviour, and potential population linkages in the region.
... Most marine mammals, and likely all cetaceans, rely on sound as their primary communication modality (Dunlop et al., 2007;Tyack, 2000). Humpback whales (Megaptera novaeangliae) are a highly vocal cetacean whose acoustic behavior is among the most well studied in the world (e.g., Herman, 2017;Payne & McVay, 1971). Song-a long, stereotyped, and repeated acoustic display thought to function primarily as a reproductive signal-is produced predominantly on breeding grounds and is sung only by males Cholewiak et al., 2013;Herman, 2017;Payne & McVay, 1971;Stimpert et al., 2012). ...
... Humpback whales (Megaptera novaeangliae) are a highly vocal cetacean whose acoustic behavior is among the most well studied in the world (e.g., Herman, 2017;Payne & McVay, 1971). Song-a long, stereotyped, and repeated acoustic display thought to function primarily as a reproductive signal-is produced predominantly on breeding grounds and is sung only by males Cholewiak et al., 2013;Herman, 2017;Payne & McVay, 1971;Stimpert et al., 2012). By contrast, "calls" (also known as "social sounds"; Silber, 1986), "social vocalizations" (Dunlop et al., 2007), "non-song calls" (Dunlop et al., 2008;Fournet et al., 2015;Stimpert et al., 2011) are used across the migratory corridor and in diverse social contexts (Cerchio & Dahlheim, 2001;Dunlop et al., 2008;Fournet et al., 2018a;Stimpert et al., 2007;Thompson et al., 1986), and are produced by males, females and calves (Dunlop et al., 2008;Mobley et al., 1988;Silber, 1986;Winn et al., 1979;Zoidis et al., 2008). ...
Article
Humpback whales (Megaptera novaeangliae) are a highly vocal baleen whale species with a diverse acoustic repertoire. “Song” has been well studied, while discrete “calls” have been described in a limited number of regions. We aimed to quantitatively describe calls from coastal Newfoundland, Canada, where foraging humpback whales aggregate during the summer. Recordings were made in July–August 2015 and 2016. Extracted calls were assigned to call types using aural/visual (AV) characteristics, and then agreement between quantitative acoustic parameters and qualitative call assignments was assessed using a supervised random forest (RF) analysis. The RF classified calls well (96% agreement) into three broad classes (high frequency (HF), low frequency (LF), pulsed (P)), but agreement for call types within classes was lower (LF: 63%; P: 85%; HF: 81%). We found support for a repertoire of 13 call types based on either high (≥70%) RF agreement (9 call types) or high (≥70%) AV agreement between two observers (4 call types). Five call types (swops, droplets, teepees, growls and whups) were qualitatively similar to call types from other regions. We propose that the variable classification agreement is reflective of the graded nature of humpback whale calls and present a gradation model to demonstrate the suggested continuum.
... They are known for their evolving vocal display called "song, " which is one of the most complex acoustic displays in the animal kingdom (Payne and McVay, 1971;Stimpert et al., 2012). Song is performed by males, predominantly on the breeding grounds (Stimpert et al., 2012), but also heard along migration routes and on the feeding grounds (Mattila et al., 1987;McSweeney et al., 1989;Clapham and Mattila, 1990;Clapham and Mead, 1999;Norris et al., 1999;Herman, 2017). Although the function of song is still a source of debate among experts, one possibility states that it could attract females to singers in a lekking arena or mediate interactions between males, making it particularly important for breeding functions (Herman, 2017). ...
... Song is performed by males, predominantly on the breeding grounds (Stimpert et al., 2012), but also heard along migration routes and on the feeding grounds (Mattila et al., 1987;McSweeney et al., 1989;Clapham and Mattila, 1990;Clapham and Mead, 1999;Norris et al., 1999;Herman, 2017). Although the function of song is still a source of debate among experts, one possibility states that it could attract females to singers in a lekking arena or mediate interactions between males, making it particularly important for breeding functions (Herman, 2017). ...
Article
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Soundscapes with minimal anthropogenic noise sources are key for the survival and effective communication of marine mammals. The Gulf of Tribugá is part of the breeding ground for humpback whale Stock G. Currently, no large-scale infrastructure exists on the Gulf's coastline, making it an area with high biodiversity and little anthropogenic noise. Whale-watching is one of the few human activities that contributes to the soundscape. By Morro Mico, on the southern limit of the Utría Natural National Park, an Ecological Acoustic Recorder (EAR, Oceanwide Science Institute) was deployed in the Gulf to record samples of acoustic activity from October to November 2018. It recorded for 10-min intervals with 20-min lapses for a duty cycle of 33.3%. One of the common peak frequencies of humpback whale song units from these recordings was used as input to an acoustic propagation model using the parabolic equation to simulate the communication space of a humpback whale when zero, one, and two boats are present. GPS positions of theodolite data from various whale watching scenarios in the Gulf were used to inform the models. Model results indicate that humpback whale song communication space could be reduced by as much as 63% in the presence of even one whale-watching boat. The boats traveling through the Gulf are the same as those used in whale-watching, and their engine noise while passing Morro Mico coincided with song structural and temporal changes observed in the acoustic data. Combining in situ data with acoustic models can advance the understanding of the spatio-temporal acoustic reactions of whales when their vocalizations are masked by boat noise. This project serves as an approximation of how humpback whale Stock G may respond to whale-watching vessel noise in the Gulf of Tribugá.
... Songs have only been recorded from male humpback whales (i.e., Glockner, 1983), and although the exact behavioral function is still debated, some of the hypotheses for the function of songs include male advertisement, mediating mate attraction, and/or male-male interactions (Cholewiak, Cerchio, et al., 2018;Herman, 2017;Smith et al., 2008). Humpback whale songs are generally recorded on tropical breeding grounds in winter (Darling et al., 2006;Payne & McVay, 1971), however, they have also been documented on feeding grounds outside of the traditional breeding season (Clark & Clapham, 2004;Garland et al., 2013;Magnúsdóttir et al., 2014;Mattila et al., 1987;Murray et al., 2014;Stimpert et al., 2012;Vu et al., 2012). ...
... Stimpert et al. (2012) suggested that song may be a more spatially and temporally plastic behavior than previously thought. Songs are characterized by a complex, repetitive, and hierarchically patterned structure (Herman, 2017;Payne & McVay, 1971;Tyack, 1983). These characteristics as well as the high source level (151-173 dB re 1μPa; Au et al., 2006) and long singing times (song sessions or bouts may continue for several hours; Payne & McVay, 1971) make song easily detectable and thus ideal for PAM detection methods. ...
... To that end, male humpback whales sing a long, complex, stereotyped, and hierarchically structured vocal sexual display termed "song" (Payne and McVay, 1971;Herman and Tavolga, 1980). It is generally agreed that song functions in sexual selection, but the details of whether its primary function is to attract a mate, mediate male-male interactions, or as a multi-message signal, are currently contested (see review by Herman, 2017). In terms of the comparative approach taken in this paper, both humpback whales and corn buntings are producing complex patterns that change over time; we compare the ways in which these patterns change. ...
... Humpback whales have a mating system that is polygynous, promiscuous (Clapham, 1996;Clapham and Palsbøll, 1997;Cerchio et al., 2005;, or a lek (including the "floating lek" proposed by Clapham, 1996). In a recent review of song function by Herman (2017), he concluded that humpbacks adhere to a classical lekking system (with a few additions), and the arena is at the scale of a breeding ground (e.g., over 1,000 km 2 ). In such a scenario, song changes are unlikely to radiate out from a center akin to corn buntings, as male humpbacks do not hold territories, rather they roam freely (along with females) on the breeding grounds. ...
