Adult female-calf acoustic communication signals in migrating east Australian humpback whales

Indeck, Katherine L.; Girola, E.; Torterotot, Maelle; Noad, Michael J.; Dunlop, Rebecca A.

doi:10.1080/09524622.2020.1742204

Cited by 16 publications

(20 citation statements)

References 50 publications

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Section: Discussionsupporting

confidence: 91%

“…Our findings reinforce the notion brought forward by many previous studies that the humpback whale repertoire contains some discrete calls, as well as many graded calls (Chabot, 1988; Dunlop, 2017; Dunlop et al, 2007; Fournet et al, 2015; Indeck et al, 2020; Rekdahl et al, 2013; Stimpert et al, 2011). This phenomenon has been described in a variety of other species including koalas ( Phascolarctos cinereus ; Charlton, 2015), Risso's dolphins ( Grampus griseus ; Corkeron & Van Parijs, 2001), killer whales ( Orcinus orca ; Ford, 1989), wild boars ( Sus scrofa ; Garcia et al, 2016), Old World monkeys (superfamily Cercopithecoidea; Gautier & Gautier, 1977), and great apes (family Hominidae; Marler & Tenaza, 1977).…”

Section: Discussionsupporting

confidence: 91%

“…The growls and whups present an example of this (Figures 2 and 5; Fournet et al, 2015;Fournet et al, 2018c), whereby the upsweep was likely not captured by manually extracted or computer-generated measurements. Not capturing the variation, compounded with small sample sizes (Fournet et al, 2015(Fournet et al, , 2018bIndeck et al, 2020), likely also contributed to the lower classification success of the rumbles and the growl-moans (Table 5). In all of these cases, experienced observers were able to reliably identify the call types, indicated by high interobserver agreement (Table 5).…”

Section: Discussionmentioning

confidence: 99%

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Humpback whale call repertoire on a northeastern Newfoundland foraging ground

Epp

Fournet

Davoren

2021

Marine Mammal Science

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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.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Humpback whale call repertoire on a northeastern Newfoundland foraging ground

Epp

Fournet

Davoren

2021

Marine Mammal Science

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“…This precluded any analysis of acoustic features (e.g., frequency and bandwidth). The overlapping song also prevented any automated classification techniques like those used in previous social call analyses (Stimpert et al, 2011;Fournet et al, 2015;Rekdahl et al, 2017;Cusano et al, 2020Cusano et al, , 2021Indeck et al, 2021). Therefore, in order to determine call types, the results from a previous humpback social call analysis were used (Cusano et al, 2021) that applied fuzzy k-means (FKM) clustering to humpback calls from the same population (Ferraro and Giordani, 2015;Wadewitz et al, 2015;Fischer et al, 2017).…”

Section: (High) <5mentioning

confidence: 99%

“…Males produce stereotyped songs during the breeding season (Payne and McVay, 1971), and all humpback whales produce a large repertoire of social calls. These calls are produced by all age and sex classes (Winn et al, 1979;Zoidis et al, 2008;Indeck et al, 2021), and in all habitats [e.g., breeding grounds (Tyack and Whitehead, 1983;Silber, 1986), feeding grounds (Jurasz and Jurasz, 1979;D'Vincent et al, 1985;Thompson et al, 1986;Stimpert et al, 2007Stimpert et al, , 2011Parks et al, 2014;Fournet et al, 2015), and on migration (Dunlop et al, 2007(Dunlop et al, , 2008Cusano et al, 2020)]. The number of calls within the repertoire is variable, depending on the population, habitat area, and behavioral context (Dunlop et al, 2007;Stimpert et al, 2008;Fournet et al, 2015;Rekdahl et al, 2017;Cusano et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Socially Complex Breeding Interactions in Humpback Whales Are Mediated Using a Complex Acoustic Repertoire

Cusano

Paton²,

Noad

et al. 2021

Front. Mar. Sci.

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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.

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Humpback whale adult females and calves balance acoustic contact with vocal crypsis during periods of increased separation

Indeck

Noad

Dunlop

2022

Ecology and Evolution

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Acoustic communication is important for animals with dependent young, particularly when they are spatially separated. Maternal humpback whales (Megaptera novaeangliae) use acoustic calling to help minimize the risk of separation from their young calves during migration. These pairs also use acoustic crypsis to minimize detection by males. How they balance a restricted active space with the need to maintain acoustic contact during periods of separation is not yet understood. Here, we analyzed movement metrics of tagged adult female-calf pairs during migration to identify two behavioral states, "resting/milling" and "travelling." When travelling, these pairs dived synchronously and exhibited little to no spatial separation. Alternatively, adult females had significantly longer dive durations (p < .01) when resting, and while they spent prolonged times at depth, calves would surface several times independently. This demonstrated that these pairs are frequently separated during periods of rest. We then determined whether the call rates and acoustic levels of these pairs increased with more frequent separation, finding that both adult females and calves significantly increased their call rates, but not levels, when resting. We also found that adult female-calf pairs have a restricted active space, with less than 15% of calls estimated to be detectable beyond 2 km. However, as with call level, detection distance did not differ significantly between the two behavioral states. In summary, adult female-calf pairs maintain successful communication during periods of separation by calling more frequently rather than by producing louder calls. This strategy aids in maintaining acoustic contact while simultaneously limiting detectability by conspecifics.

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Adult female-calf acoustic communication signals in migrating east Australian humpback whales

Cited by 16 publications

References 50 publications

Humpback whale call repertoire on a northeastern Newfoundland foraging ground

Humpback whale call repertoire on a northeastern Newfoundland foraging ground

Socially Complex Breeding Interactions in Humpback Whales Are Mediated Using a Complex Acoustic Repertoire

Humpback whale adult females and calves balance acoustic contact with vocal crypsis during periods of increased separation

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