Vocal Repertoire of Cebus capucinus: Acoustic Structure, Context, and Usage

Researchers studying nonhuman primate vocal repertoires suggest that convergent environmental, social, and motivational factors account for intra- and interspecific vocal variation. We provide a detailed overview of the vocal repertoire of white-faced capuchins, including acoustic analyses and contextual information of vocal production and vocal usage by different age-sex classes in social interactions. The repertoire is a mixture of graded and discrete vocalizations. In addition, there is general support for structural variation in vocalizations with changes in arousal level. We also identified several combined vocalizations, which might represent variable underlying motivations. Lastly, by including data on the social contexts and production of vocalizations by different age-sex classes, we provide preliminary information about the function of vocalizations in social interactions for individuals of different rank, age, and sex. Future studies are necessary to explore the function of combined vocalizations and how the social function of vocalizations relate to their acoustic structure, because social use of vocalizations may play an important role in shaping vocal evolution.     

Acoustic Analysis of Signals in Mammals

Spectral-prosodic characteristics of signals were analyzed synchronously with the main frequency for 32 mammals and one reptile using a KAZ-01 complex sound analyzer. The method of phoneme analysis was adapted for analysis of the signals. The main features of signaling in mammals have been revealed, which differed from those in birds and humans: low frequency range, low fundamental frequency, small number of local maxima, small frequency distance between them, and a significant amount of local maxima with zero energy.     

Efficiency and Significance of Multiple Vocal Signals in Sibling Competition

Animals can compete for resources by displaying various acoustic signals that may differentially affect the outcome of competition. We propose the hypothesis that the most efficient signal to deter opponents should be the one that most honestly reveals motivation to compete. We tested this hypothesis in the barn owl (Tyto alba) in which nestlings produce more calls of longer duration than siblings to compete for priority access to the indivisible prey item their parents will deliver next. Because nestlings increase call rate to a larger extent than call duration when they become hungrier, call rate would signal more accurately hunger level. This leads us to propose three predictions. First, a high number of calls should be more efficient in deterring siblings to compete than long calls. Second, the rate at which an individual calls should be more sensitive to variation in the intensity of the sibling vocal competition than the duration of its calls. Third, call rate should influence competitors’ vocalization for a longer period of time than call duration. To test these three predictions we performed playback experiments by broadcasting to singleton nestlings calls of varying durations and at different rates. According to the first prediction, singleton nestlings became less vocal to a larger extent when we broadcasted more calls compared to longer calls. In line with the second prediction, nestlings reduced vocalization rate to a larger extent than call duration when we broadcasted more or longer calls. Finally, call rate had a longer influence on opponent’s vocal behavior than call duration. Young animals thus actively and differentially use multiple signaling components to compete with their siblings over parental resources.     

Vocal Tract Morphology Determines Species-Specific Features in Vocal Signals of Lemurs (Eulemur)

The source-filter theory describes vocal production as a two-stage process involving the generation of a sound source, with its own spectral structure, which is then filtered by the resonant properties of the vocal tract. This theory has been successfully applied to the study of animal vocal signals since the 1990s. As an extension, models reproducing vocal tract resonance can be used to reproduce formant patterns and to understand the role of vocal tract filtering in nonhuman vocalizations. We studied three congeneric lemur species —Eulemur fulvus, E. macaco, E. rubriventer— using morphological measurements to build computational models of the vocal tract to estimate formants, and acoustic analysis to measure formants from natural calls. We focused on call types emitted through the nose, without apparent articulation. On the basis of anatomical measurements, we modeled the vocal tract of each species as a series of concatenated tubes, with a cross-sectional area that changed along the tract to approximate the morphology of the larynx, the nasopharyngeal cavity, the nasal chambers, and the nostrils. For each species, we calculated the resonance frequencies in 2500 randomly generated vocal tracts, in which we simulated intraspecific length and size variation. Formant location and spacing showed significant species-specific differences determined by the length of the vocal tract. We then measured formants of a set of nasal vocalizations (“grunts”) recorded from captive lemurs of the same species. We found species-specific differences in the natural calls. This is the first evidence that morphology of the vocal tract is relevant in generating filter-related acoustic cues that potentially provide receivers with information about the species of the emitter.     

Assessing the Patterns of Evolution in Anuran Vocal Sexual Signals

Many animal species have evolved signalling traits to mediate various intra-specific interactions. Signals are particularly important for inter-sexual selection, where females use male signalling traits to select mates. Female preferences are therefore a major selective force in the evolution of these male signals, and these preferences can facilitate rapid changes in these traits in an evolutionary timeframe. This introduction of high levels of variation in inter-sexual signals may overshadow any phylogenetic patterns present. Such shadowing effects, however, should be dependant on the characteristics of traits (e.g. morphological, physiological and behavioural). Using male advertisement calls from 72 species of anuran amphibians, we tested the levels of phylogenetic signal present for a variety of call features in relation to trait types, and for calls as whole units using phylogenetic principal components analysis. We found that most call features displayed some level of phylogenetic autocorrelation (or signal), with traits that are dependent on morphology having much stronger phylogenetic signals than those based on behaviour. In addition, when calls were analysed as whole units, closely related species were found to be similar to each other, indicating that phylogenetic patterns had not been cancelled out by selection via female preferences. We suggest that signal functions, such as indicating male quality (e.g. mediated by body size) to potential mates, may place constraints on the amount of variation that can be introduced by female preferences. More research, particularly studies on other taxa, will be required to elucidate whether the patterns found in anurans are general across the animal kingdom.     