Article
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Culture, defined as shared behavior or information within a community acquired through some form of social learning from conspecifics, is now suggested to act as a second inheritance system. Cultural processes are important in a wide variety of vertebrate species. Birdsong provides a classic example of cultural processes: cultural transmission, where changes in a shared song are learned from surrounding conspecifics, and cultural evolution, where the patterns of songs change through time. This form of cultural transmission of information has features that are different in speed and form from genetic transmission. More recently, culture, vocal traditions, and an extreme form of song evolution have been documented in cetaceans. Humpback whale song "revolutions," where the single population-wide shared song type is rapidly replaced by a new, novel song type introduced from a neighboring population, represents an extraordinary example of ocean basin-wide cultural transmission rivaled in its geographic extent only by humans. In this review, we examine the cultural evolutions and revolutions present in some birdsong and whale song, respectively. By taking a comparative approach to these cultural processes, we review the existing evidence to understand the similarities and differences for their patterns of expression and the underlying drivers, including anthropogenic influences, which may shape them. Finally, we encourage future studies to explore the role of innovation vs. production errors in song evolution, the fitness information present in song, and how human-induced changes in population sizes, trajectories, and migratory connections facilitating cultural transmission may be driving song revolutions.
... Humpback whales (Megaptera novaeangliae) are arguably the most extensively studied of the mysticetes (see summaries in Clapham, 2000Clapham, , 1996Gabriele et al., 2017;Herman, 2017;Herman et al., 2011). Yet, relatively little is known about variations in humpback whale stress physiology as compared to other parameters and life history traits, such as abundance, migratory trends, reproduction, behavior and communication (Allen et al., 2018;Baker et al., 1985;Barlow et al., 2011;Cartwright and Sullivan, 2009;Cates et al., 2019;Chittleborough, 1965;Cholewiak et al., 2018;Christiansen et al., 2016;Clapham et al., 1992;Clapham and Mayo, 1990;Craig et al., 2003Craig et al., , 2002Darling et al., 2006;Gabriele et al., 2007;Helweg and Herman, 1994;Pack et al., 2017;Tyack and Whitehead, 1983). ...
... On the breeding grounds all but suckling calves fast, and activities are largely devoted to calving, calf rearing, and mating, as well as to behaviors related to these activities. While on the breeding grounds, males produce long elaborate repeated vocal sequences termed "song" (reviewed in Herman, 2017) and also escort single females or single mother-calf pairs (Craig et al., 2002). When two or more males escort a female, the males compete for physical proximity (and presumably mating access) to that female (Clapham, 1996;Tyack and Whitehead, 1983). ...
... [11,20,73]), has proven remote PAM as very effective for the study of highly mobile marine mammal species in the Southern Ocean. The more detailed analysis of humpback whale acoustic recordings can provide further information on male singing behaviour, which is thought to a be a population-specific reproductive display [74,75]. ...
Article
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Southern Hemisphere humpback whales ( Megaptera novaeangliae ) inhabit a wide variety of ecosystems including both low- and high-latitude areas. Understanding the habitat selection of humpback whale populations is key for humpback whale stock management and general ecosystem management. In the Atlantic sector of the Southern Ocean ( ASSO ), the investigation of baleen whale distribution by sighting surveys is temporally restricted to the austral summer. The implementation of autonomous passive acoustic monitoring, in turn, allows the study of vocal baleen whales year-round. This study describes the results of analysing passive acoustic data spanning 12 recording positions throughout the ASSO applying a combination of automatic and manual analysis methods to register humpback whale acoustic activity. Humpback whales were present at nine recording positions with higher acoustic activities towards lower latitudes and the eastern and western edges of the ASSO . During all months, except December (the month with the fewest recordings), humpback whale acoustic activity was registered in the ASSO . The acoustic presence of humpback whales at various locations in the ASSO confirms previous observations that part of the population remains in high-latitude waters beyond austral summer, presumably to feed. The spatial and temporal extent of humpback whale presence in the ASSO suggests that this area may be used by multiple humpback whale breeding populations as a feeding ground.
... While the exact function of male song remains debated, there is consensus that it plays some function within the mating system of humpback whales (Winn & Winn 1978, Herman et al. 1980, Winn et al. 1981, Tyack 1983, Tyack & Whitehead 1983, Baker & Herman 1984, Darling & Bérubé 2001, Darling et al. 2006, 2012, Herman 2017, Cholewiak et al. 2018. Abating singing could indicate a shift in male focus towards other means of intra-sexual competition, such as physical combat , or it could be a direct reaction to lower numbers of receptive females. ...
Article
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Approximately half of the North Pacific humpback whale Megaptera novaeangliae stock visits the shallow waters of the main Hawaiian Islands seasonally. Within this breeding area, mature males produce an elaborate acoustic display known as song, which becomes the dominant source of ambient underwater sound between December and April. Following reports of unusually low whale numbers that began in 2015/16, we examined song chorusing recorded through long-term passive acoustic monitoring at 6 sites off Maui as a proxy for relative whale abundance between 2014 and 2019. Daily root-mean-square sound pressure levels (RMS SPLs) were calculated to compare variations in low-frequency acoustic energy (0-1.5 kHz). After 2014/15, the overall RMS SPLs decreased between 5.6 and 9.7 dB re 1 µPa ² during the peak of whale season (February and March), reducing ambient acoustic energy from chorusing by over 50%. This change in song levels co-occurred with a broad-scale oceanic heat wave in the northeast Pacific termed the ‘Blob,’ a major El Niño event in the North Pacific, and a warming period in the Pacific Decadal Oscillation cycle. Although it remains unclear whether our observations reflect a decrease in population size, a change in migration patterns, a shift in distribution to other areas, a change in the behavior of males, or some combination of these, our results indicate that continued monitoring and further studies of humpback whales throughout the North Pacific are warranted to better understand the fluctuations occurring in this recently recovered population and other populations that continue to be endangered or threatened.
... Humpback whales, for instance, produce long bouts of complex song that can last for hours primarily during the breeding season. It has been suggested that sexual selection is the main driver of the evolution of these elaborate signals (Herman, 2017;Janik, 2014). Toothed whales, however, do not appear to produce song to attract mates, but produce learned contact calls for recognition (e.g., signature whistles in bottlenose dolphins) (Sayigh et al., 2013). ...
Preprint
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Complex vocal learning, the capacity to imitate new sounds, underpins the evolution of animal vocal cultures and song dialects and is a key prerequisite for human speech and song. Due to its relevance for the understanding of cultural evolution and the biology and evolution of language and music, the trait has gained much scholarly attention. However, while we have seen tremendous progress with respect to our understanding of its morphological, neurological and genetic aspects, its peculiar phylogenetic distribution has remained elusive. Intriguingly, animals as distinct as hummingbirds and humpback whales share well-developed vocal learning capacity in common with humans, while this ability is quite limited in nonhuman primates. Yet, solving this ‘vocal learning conundrum’ may shed light on the constraints ancestral humans overcame to unleash their vocal capacities. To this end I consider major constraints and functions that have been proposed. I highlight an especially promising ecological constraint, namely the spatial dimensionality of the environment. Based on an informal comparative review, I suggest that complex vocal learning is associated with three-dimensional habitats such as air and water. I argue that this is consistent with recent theoretical advances – i.e., the coercion-avoidance and dimensionality hypotheses – and with the long-standing hypothesis that mate choice is a major driver of the origin and evolution of complex vocal learning. However, I stress that multiple functions may apply and that quantitative phylogenetic comparative methods should be employed to finally resolve the issue.
... The main evidence for communicative culture in humpback whales comes from how fast they can replace song elements as a group, with the main driver for change presumed to be trend-setting singers whose innovations go viral, along with occasional song-copying errors by less innovative singers (Allen et al., 2018;Garland, Rendell, Lamoni, et al., 2017;McLoughlin et al., 2018;Payne, 2000;Rekdahl et al., 2018). Researchers have speculated that by changing their songs over time, singers can better woo females (Herman, 2017;Parsons et al., 2008;Payne, 2000;Tyack, 1981), or bond with members of the local community (Darling et al., 2006). These hypotheses provide a plausible account for why humpback whales might change their songs, but have little to say about what qualities of songs whales should change or how. ...
