Source levels of social sounds in migrating humpback whales (Megaptera novaeangliae) (original) (raw)
Related papers
Non-song acoustic communication in migrating humpback whales ( Megaptera novaeangliae )
Marine Mammal Science, 2008
Humpback whales are renowned for the complex structured songs produced by males. A second, relatively understudied area of humpback acoustic communication concerns un-patterned sounds known as "social sounds," produced by both males and females. These include vocalizations as well as sounds produced at the surface of the water as a result of surface behaviors (e.g., breaching, pectoral slapping). This study describes a portion of the non-song social sound repertoire of southward migrating humpbacks in Australian waters, and explores the social relevance of these sounds. On migration, humpback whales travel in social groups of varying compositions. These social groups are not stable in that humpback whales continually change group composition by splitting from, or joining with, other groups. The results of this study suggest that "breaching" and "slapping" have a communicative function. Other sounds such as "underwater blows" and "cries" were heard mainly in competitive groups while other low-frequency sounds such as "grumbles," "snorts," "thwops," and "wops" may function in intra-or inter-group communication. Particular sounds ("grunts," "groans," and "barks") were almost exclusive to joining pods suggesting a role in social integration. Social sounds in humpbacks may have specific social and behavioral functions relating to social group composition, and the mediation of interactions between these social groups.
Modification of humpback whale social sound repertoire and vocal source levels with increased noise
The Journal of the Acoustical Society of America, 2013
High background noise is an important obstacle in successful receiver signal detection and perception of an acoustic signal. To overcome this problem, animals modify acoustic signals by increasing the repetition rate, duration, amplitude, or frequency range of the signal. Humpback whales are the most vocal of the baleen species in that they use a wide and varied catalogue of social sounds. More than 36 different sound types (vocal sounds and sounds from energetic surface behaviours) were found during a three year study on migrating humpback whales. During periods of high wind noise, humpback whales modify both their acoustic repertoire as well as vocal signal properties. We found that humpback whale groups gradually switched from primarily vocal to primarily surface-generated communication in increasing wind speeds and background noise levels, but kept both signal types in their repertoire. We also found evidence of the Lombard effect, in that in increased winddominated background noise levels, humpback whale groups tended to increase the amplitude of their vocalisations. Determining how whales modify their vocal behaviour in increasing levels of background noise will give us an important insight into how they might cope with increasing levels of anthropogenic noise.
The communication space of humpback whale social sounds in vessel noise
Proceedings of Meetings on Acoustics, 2018
This receiver's detection threshold can be used to define the "communication space" of a signal. If unwanted noise increases, then the size of this space may decrease due to increased signal masking. This, in turn, may have detrimental effects on its ability to obtain important social information. Migrating humpback whales rely on a communication network for social interactions. To generate masking models, and infer communication space in increasing vessel noise, changes in signal-above-noise (SNR) and frequency content of received humpback whale social sounds were modelled with the combined effect of increasing background noise and distance from the source (signaling whales). The signaler distance at which a received signal-to-noise ratio was 0 dB was assumed to be the limit of the communication space. In levels exceeding 110 dB re 1 µPa (vessel within approximately 2.5 km), the received SNR for most vocalizations from a signaler greater than 1 km away was below 0. However, higher frequency vocalizations were generally emitted at lower source levels and therefore had a smaller measured communication space. Comparisons with communication space in wind-dominated noise suggests vessel noise reduced the communication space of vocalizations above that due to typical winddominated noise.
Behavioral Ecology and Sociobiology, 2016
Many theories and communication models developed from terrestrial studies focus on a simple dyadic exchange between a sender and receiver. During social interactions, the "frequency code" hypothesis suggests that frequency characteristics of vocal signals can simultaneously encode for static signaler attributes (size or sex) and dynamic information, such as motivation or emotional state. However, the additional presence of a bystander may result in a change of signaling behavior if the costs and benefits associated with the presence of this bystander are different from that of a simple dyad. In this study, two common humpback whale social calls (Bwopsâ nd Bgrumbles^) were tested for differences related to group social behavior and the presence of bystanders. BWop^parameters were stable with group social behavior, but were emitted at lower (14 dB) levels in the presence of a nearby singing whale compared to when a singing whale was not in the area. BGrumbles^were emitted at lower (30-39 Hz) fundamental frequencies in affiliative compared to non-affiliative groups and, in the presence of a nearby singing whale, were also emitted at lower (14 dB) levels. Vocal rates did not significantly change. The results suggest that, in humpbacks, the frequency in certain sound types relates to the social behavior of the vocalizing group, implying a frequency code system. The presence of a nearby audible bystander (a singing whale) had no effect on this frequency code, but by reducing their acoustic level, the signal-to-noise ratio at the singer would have been below 0, making it difficult for the singer to audibly detect the group. Significance statement The frequency, duration, and amplitude parameters of humpback whale social vocalizations were tested between different social contexts: group social behavior (affiliating versus nonaffiliating), the presence of a nearby singing whale, and the presence of a nearby non-singing group. BGrumbles^(commonly heard low-frequency unmodulated sounds) frequencies were lower in affiliating groups compared to non-affiliating groups, suggesting a change in group motivation (such as levels of aggression). BWop^(another common sound type) structure (frequency and duration) was similar in affiliating and non-affiliating groups. In the presence of an audible bystander (a singing whale), both sound types were emitted at similar rates, but much lower amplitudes (14 dB), vastly reducing the detectability of these sounds by the singer. This suggests that these groups were acoustically avoiding the singing whale. They did not, however, acoustically respond to the presence of a nearby non-singing group.