Article
The complex songs produced by humpback whales have been cited as evidence of prodigious memory, innovativeness, sophisticated auditory scene analysis, vocal imitation, and even culture. Researchers believe humpbacks learn their songs culturally because songs appear to change rapidly, consistently, and irreversibly across whales within a population. Here, we present evidence of similarities in song structure both across populations and decades that strongly challenge claims that social learning is the main driver of variations in humpback whale songs over time. Groups of humpback whales that were not in acoustic contact (recorded in Puerto Rico in 1970, Hawaii in 2012, and Colombia in 2013-2019) produced songs in acoustically comparable cycles, suggesting that progression through sound patterns within and across songs is not simply determined by vocal imitation of innovative patterns, but may instead be controlled by production templates that prescribe how singers construct and transform songs over time. Identifying universal constraints on song production is critical to evaluating the role of vocal imitation and cultural transmission in the progressive changes that humpback whales make to their songs and for evaluating the functional relevance of such changes. The current findings illustrate how information theoretic analyses of vocal sequences can potentially obscure key acoustic qualities of signals that may be critical to understanding how vocalizers produce, perceive, and use those sequences. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
... The acoustic record logged by the Acousonde was manually scanned and the start and end points of individual song units (i.e., the smallest continuous segments comprising phrases and themes within a song; Au et al., 2006;Herman, 2017;Payne and McVay, 1971) were marked within a custom auditing script in MATLAB 2019a. Background song was rarely noted. ...
Article
Bio-logging devices are advancing the understanding of marine animal behavior, but linking sound production and behavior of individual baleen whales is still unreliable. Tag placement potentially within the near field of the sound source creates uncertainty about how tagged animal sounds will register on recorders. This study used data from a tagged singing humpback whale to evaluate this question of how sound levels present on a tag when calls are produced by a tagged animal. Root-mean-square (rms) received levels (RLs) of song units ranged from 112 to 164 dB re 1 μPa rms, with some, but not all, of the lower frequency units registering on the tag's 800 Hz accelerometer sensor. Fifty-nine percent of recorded units measured lower acoustic RLs than previously reported source levels for humpback song, but signal-to-noise ratios (SNRs) were 30–45 dB during periods of the dive with low noise. This research highlights that tag RL does not alone predict caller identity, argues for higher SNR thresholds if using SNR to inform decisions about the source of a call, and provides a baseline for future research identifying diagnostic properties of tagged animal calls in cetacean bioacoustic tag datasets.
... Also, in years with greater krill biomass, the duration of D calling was shorter, though not significantly (R 2 = 0.23, p = 0.16). The production of song by male humpback whales has been studied extensively, including on feeding grounds 42,43 , and proposed hypotheses regarding the purpose of these songs include intersexual and intrasexual functions 44 . While the production of B calls by male blue whales is likely associated with reproduction, their calling behavior is complex and, like humpback whale song, the precise functions are unknown 22 . ...
Article
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Blue whales need to time their migration from their breeding grounds to their feeding grounds to avoid missing peak prey abundances, but the cues they use for this are unknown. We examine migration timing (inferred from the local onset and cessation of blue whale calls recorded on seafloor-mounted hydrophones), environmental conditions (e.g., sea surface temperature anomalies and chlorophyll a), and prey (spring krill biomass from annual net tow surveys) during a 10 year period (2008–2017) in waters of the Southern California Region where blue whales feed in the summer. Colder sea surface temperature anomalies the previous season were correlated with greater krill biomass the following year, and earlier arrival by blue whales. Our results demonstrate a plastic response of blue whales to interannual variability and the importance of krill as a driving force behind migration timing. A decadal-scale increase in temperature due to climate change has led to blue whales extending their overall time in Southern California. By the end of our 10-year study, whales were arriving at the feeding grounds more than one month earlier, while their departure date did not change. Conservation strategies will need to account for increased anthropogenic threats resulting from longer times at the feeding grounds.
... Interestingly, the magnitude of spatial distancing observed here was greater for singers than for non-singing single adults. This suggests that maternal females may be more inclined to avoid associating with singers, as they frequently attract brief visits from nearby whales (mostly males) who are thought to be 'prospecting' for the presence of a female Herman 2017). As the number of escorts increases, so too does the potential for energetic and physical costs to the adult female-calf pair. ...
Thesis
Maternal humpback whales (Megaptera novaeangliae) face unique challenges during migration, as they must maintain contact with their calves while travelling long distances. This thesis quantified the vocal repertoire of female-calf pairs and established potential information contained within their calls; provides robust baseline information on the size of their communication space; examined how their vocal activity is affected by behavioural state; and determined whether they modify their calling and/or migratory movement behaviour in response to their social environment. These results have increased our understanding of female-calf communication strategies under natural noise conditions, providing a foundation to explore how anthropogenic noise may affect them in the future.
... Humpback whales, for instance, produce long bouts of complex song that can last for hours primarily during the breeding season. It has been suggested that sexual selection is the main driver of the evolution of these elaborate signals (Herman 2017;Janik 2014). Toothed whales, however, do not appear to produce song to attract mates, but produce learned contact calls for recognition (e.g., signature whistles in bottlenose dolphins) (Sayigh et al. 2013). ...
Article
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Complex vocal learning, the capacity to imitate new sounds, underpins the evolution of animal vocal cultures and song dialects and is a key prerequisite for human speech and song. Due to its relevance for the understanding of cultural evolution and the biology and evolution of language and music, the trait has gained much scholarly attention. However, while we have seen tremendous progress with respect to our understanding of its morphological, neurological and genetic aspects, its peculiar phylogenetic distribution has remained elusive. Intriguingly, animals as distinct as hummingbirds and humpback whales share well-developed vocal learning capacity in common with humans, while this ability is quite limited in nonhuman primates. Yet, solving this ‘vocal learning conundrum’ may shed light on the constraints ancestral humans overcame to unleash their vocal capacities. To this end I consider major constraints and functions that have been proposed. I highlight an especially promising ecological constraint, namely the spatial dimensionality of the environment. Based on an informal comparative review, I suggest that complex vocal learning is associated with three-dimensional habitats such as air and water. I argue that this is consistent with recent theoretical advances—i.e., the coercion-avoidance and dimensionality hypotheses—and with the long-standing hypothesis that mate choice is a major driver of the evolution and origin of complex vocal learning. However, I stress that multiple functions may apply and that quantitative phylogenetic comparative methods should be employed to finally resolve the issue.
... These areas could be acoustically more suitable for singing males because they may be quieter than the surrounding pelagic environment and provide better sound propagation toward the open water 75 . As songs are likely to play a role in the spatial aggregation of individuals 76,77 , seamounts visited by great numbers of humpback whales could be acoustically attractive. ...
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Humpback whales (Megaptera novaeangliae) are known for their nearshore distribution during the breeding season, but their pelagic habitat use patterns remain mostly unexplored. From 2016 to 2018, 18 humpback whales were equipped with depth-recording satellite tags (SPLASH10) to shed light on environmental and social drivers of seamount association around New Caledonia in the western South Pacific. Movement paths were spatially structured around shallow seamounts (<200 m). Indeed, two males stopped over the Lord Howe seamount chain during the first-ever recorded longitudinal transit between New Caledonia and the east coast of Australia. Residence time significantly increased with proximity to shallow seamounts, while dive depth increased in the vicinity of seafloor ridges. Most of the 7,986 recorded dives occurred above 80 m (88.5%), but deep dives (>80 m, max 616 m) were also recorded (11.5%), including by maternal females. Deep dives often occurred in series and were characterized by U-shapes suggesting high energy expenditure. This study provides new insights into the formerly overlooked use of pelagic habitats by humpback whales during the breeding season. Given increasing anthropogenic threats on deep sea habitats worldwide, this work has implications for the conservation of vulnerable marine ecosystems.
... Barrett-Lennard et al. 1996, Miller et al. 2004, breeding (e.g. Smith et al. 2008, Herman 2017, and social coordination (e.g. Nousek et al. 2006, Jensen et al. 2011, Gero et al. 2016, King et al. 2018). ...
Article
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Eavesdropping, the detection of communication signals by unintended receivers, can be beneficial in predator-prey interactions, competition, and cooperation. The cosmopolitan killer whale Orcinus orca has diverged into several ecotypes which exhibit specialised diets and different vocal behaviours. These ecotypes have diverse ecological relationships with other marine mammal species, and sound could be a reliable sensory modality for eavesdroppers to discriminate between ecotypes and thereby respond adaptively. Here, we tested whether humpback whales Megaptera novaeangliae in the Northeast Atlantic responded differently to playback of the sounds of 2 killer whale ecotypes, Northeast Atlantic herring-feeding killer whales representing food competitors and Northeast Pacific mammal-eating killer whales simulating potential predators. We used animal-borne tags and surface visual observations to monitor the behaviour of humpback whales throughout the playback experiments. Humpback whales clearly approached the source of herring-feeding killer whale sounds (5 of 6 cases), suggesting a ‘dinner-bell’ attraction effect. Responses to mammal-eating killer whale sounds varied with the context of presentation: playback elicited strong avoidance responses by humpback whales in offshore waters during summer (7 of 8 cases), whereas the whales either approached (2 of 4 cases) or avoided (2 of 4 cases) the sound source in inshore waters during winter. These results indicate that humpback whales may be able to functionally discriminate between the sounds of different killer whale ecotypes. Acoustic discrimination of heterospecific sounds may be widespread among marine mammals, suggesting that marine mammals could rely on eavesdropping as a primary source of information to make decisions during heterospecific encounters.
... Bray elements may have a similar social basis, especially considering that bottlenose dolphins are also vocal learners. However, for birds and whales, songs have been linked with sexual interactions 69,70 whereas for dolphins brays have been associated with feeding events 71,72 , and social and aggressive behaviour 73 . One possibility is that brays might encode specific semantic content (prey-related or other) and may be produced only in certain social/cultural/environmental contexts, which would account for the geographic variability found in this study. ...
Article
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Acoustical geographic variation is common in widely distributed species and it is already described for several taxa, at various scales. In cetaceans, intraspecific variation in acoustic repertoires has been linked to ecological factors, geographical barriers, and social processes. For the common bottlenose dolphin ( Tursiops truncatus ), studies on acoustic variability are scarce, focus on a single signal type—whistles and on the influence of environmental variables. Here, we analyze the acoustic emissions of nine bottlenose dolphin populations across the Atlantic Ocean and the Mediterranean Sea, and identify common signal types and acoustic variants to assess repertoires’ (dis)similarity. Overall, these dolphins present a rich acoustic repertoire, with 24 distinct signal sub-types including: whistles, burst-pulsed sounds, brays and bangs. Acoustic divergence was observed only in social signals, suggesting the relevance of cultural transmission in geographic variation. The repertoire dissimilarity values were remarkably low (from 0.08 to 0.4) and do not reflect the geographic distances among populations. Our findings suggest that acoustic ecology may play an important role in the occurrence of intraspecific variability, as proposed by the ‘environmental adaptation hypothesis’. Further work may clarify the boundaries between neighboring populations, and shed light into vocal learning and cultural transmission in bottlenose dolphin societies.
... Singing whales typically travel at below-average migratory speeds while engaged in song and tend to be alone (Noad and Cato 2007). Nevertheless, they frequently attract brief visits from nearby whales (mostly males) who are thought to be "prospecting" for the presence of a female (Smith et al. 2008;Herman 2017). As such, we considered singers to be the individuals most likely to not only initiate but also attract interactions with female and male conspecifics, respectively. ...
Article
During migration, humpback whale (Megaptera novaeangliae) adult females and their calves use acoustic calling to help maintain contact. The signals produced by these pairs, however, may unintentionally attract nearby breeding males, which can result in interactions that have negative physical and physiological effects on the calf. Therefore, maternal females must choose the vocal and/or behavioral strategy that most effectively balances intra-pair communication with male avoidance. Here, we analyzed differences in adult female-calf vocal activity and movement behavior according to the presence of, and distance to, singing whales and other groups likely to contain males. The results of this study found that these pairs make only minimal changes to their vocal behavior in response to nearby males, suggesting that they have instead evolved calls that are naturally difficult to detect (i.e., produced at significantly lower rates and acoustic levels than other whale groups, resulting in a restricted active space). In addition, they maintain spatial separation from nearby groups by moving to shallower, inshore waters, increasing their proportion of time spent near the surface, and favoring a direct migratory course. This combination of cryptic strategies balances avoidance of unwanted conspecific interaction with the necessity of continued contact between maternal female humpback whales and their calves.
... One answer relates to the kind of musical features absent in humpback song, specifically the lack of temporal synchronization between individuals, resulting in an "asynchronous chorus" (Herman, 2017). Savage et al. present convincing evidence that synchronization can give rise to prosocial behaviour, we shouldn't be too surprised to find it absent in communities lacking long-term bonds. ...
Article
We propose that not social bonding, but rather a different mechanism underlies the development of musicality: being unable to survive alone. The evolutionary constraint of being dependent on other humans for survival provides the ultimate driving force for acquiring human faculties such as sociality and musicality, through mechanisms of learning and neural plasticity. This evolutionary mechanism maximizes adaptation to a dynamic environment.
... Let us now investigate song culture and dynamics. Male humpback whales sing a long, complex, stereotyped, and hierarchically structured vocal display termed "song" (Payne and McVay 1971;Herman and Tavolga 1980), which functions in sexual selection to attract a mate and/or mediate male-male interactions (Herman 2017). Most males within a population sing a similar song at any time; that is, they sing songs which share similar themes, phrases, and units, as well as the same arrangement of song components. ...
Chapter
CultureCulture, the sharingSharingof behaviorsBehaviors or information within a community acquired through some form of social learningSocial learning from conspecifics, represents a “second inheritance system”. This assertion, while still controversial, is a clear indication that cultureCulture and the study of social learningSocial learning in animals is no longer a taboo subject. Some of the strongest evidence for cultureCulture in animals has come from the study of cetaceans; while the focus has typically been on the odontocetes (mainly sperm whalesSperm whale, killer whalesKiller whale, and bottlenose dolphinsBottlenose dolphin), baleen whales provide important, unique, and robust evidence for cultural processesCultural processes. Baleen whales undertake a myriad of behaviorsBehaviors across a variety of contexts. Some of these behaviorsBehaviors have been investigated with a culturalCultural lens and have clearly shown maternally directedMaternally directed (and thus culturally transmittedCulturally transmitted) site fidelitySite fidelityto breedingBreeding, feedingFeedingand migratory routesMigratory route, dynamic cultural transmissionCultural transmissionof songSong, and social transmissionSocial transmission of novel feedingFeeding techniques. Undertaking culturalCultural studies in large, free-ranging cetaceans requires multiyear, long-term datasets with enough detail to track changes; such datasets are rare and take decades to accumulate. However, we are now seeing a number of such datasets come to light, and the results are spectacular. Here, we first provide an overview of cultureCulture and its transmissionTransmission; we then highlight some of the clearest examples of baleen whale cultureCulture to date, concluding with research considerations. CultureCulture and its influence on the lives of cetaceans can no longer be ignored as, to paraphrase some of the pioneers in the cetacean cultureCulture field, it is now clear that cultureCulture rules their [cetaceans’] lives.
... This increase (although only an estimate) is similar to a growing body of evidence that suggests that, for some mammalian and avian species, acoustic communication is less expensive than previously thought (e.g. Ilany et al. 2013;Herman 2017;Pedersen et al. 2020). For example, using thermography, Ward and Slater (2005) estimated that singing Waterslager canaries (Serinus canaria) increase their MR by 14.5% compared to sitting individuals. ...
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The use of songs for mate-attraction is common. Intensive songs may indicate high energetic investment, reflecting an individual’s resource-holding potential and attractiveness as a prospective mate. Consequently, there can be a direct relationship between song metrics and lifetime reproductive success. While singing is held to be energetically costly, quantitative studies in mammals are lacking. Here, we present an exploratory analysis of energetic costs in a singing bat (Mystacina tuberculata). We recorded the songs of 12 male bats and quantified skin temperature (Tsk) responses using temperature telemetry to estimate energy expenditure. We hypothesised that singing would be energetically costly and predicted correlations between Tsk and song duty cycle and between duty cycle and body size. Contrary to our expectations, we found estimated energetic expenditure while singing to be comparatively low. We also found no relationship between estimated energy expenditure and duty cycle, and neither estimated energy expenditure nor duty cycle was correlated with body size. Our results suggest that energetic costs of singing in bats may be lower than previously assumed, and that song output may convey only limited fitness information. Significance statement Song is commonly used to communicate information related to mate-attraction or territory defence. Some aspects of song production require more energy to produce, making them an honest signal of a singer’s investment. While our knowledge of bird song and its relationship to mating success is well developed, a similar understanding regarding mammalian song is severely lacking. Numerous bat species produce song, yet we know little about the energetics of song production in this large and diverse order. Using temperature telemetry, we estimate the costs of singing in a free-living lek-breeding bat. To our knowledge, this is the first study to estimate the energetic costs of song production in a mammal.