Evidence for acoustic communication among bottom foraging humpback whales
Scientific Reports, 2014
Humpback whales (Megaptera novaeangliae), a mysticete with a cosmopolitan distribution, demonstrate marked behavioural plasticity. Recent studies show evidence of social learning in the transmission of specific population level traits ranging from complex singing to stereotyped prey capturing behaviour. Humpback whales have been observed to employ group foraging techniques, however details on how individuals coordinate behaviour in these groups is challenging to obtain. This study investigates the role of a novel broadband patterned pulsed sound produced by humpback whales engaged in bottom-feeding behaviours, referred to here as a 'paired burst' sound. Data collected from 56 archival acoustic tag deployments were investigated to determine the functional significance of these signals. Paired burst sound production was associated exclusively with bottom feeding under low-light conditions, predominantly with evidence of associated conspecifics nearby suggesting that the sound likely serves either as a communicative signal to conspecifics, a signal to affect prey behaviour, or possibly both. This study provides additional evidence for individual variation and phenotypic plasticity of foraging behaviours in humpback whales and provides important evidence for the use of acoustic signals among foraging individuals in this species. W hy animals choose to cooperate, with animals from their own or other species, has long been a puzzle to evolutionary biologists 1-3 . More recently, these behaviours are increasingly being viewed as evidence of higher-level cognitive complexity in a wide variety of animal species 4 . Cooperative behaviours, particularly those associated with foraging, have been described in a wide diversity of taxonomic groups ranging from fish and reptiles 5 , to higher order mammalian groups including primates, carnivores, elephants, and cetaceans 6-9 .
Non-song social call bouts of migrating humpback whales
The Journal of the Acoustical Society of America, 2015
The use of stereotyped calls within structured bouts has been described for a number of species and may increase the information potential of call repertoires. Humpback whales produce a repertoire of social calls, although little is known about the complexity or function of these calls. In this study, digital acoustic tag recordings were used to investigate social call use within bouts, the use of bouts across different social contexts, and whether particular call type combinations were favored. Call order within bouts was investigated using call transition frequencies and information theory techniques. Call bouts were defined through analysis of inter-call intervals, as any calls within 3.9 s of each other. Bouts were produced significantly more when new whales joined a group compared to groups that did not change membership, and in groups containing multiple adults escorting a female and calf compared to adult only groups. Although social calls tended to be produced in bouts, ther...
Temporal stability and change in the social call repertoire of migrating humpback whales
The Journal of the Acoustical Society of America, 2013
Quantifying the stability of a species vocal repertoire is fundamental for further investigations into repertoire function and geographic variation. Changes to the repertoire of sounds used in the song displays of male humpback whales have been well studied. In contrast, little is known about the stability of this species' non-song vocal calls. The stability of the social call repertoire of east Australian humpback whales was investigated from 1997, 2003-2004, and 2008. Out of 46 qualitatively defined call types, 19 were classified as "song-unit calls" that tended to change with the song, and 15 were "inconsistent" and only found in one or two years. Twelve call types were "stable" and present in all years and were commonly produced (64.2% of calls). Stable calls tended to vary in some of the measured call parameters but there was no clear trend between years. This result could indicate that minor changes to calls are not permanent, but reflect individual differences in call production or the graded nature of calls within different social environments. This research has clearly identified stable calls in the call repertoire of humpback whales and while their function is not well understood, their stability suggests an important role in social interactions.
Biology Bulletin, 2013
We investigated the influence of the type of activity and the social context on the proportion of four different structural categories of stereotyped calls in the acoustic communication of Kamchatkan killer whales. Using generalized linear models, we described the dependence of each sound category on the type of activity, the number of killer whale pods and the presence of mixed pod groups. We found that the proportion of different sound categories depended on the number of pods and the presence of mixed pod groups, while the type of activity did not affect the proportion of sounds of different categories. Based on the observed dif ferences we suggest that biphonic and high frequency monophonic calls are mainly used as family and pod markers, and help to track the position of family members at long ranges, and low frequency monophonic calls are used as close range intra group signals to maintain contact between pod members in the conditions of limited underwater visibility.
The effects of vessel noise on the communication network of humpback whales
Royal Society Open Science, 2019
Humpback whales rely on acoustic communication to mediate social interactions. The distance to which these social signals propagate from the signaller defines its communication space, and therefore communication network (number of potential receivers). As humpback whales migrate along populated coastlines, they are likely to encounter noise from vessel traffic which will mask their social signals. Since no empirical data exist on baleen whale hearing, the consequences of this are usually assumed, being the modelled reduction in their communication space. Here, the communication space and network of migrating humpback whales was compared in increasing wind-dominated and vessel-dominated noise. Behavioural data on their social interactions were then used to inform these models. In typical wind noise, a signaller's communication space was estimated to extend to 4 km, which agreed with the maximum separation distance between groups that socially interacted. An increase in vessel noi...