... One answer relates to the kind of musical features absent in humpback song, specifically the lack of temporal synchronization between individuals, resulting in an "asynchronous chorus" (Herman, 2017). Savage et al. present convincing evidence that synchronization can give rise to prosocial behaviour, we shouldn't be too surprised to find it absent in communities lacking long-term bonds. ...
Article
Savage et al. argue for musicality as having evolved for the overarching purpose of social bonding. By way of contrast, we highlight contemporary predictive processing models of human cognitive functioning in which the production and enjoyment of music follows directly from the principle of prediction error minimization.
... This seasonal shift in behavior is also reflected in their acoustic behavior. During winter on the breeding grounds, male humpback whales frequently produce long complex songs as sexual displays (Payne and McVay, 1971;Winn and Winn, 1978), while on feeding grounds during summer, male humpback whales mostly sing during late spring and late autumn (Clark and Clapham, 2004;Herman, 2017;Stimpert et al., 2012). In addition, humpback whales also produce non-song vocalizations, i.e., calls, which have been recorded during migration and on breeding and feeding grounds (Dunlop et al., 2007;Fournet et al., 2015;Parks et al., 2014;Silber, 1986;Stimpert et al., 2011;Thompson et al., 1986). ...
Article
Male humpback whales (Megaptera novaeangliae) sing in mating aggregations in the form of song displays, but much less is known about how both sexes use sound on their feeding grounds. Here, we test different hypotheses about the function of vocalizations in 14 foraging humpback whales tagged with sound and movement recording Dtags in Greenland. We show that this population of foraging humpback whales have an overall low call rate of 11.9 calls h⁻¹ (inter-quartile range = 12.1) with no support for the hypotheses that they employ sound in the localization or manipulation of prey nor in the coordination of lunge feeding. The calls had a mean received level of 135 ± 5dB re 1 μPa, which is some 30 dB lower than maximum levels of song recorded on similar deployed tags, suggesting a much smaller active space of these vocalizations. This reduced active space might, in concert with low call rates, serve to mitigate eavesdropping by predatory killer whales or conspecifics competing for the same prey resources. We conclude that feeding humpback whales in Greenland produce low level, infrequent calls suggesting that calling is not a prerequisite for successful feeding, but likely serves to mediate within group social interactions.
... Male humpback whales sing, at any timepoint, a single long, stereotyped, complex and hierarchically structured song [22][23][24]. Although the exact details are still debated (see [26]), song in humpback whales is thought to function in sexual selection. The song is arranged in a nested hierarchy: on the most fundamental level is the 'unit', representing an individual sound; a few units sung in a stereotyped sequence constitute a 'phrase'; phrases are repeated one to many times to make a 'theme'; and finally, a sequence of different themes makes up a song [22,27]. ...
Article
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Humpback whale song is an extraordinary example of vocal cultural behaviour. In northern populations, the complex songs show long-lasting traditions that slowly evolve, while in the South Pacific, periodic revolutions occur when songs are adopted from neighbouring populations and rapidly spread. In this species, vocal learning cannot be studied in the laboratory, learning is instead inferred from the songs' complexity and patterns of transmission. Here, we used individual-based cultural evolutionary simulations of the entire Southern and Northern Hemisphere humpback whale populations to formalize this process of inference. We modelled processes of song mutation and patterns of contact among populations and compared our model with patterns of song theme sharing measured in South Pacific populations. Low levels of mutation in combination with rare population interactions were sufficient to closely fit the pattern of diversity in the South Pacific, including the distinctive pattern of west-to-east revolutions. Interestingly, the same learning parameters that gave rise to revolutions in the Southern Hemisphere simulations gave rise to evolutionary patterns of cultural evolution in the Northern Hemisphere populations. Our study demonstrates how cultural evolutionary approaches can be used to make inferences about the learning processes underlying cultural transmission and how they might generate emergent population-level processes. This article is part of the theme issue ‘Vocal learning in animals and humans’.
... Migrating male humpbacks typically begin to sing when they have encountered a female and sing for longer durations when a female is nearby, suggesting a courtship or mate-attraction function of song [48]. Singing humpback males may, therefore, constitute a 'floating lek' that attracts females to the mating area, potentially stimulating female receptivity [49]. However, males are aggressive towards other singing males and will avoid producing song if another competitive male is close by, suggesting an additional function for intra-sexual selection [50]. ...
Article
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The capacity to learn novel vocalizations has evolved convergently in a wide range of species. Courtship songs of male birds or whales are often treated as prototypical examples, implying a sexually selected context for the evolution of this ability. However, functions of learned vocalizations in different species are far more diverse than courtship, spanning a range of socio-positive contexts from individual identification, social cohesion, or advertising pair bonds, as well as agonistic contexts such as territorial defence, deceptive alarm calling or luring prey. Here, we survey the diverse usages and proposed functions of learned novel signals, to build a framework for considering the evolution of vocal learning capacities that extends beyond sexual selection. For each function that can be identified for learned signals, we provide examples of species using unlearned signals to accomplish the same goals. We use such comparisons to generate hypotheses concerning when vocal learning is adaptive, given a particular suite of socio-ecological traits. Finally, we identify areas of uncertainty where improved understanding would allow us to better test these hypotheses. Considering the broad range of potential functions of vocal learning will yield a richer appreciation of its evolution than a narrow focus on a few prototypical species. This article is part of the theme issue ‘Vocal learning in animals and humans’.
... This technique can be used to monitor anthropogenic noise introduced by vessels (Blair et al., 2016), sonar (Harris et al., 2018), seismic surveys (Pirotta et al., 2014), or underwater explosives (Showen et al., 2018). Many marine species including fish, invertebrates, and marine mammals produce sound in accordance with critical life functions-e.g., reproduction (Herman, 2016;Rowell et al., 2017), territory defense , and foraging (Remage-Healey et al., 2006). Anthropogenic noise can impede the ability of these species to communicate, find prey, or orient themselves within the environment (e.g., Parks et al., 2009;Rossi et al., 2016). ...
Article
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Soundscapes represent an intrinsic aspect of a habitat which, particularly in protected areas, should be monitored and managed to mitigate human impacts. Soundscape ecology characterizes acoustic interactions within an environment, integrating biological, anthropogenic, climatological, and geological sound sources. Monitoring soundscapes in marine protected areas is particularly important due to the reliance of many marine species on sound for biological functions, including communication and reproduction. In this study we establish a baseline understanding of underwater soundscapes within two marine National Park Zones (NPZs) along the east coast of Australia: Cod Grounds Marine Park and an NPZ surrounding Pimpernel Rock within Solitary Islands Marine Park. In each of the NPZs, underwater recorders were deployed twice during the austral winter (33–35 days, 2018 and 60–69 days, 2019) and once during the austral summer (35–71 days, 2018–2019). We used the resulting acoustic recordings to determine hourly presence of anthropogenic and biological sounds between 20 Hz and 24 kHz and analyze their contributions to patterns of received sound levels. Sounds from vessels were recorded on most days throughout monitoring but were not found to influence long-term patterns of sound levels over their corresponding frequencies. Biological sources included dolphins, snapping shrimp, fish choruses, humpback whales, and dwarf minke whales. Dolphins, snapping shrimp, and fish choruses were present in all deployments. Median ambient sound levels showed a consistent diel pattern with increased levels resulting from crepuscular fish choruses combined with a higher intensity of snapping shrimp snaps during those times. Singing humpback whales strongly influenced the overall sound levels throughout the winter migration, while dwarf minke whales were consistently detected in the 2019 winter deployment but were only present in 2 h among the earlier deployments. Patterns of acoustic spectra were similar between the two NPZs, and patterns of soundscape measurements were observed to be driven by seasonal differences in biological contributions rather than anthropogenic sound sources, indicating that these NPZs are not yet heavily impacted by anthropogenic noise. These baseline measurements will prove invaluable in long-term monitoring of the biological health of NPZs.
Article
Collective migration occurs throughout the animal kingdom, and demands both the interpretation of navigational cues and the perception of other individuals within the group. Navigational cues orient individuals towards a destination, while it has been demonstrated that communication between individuals enhances navigation through a reduction in orientation error. We develop a mathematical model of collective navigation that synthesizes navigational cues and perception of other individuals. Crucially, this approach incorporates uncertainty inherent to cue interpretation and perception in the decision making process, which can arise due to noisy environments. We demonstrate that collective navigation is more efficient than individual navigation, provided a threshold number of other individuals are perceptible. This benefit is even more pronounced in low navigation information environments. In navigation ‘blindspots’, where no information is available, navigation is enhanced through a relay that connects individuals in information-poor regions to individuals in information-rich regions. As an expository case study, we apply our framework to minke whale migration in the northeast Atlantic Ocean, and quantify the decrease in navigation ability due to anthropogenic noise pollution.
Article
Focus on the evolutionary origins of musicality has been neglected relative to attention on language, so these new proposals are welcome stimulants. We argue for a broad comparative approach to understanding how the elements of musicality evolved, and against the use of overly simplistic evolutionary accounts.
Article
Documented cases of cetacean births in the wild are rare. While there are currently no direct observations of a complete humpback whale birth, they are one of the few large whale species where observers have been present during a birthing event. We compiled eye-witnessed accounts of all known humpback whale birthing events and found nine well-documented cases globally (three published and six “new” unpublished). In two-thirds of the accounts another “escort” whale was present and in close association with the birthing female, and of these, most cases involved multiple escorts (n = 4). We describe details of birthing events, including mother, neonate and escort(s)’ behavior, neonate appearance, and discuss reasons for escort presence during parturition. We note that immediately postpartum: (1) blood and/or placenta were not always apparent during above water observations, (2) females often (but not always) supported calves at the surface, (3) constant travel and tail slapping were typical neonate behaviors, (4) two cases of temporary calf abandonment (<10 min), and (5) evidence of shark scavenging (of placenta) and possible predation attempts (of neonate). Lastly, we suggest curled tail flukes as an additional trait for identifying neonates and note that fetal folds are not always evident in newborn humpback whales.
Chapter
It has been fifty years since Payne and McVay’s seminal publication on the strange and beautiful sounds of the humpback whaleHumpback whale (Megaptera novaeangliaeMegaptera novaeangliae), the study which inspired decades of research into their complex, underwater acoustic world. In the subsequent five decades, there probably have been more research projects and publications on humpback whaleHumpback whale song than on the vocal behavior of any other baleen whale. What makes humpback song so unique? What have we learned? What questions remain? With this chapter, we explore these questions with an eye toward the overarching theme of studies that address proximate mechanisms (the “how do humpback whalesHumpback whaledo this?” questions) versus those that inquire about ultimateProximate vs ultimate causes (the “why do humpback whalesHumpback whaledo this?” questions). We draw a distinction between studies that focus on singing behavior, versus those that use song as a proxy to investigate other biological processes. We take the reader through a historical review of the literature, ending with a series of observations about the unanswered questions intended to provoke new ideas and new lines of inquiry. Through this exploration, we hope to synthesize a global body of research to identify common themes and probe the lingering gaps in our understandings of humpback whaleHumpback whale song.
Thesis
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Humpback whales (𝘔. 𝘯𝘰𝘷𝘢𝘦𝘢𝘯𝘨𝘭𝘪𝘢𝘦) are among the most vocally complex animals. Besides the stereotyped song produced by males mainly during the reproductive season, humpback whales have a diverse repertoire of non-song vocalizations, known as social calls (SCs). These are usually considered random displays, produced in all contexts, regardless of the whales' sex or age, but little is known about calling behavior or call function. Most research on SCs have focus on the Northeast and Southwest Pacific and Northwest Atlantic populations. The SC repertoire and the calling behavior of the humpback whales of the Southeast Pacific (Breeding Stock G) has only been partially documented in two studies. Here two different passive acoustic methodologies (over-the-sides hydrophones and DTAGs) were used to investigate diversity, associated behavior, and context of the Breeding Stock G humpback whales’ SCs in their breeding and feeding grounds. The Stock G catalogue is composed of 48 call types, from which a high percentage are blend and unknown calls. Call rates in the breeding ground of Colombia were higher than in the feeding ground of the Western Antarctic Peninsula. Some call types were frequently found in a competitive context, denoting a possible motivational feature (aggression) of such calls. In Antarctica, a third of the vocal activity was related to surfacing events, and calling behavior was influenced by the presence of conspecifics, the tag (individual), and the period of the day. The results showed that most calls were produced and combined in non-random patterns within bouts. Some of the bouts composed of pulses showed stable structures across time and space similar to bouts reported in allopatric populations. Finally, a new vocal display of repetitive series of cry-like calls, named Repetitive Tones (RTs), is reported in Colombia. Different scenarios about the origin and the function of these calls are discussed. The resemblance of RTs to feeding calls from Alaskan whales may support cross-equatorial displacement between North and Southeastern Pacific populations. The future use of DTAGs in the breeding ground to record SCs and the expanded database of different individuals from Antarctica will allow for deeper analyses of Stock G diversity and calling behavior, better facilitating comparisons between feeding and breeding areas. Community-wide agreements on definition and nomenclature of SCs are necessary for the refinement of the Social Call Global Catalogue and cross-population comparisons.
Article
No PDF available ABSTRACT Passive acoustic monitoring (PAM) with autonomous bottom-moored recorders is widely used to study cetacean occurrence, distribution, and behaviors, as it is less constrained by factors that often limit other traditional visual observation methods, such as weather and accessibility. During the breeding season, male humpback whales produce an elaborate acoustic display known as “song.” The typical asynchronous chorusing of numerous singing males at any one time can provide challenges for monitoring abundance using PAM. Chorusing becomes the dominant source of low frequency (0–1.5 kHz) noise in the marine soundscape in Hawai‘i and seasonal levels mirror the whales’ migratory patterns. However, the relationship between chorusing levels and overall whale numbers, including non-singing whales (e.g., mother-calf pairs and juveniles), has remained poorly defined. We combined long-term PAM conducted between 2014/15 and 2020/21 off West Maui with concurrent visual land- and vessel-based observations. We found that daily median root-mean-squared sound pressure levels (RMS SPLs) correlate strongly with whale numbers (land: 0.71 ≤ R² ≤ 0.76, vessel: 0.81 ≤ R² ≤ 0.85 for three different PAM locations). Applying these results, we were able to use PAM to document significant population fluctuations between 2015 and 2021, as well as study habitat use patterns off West Maui.
Thesis
In humpback whales (Megaptera novaeangliae), maintaining social bonds between females and their newborns involves different sensory modalities such as hearing, touching and vision. While acoustic communication in male singers of this species has been extensively studied, social sounds, especially those produced by the females and their newborns have been poorly documented. This study describes the social sounds present in acoustic recordings focused on mother-calf groups and discusses the vocalizations used by females and calves in mother-offspring interactions. By considering the most frequent sounds from their vocal repertoire, an analysis focused on the determination of the source of the low-frequency sounds produced by the mother have been carried out and analyses were performed to investigate the individuality of some vocalizations belonging to the mothers and the calves. A description of the behavioural context of their vocal production was performed and the diving profiles of mother-calf pairs were described. Moreover, females with their calves spend a lot of time on the water surface. Mothers are often static at the surface while calves move around them. This study is also dedicated to the understanding of their surface behaviours, considering the behaviours initiated by calves. A series of analyses were carried out to determine whether calves exhibited lateralization behaviours in relation to their mothers. Finally, by using photogrammetry method, mother-calf lengths were measured, and calves spatial range around their mothers was investigated.
Article
Full-text available
Passive acoustic monitoring (PAM) with autonomous bottom-moored recorders is widely used to study cetacean occurrence, distribution and behaviors, as it is less affected by factors that limit other observation methods (e.g., vessel, land and aerial-based surveys) such as inclement weather, sighting conditions, or remoteness of study sites. During the winter months in Hawai‘i, humpback whale male song chorusing becomes the predominant contributor to the local soundscape and previous studies showed a strong seasonal pattern, suggesting a correlation with relative whale abundance. However, the relationship between chorusing levels and abundance, including non-singing whales, is still poorly understood. To investigate how accurately acoustic monitoring of singing humpback whales tracks their abundance, and therefore is a viable tool for studying whale ecology and population trends, we collected long-term PAM data from three bottom-moored Ecological Acoustic Recorders off west Maui, Hawaii during the winter and spring months of 2016–2021. We calculated daily medians of root-mean-square sound pressure levels (RMS SPL) of the low frequency acoustic energy (0–1.5 kHz) as a measure of cumulative chorusing intensity. In addition, between December and April we conducted a total of 26 vessel-based line-transect surveys during the 2018/19 through 2020/21 seasons and weekly visual surveys ( n = 74) from a land-based station between 2016 and 2020, in which the location of sighted whale pods was determined with a theodolite. Combining the visual and acoustic data, we found a strong positive second-order polynomial correlation between SPLs and abundance (land: 0.72 ≤ R ² ≤ 0.75, vessel: 0.81 ≤ R ² ≤ 0.85 for three different PAM locations; Generalized Linear Model: p land ≪ 0.001, p vessel ≪ 0.001) that was independent from recording location ( p land = 0.23, p vessel = 0.9880). Our findings demonstrate that PAM is a relatively low-cost, robust complement and alternative for studying and monitoring humpback whales in their breeding grounds that is able to capture small-scale fluctuations during the season and can inform managers about population trends in a timely manner. It also has the potential to be adapted for use in other regions that have previously presented challenges due to their remoteness or other limitations for conducting traditional surveys.
Article
Studies of humpback whale (Megaptera novaeangliae) habitat use in their Hawaiian breeding grounds have revealed that mother‐calf pairs favor shallow waters to avoid harassment from males. However, human activity in these same waters may exert an opposing force on habitat use. To investigate this hypothesis, instantaneous scan samples of whale and vessel distribution were collected from West Maui, Hawaiʻi. Theodolite position fixes were combined with GIS techniques to determine the depths and seabed terrain type occupied by 161 humpback whale pods containing a calf (calf pods) and 872 pods without a calf (noncalf pods). We found no significant diurnal trends for noncalf pods, but calf pods occupied progressively deeper water over the course of each day. There was no evidence that this shift was related to (1) a “spillover” resulting from high mother‐calf density in shallow water, (2) harassment by males occupying the same space as mother‐calf pairs, or (3) the presence of mainly older and larger calves. However, while diurnal trends of whale‐watching vessels largely mirrored those of mother‐calf pods, nonwhale‐watching vessels tended to remain in shallower waters throughout the day. These results suggest that nearshore vessels may negatively impact the natural preference of mother‐calf pairs for shallow waters.
Chapter
Mysticetes (baleen whalesBaleen whales) have an amazing array of adaptations of mammalian traits and functions enhanced for aquatic submersion. In this chapter, special emphasis is placed on anatomy and physiology of adaptions that enable communicationCommunication(soundSound production and reception) in water, including during divingDiving. Whenever possible, data revealing anatomical differences will be pointed out at the family level for balaenidsBalaenids(bowhead whaleBowhead whaleBalaena mysticetus, and right whalesRight whaleEubalaena glacialis, E. japonica, E. australis), neobalaenidNeobalaenid(pygmy right whalePygmy right whale, Caperea marginata), eschrichtiidEschrichtiid(gray whaleGray whaleEschrichtius robustus), and balaenopteridsBalaenopterids(rorqual whalesRorqual whales, i.e., whales with throat pleatsThroat pleats, including humpback Megaptera novaeangliae, and the many species of the genus Balaenoptera, including minke whaleMinke whaleB. acutorostrata, Antarctic minke whaleAntarctic minke whaleB. bonaerensis, blue whaleBlue whaleB. musculus, fin whaleFin whaleB. physalus, sei whaleSei whaleB. borealis, Bryde’s whaleBryde’s whaleB. edeni, and Omura’s whaleOmura’s whaleB. omurai). Some species groupings (e.g., the various right whalesRight whale) or subspecies groupings (e.g., subspecies of blue whalesBlue whale) will not be addressed if there is no literature to indicate a difference, and the assumption is made that their anatomy is similar enough to be generalized for the whole group. In many cases, an anatomical feature may be discussed in generalities because it is present in all mysticetes.
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Humpback whalesHumpback whale(Megaptera novaeangliae)Megaptera novaeangliae occur in all major oceans. Given this worldwide distribution, and since they tend to migrate along coastlines, they are one of the best known of the baleen whalesBaleen whale. Humpbacks are relatively easy to find and easy to observe. This, along with their surface behaviorsBehavior and attraction to vessels, makes them popular with whale-watching businesses. In the scientific world, their songSong and behaviorsBehavior have been studied since the 1970s, producing hundreds of scientific papers. Despite this, there are still many unsolved mysteries. Why do humpbacks sing (Chaps. 8 and 11), how do they locate their prey (Chap. 5), and how do they navigate when migrating (Chap. 4)? In this chapter, we focus on the mysteries of their social communicationCommunication. Communication and social complexitiesSocial complexity often go hand in hand. Animals with more complex social structuresSocial structure tend to have more complex vocal repertoiresVocal repertoire, perhaps peaking, with humans. Within the baleen whalesBaleen whale, humpback whalesHumpback whale are considered an exception. Present knowledge indicates that humpbacks have a relatively complex acoustic repertoireAcoustic repertoire but work on their breedingBreedingsocial systemSocial system has considered them to be socially simple. Animals regarded as having a simple social structureSocial structure tend to have small group sizes and a lack of repeat associations between individuals over time. Humpback whalesHumpback whale meet this criteria in that they form temporary associations between a small number of individuals, and these associations are not repeated over time, leading to the conclusion that their social structureSocial structureis simple and individually basedIndividually-based. Why then do humpbacks have what could be considered a complex acoustic repertoireAcoustic repertoire? Is the conclusion that they possess a simple social structureSocial structure supported by best available scientific evidence? This chapter illustrates that humpbacks may in fact have a complex social structureSocial structure, with complexity defined differently than traditional definitions of complexity (number in a group, number of repeat associations). Rather than forming large permanent groups with repeated interactions between individuals, humpback whalesHumpback whale during the breedingBreeding season form networks that encompass multiple groups. These groups are frequently changing membership, and animals are constantly moving into, and out of this network. Whales must therefore continuously assess, and respond to, a changing social environment. Given that humpbacks likely rely on acoustic communicationCommunication to manage these interactions, this added layer of social complexitySocial complexity may go toward explaining their large and varied vocal repertoireVocal repertoire. Perhaps communicative and social complexitiesSocial complexity do go hand in hand for the humpback whaleHumpback whale.
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Fifty animals were identified in 1986, 40 in 1987 and 35 in 1988 for a total of 108. Eleven individuals were common to 1986/1987 and size to 1987/1988. Three individuals were common for the three years. Estimates of the population for the 3 yr ranged from 170-450. The importance of Gorgona as a calving area is shown by the fact that 26.5% of animals were calves. -from Author
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Between 1991 and 1997 the southeastern Pacific humpback whale (Megaptera novaeangliae) stock was studied off the central part of Ecuador (01°24'S, 80°55'W) during the breeding season (June-September). For this purpose, surveys were carried out onboard whale-watching boats at two different sites: Puerto López and Puerto Cayo. Some population parameters such as distribution, group structure, population size, calving rate and behavior were evaluated. The first whales arrived by the end of May, they peaked in July and most of them had left the area by the end of September. Along the Puerto López route, groups were significantly larger (P
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We assessed the social structure and behavior of humpback whale (Megaptera novaeangliae) competitive groups off Ecuador between July and August 2010. During this time we followed 185 whales in 22 competitive groups for 41.45 hr. The average group size was 8.4 animals (SD = 2.85). The average sighting time was 113.05 min/group (SD = 47.1). We used photographs of dorsal fins and video to record interactions and estimate an association index (AI) between each pair of whales within the groups. Sightings were divided into periods, which were defined by changes in group membership. On average, group composition changed every 30.2 min, which confirms that the structure of competitive groups is highly dynamic. Interactions between escorts characterized by low level of aggression. At least 60% of escorts joined or left together the group in small subunits between two and five animals, suggesting some type of cooperative association. Although singletons, as well as pairs or trios were able to join competitive groups at any moment, escorts that joined together were able to stay longer with the group and displace dominant escorts. Genetic analysis showed that in three occasions more than one female was present within a competitive group, suggesting either males are herding females or large competitive groups are formed by subunits. Males and females performed similar surface displays. We propose that competition and cooperation are interrelated in humpback whales' competitive groups and that male cooperation would be an adaptive strategy either to displace dominant escorts or to fend off challengers.
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A new, fully dated total-evidence phylogeny of baleen whales (Mysticeti) shows that evolutionary phases correlate strongly with Caenozoic modernization of the oceans and climates, implying a major role for bottom-up physical drivers. The phylogeny of 90 modern and dated fossil species suggests three major phases in baleen whale history: an early adaptive radiation (36–30 Ma), a shift towards bulk filter-feeding (30–23 Ma) and a climate-driven diversity loss around 3 Ma. Evolutionary rates and disparity were high following the origin of mysticetes around 38 Ma, coincident with global cooling, abrupt Southern Ocean eutrophication and the development of the Antarctic Circumpolar Current (ACC). Subsequently, evolutionary rates and disparity fell, becoming nearly constant after approximately 23Ma as the ACC reached its full strength. By contrast, species diversity rose until 15Ma and then remained stable, before dropping sharply with the onset of Northern Hemisphere glaciation. This decline coincided with the final establishment of modern mysticete gigantism and may be linked to glacially driven variability in the distribution of shallow habitats or an increased need for long-distance migration related to iron-mediated changes in glacial marine productivity.
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Understanding the patterns of spatial and temporal distribution in threshold habitats of highly migratory and endangered species is important for understanding their habitat requirements and recovery trends. Herein, we present new data about the distribution of humpback whales (Megaptera novaeangliae) in neritic waters off the northern coast of Peru: an area that constitutes a transitional path from cold, upwelling waters to warm equatorial waters where the breeding habitat is located. Data was collected during four consecutive austral winter/spring seasons from 2010 to 2013, using whale-watching boats as platforms for research. A total of 1048 whales distributed between 487 groups were sighted. The spatial distribution of humpbacks resembled the characteristic segregation of whale groups according to their size/age class and social context in breeding habitats; mother and calf pairs were present in very shallow waters close to the coast, while dyads, trios or more whales were widely distributed from shallow to moderate depths over the continental shelf break. Sea surface temperatures (range: 18.2–25.9°C) in coastal waters were slightly colder than those closer to the oceanic realm, likely due to the influence of cold upwelled waters from the Humboldt Current system. Our results provide new evidence of the southward extension of the breeding region of humpback whales in the Southeast Pacific. Integrating this information with the knowledge from the rest of the breeding region and foraging grounds would enhance our current understanding of population dynamics and recovery trends of this species.
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Most known concentrations of humpback whales in the southern hemisphere were exploited by commercial whaling operations, first on tropical breeding grounds during the 19th cen-tury and then in Antarctic feeding areas and along migratory corridors during the 20th century. How-ever, whaling logbooks of 19th century whalers show almost no records of catches in some regions of current concentration, notably eastern Polynesia, suggesting that humpback whales were formerly absent from these regions or that the locations of their primary concentrations were unknown to early whalers. Here we investigate the population structure of humpback whales across the South Pacific and eastern Indian oceans, with an interest in the origins of whales in eastern Polynesia, using an extensive collection of mitochondrial DNA (mtDNA) sequences obtained from living whales on 6 breeding grounds: New Caledonia, Tonga, Cook Islands, eastern Polynesia (Society Islands of French Polynesia), Colombia and Western Australia. From a total of 1112 samples we sequenced 470 bp of the mtDNA control region, revealing 115 unique haplotypes identified by 71 variable sites. We found significant differentiation, at both the haplotype and nucleotide level (F ST = 0.033; Φ ST = 0.022), among the 6 breeding grounds and for most pair-wise comparisons. The differentiation of the eastern Polynesia humpback whales is consistent with the hypothesis of a relic subpopulation, rather than vagrancy or colonization from known neighboring breeding grounds. Regardless of their origin, it seems probable that islands of eastern Polynesia are now the primary breeding grounds for hump-back whales feeding in management Area VI (170 to 120° W) of the Antarctic, as defined by the Inter-national Whaling Commission.
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Humpback whale Megaptera novaeangliae songs have been proposed as a means to define stocks or coherent population units, based on the assumption that if individuals sing the same complex, ever-changing song, then they must associate. Songs from the Philippines (Babuyan Islands), Japan (Ogasawara) and Hawaii in 2006 were compared to examine the relationship of these populations as determined by song composition. A total of 13 phrases (including phrase variants) were identified from the sample overall. Philippine and Japan songs were composed of the same 9 phrases, while Hawaii song had these 9 phrases, plus 4 unique phrases. Common phrases were presented by singers in the same pattern in all 3 regions. Comparison of phrase use and proportion found a high correlation between the Philippines and Japan (r = 0.876, p < 0.001), and moderate correlations between Japan and Hawaii (r = 0.583, p = 0.029) and the Philippines and Hawaii (r = 0.570, p = 0.033). With the Japan and Philippines sites 2300 km apart and 6200 and 8400 km from Hawaii, respectively, this suggests a relationship between degree of separation and degree of song difference. The range of differences between songs is consistent with a 2-stage splitting of the migratory stream into separate winter assemblies where song divergence may occur. Partial similarity of song (versus entirely same or different) suggests some components are more sensitive to change than others. The variable pace of change may complicate use of song as an index of recent association, especially between populations with different social circumstances that presumably govern song change.
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Humpback whales (Megaptera novaeangliae) annually undertake the longest migrations between seasonal feeding and breeding grounds of any mammal. Despite this dispersal potential, discontinuous seasonal distributions and migratory patterns suggest that humpbacks form discrete regional populations within each ocean. To better understand the worldwide population history of humpbacks, and the interplay of this species with the oceanic environment through geological time, we assembled mitochondrial DNA control region sequences representing approximately 2700 individuals (465 bp, 219 haplotypes) and eight nuclear intronic sequences representing approximately 70 individuals (3700 bp, 140 alleles) from the North Pacific, North Atlantic and Southern Hemisphere. Bayesian divergence time reconstructions date the origin of humpback mtDNA lineages to the Pleistocene (880 ka, 95% posterior intervals 550-1320 ka) and estimate radiation of current Northern Hemisphere lineages between 50 and 200 ka, indicating colonization of the northern oceans prior to the Last Glacial Maximum. Coalescent analyses reveal restricted gene flow between ocean basins, with long-term migration rates (individual migrants per generation) of less than 3.3 for mtDNA and less than 2 for nuclear genomic DNA. Genetic evidence suggests that humpbacks in the North Pacific, North Atlantic and Southern Hemisphere are on independent evolutionary trajectories, supporting taxonomic revision of M. novaeangliae to three subspecies.
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Large-scale research vessel surveys were conducted annually from 1986 through 1990 by the US National Marine Fisheries Service to monitor the abundance of dolphin populations in the E tropical Pacific (ETP). Distribution maps are presented for all 29 species. Data from all five surveys were pooled to give single estimates of abundance in the EPT for 24 stocks of cetaceans. Abundance estimates totaled 9.6 million animals for all dolphin species (subfamilies Delphininae and Steninae), 292 800 for all species in the subfamily Globicephalinae, 45 300 for all species in the family Ziphiidae (beaked whales), 33 881 for all species in the superfamily Physeteroidea, and 14 431 for two species in the family Balaenopteridae (rorquals). -from Authors
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About 70 million years ago, the terrestrial ancestors of whales and dolphins reentered the ocean where life originally began. Not only did this require dramatic shifts in locomotion for swimming and in respiration for diving, but the ocean also presented a very different sensory environment. The explosive way in which cetaceans breathe reduced the usefulness of olfaction, which has limited utility underwater. Light propagates great distances rapidly in air, which makes vision particularly useful for sensing distant objects on land or in air, but light does not propagate well in water. Few objects can be seen underwater at ranges of more than a few tens of meters. By contrast, sound travels particularly well underwater. The potential for the acoustic modality to sense distant sources of sound is highlighted by recent discoveries that we can detect low-frequency calls of whales at ranges of hundreds and sometimes thousands of kilometers (Costa 1993; Clark 1994b, 1995).
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