Female Preferences for Male Vocal and Facial Masculinity in Videos

Vocal and facial masculinity are cues to underlying testosterone in men and influence women’s mate preferences. Consistent with the proposal that facial and vocal masculinity signal common information about men, prior work has revealed correlated female preferences for male facial and vocal masculinity. Previous studies have assessed women’s preferences for male facial and vocal masculinity by presenting faces and voices independently and using static face stimuli. By contrast, here we presented women with short video clips in which male faces and voices were simultaneously manipulated in masculinity. We found that women who preferred masculine faces also preferred masculine voices. Furthermore, women whose faces were rated as relatively more attractive preferred both facial and vocal masculinity more than did women whose faces were rated as less attractive. These findings complement other evidence for cross‐modal masculinity preferences among women and demonstrate that preferences observed in studies using still images and/or independently presented vocal stimuli are also observed when dynamic faces and voices are displayed simultaneously in video format.     

Acoustic Features of Female Chacma Baboon Barks

We studied variation in the loud barks of free-ranging female chacma baboons ( Papio cynocephalus ursinus ) with respect to context, predator type, and individuality over an 18-month period in the Moremi Game Reserve, Botswana. To examine acoustic differences in relation to these variables, we extracted a suite of acoustic parameters from digitized calls and applied discriminant function analyses. The barks constitute a graded continuum, ranging from a tonal, harmonically rich call into a call with a more noisy, harsh structure. Tonal barks are typically given when the signaler is at risk of losing contact with the group or when a mother and infant have become separated (contact barks). The harsher variants are given in response to large predators (alarm barks). However, there are also intermediate forms between the two subtypes which may occur in both situations. This finding is not due to an overlap of individuals' distinct distributions but can be replicated within individuals. Within the alarm bark category, there are significant differences between calls given in response to mammalian carnivores and those given in response to crocodiles. Again, there are intermediate variants. Both alarm call types are equally different from contact barks, indicating that the calls vary along different dimensions. Finally, there are consistent, significant differences among different individuals' calls. However, individual identity in one call type cannot directly be inferred from knowledge of the individuals' call characteristics in the other. In sum, the barks of female baboons potentially provide rich information to the recipients of these signals. The extent to which baboons discriminate between alarm and contact barks, and classify calls according to context and/or acoustic similarity will be described in a subsequent paper.     

Acoustic Behaviour of Birds and Mammals in the Predator Context; I. Factors Affecting the Structure of Alarm Signals. II. The Functional Significance and Evolution of Alarm Signals

I. 7 vocalizations emitted in the predator context are defined in terms of their function. The physical and physiological constraints on the evolution of the physical structure of alarm calls with respect to detectability and localizability are discussed. Detection of various calls depends on signal amplitude, environmental attenuation, signal-to-noise ratio, discrimination of the receiver against background noise, and absolute auditory sensitivity of the receiver. The combined effect of these factors is discussed for an exemplary predator-prey system, in which the hearing of both, predator and prey is known. Localizability of an alarm call is determined by its frequency, bandwidth, and possibly its amplitude relative to the auditory threshold of the receiver. Crude differentiation between localizable and non-localizable signals is not possible, and localizability of particular sounds varies between species. In some cases the question of detectability may render the problem of localizability unimportant. Besides detectability and localizability, other factors such as the acoustic background formed by the alarm calls of sympatric species and by the species' own repertoire of calls are discussed. II. Requisite conditions and available evidence for the evolution of alarm calls through individual selection and kin selection are described. Five types of alarm calls are discussed individually:

• 1 The occurrence of mobbing calls indicates that a major function of these calls is predator deterrence (“move on”), although the calls also alert other prey and promote cultural transmission of the predator's characteristics.
• 2 Alarm calls associated with evasive actions of the prey cause the predator to give up the hunt or diminish its hunting success by warning other prey, which only in some cases are closely related to the caller.
• 3 Distress calls of a seized prey either attract other prey which then mob the predator, or attract other predators, which presumably attack the first predator. In both cases the chances to escape are enhanced because the predator's attention is diverted.
• 4 Defence calls are used to threaten a predator. These calls often mimic sounds of other predators.
• 5 Distraction calls may enhance the effect of distraction display.

Although the different functions of various alarm calls are treated individually, certain of the calls may have more than one function and may be employed in nonpredator contexts as well.     

Responses of Male and Female Black Grouse to Male Vocal Display

The evolution of leks may be explained by several hypotheses. The ‘female preference’ hypothesis, which states that females favour males that have aggregated, has recently gained some empirical support. Low-quality, unattractive males may, however, settle near attractive males, as predicted by the ‘hotshot’ hypothesis. We tested whether black grouse Tetrao tetrix females use auditory cues to find the preferred leks, and whether males respond to vocal display emitted on leks. We conducted a playback experiment with male vocal display (rookooing) on leks, where the visiting females and displaying males were counted. The number of males tended to increase more on playback leks. Specifically, the number of 1-year-old males was greater on playback sites than on control sites. Also, the number of females, in relation to the lek size before the start of the experiment tended to increase. In addition, we used aviary playback trials to test whether females distinguish between single-male and multi-male displays. In a choice test, females showed greater preference for the ‘multi-male’ tape. The tendency for increased male numbers on playback leks resulted from increased visits of young, mobile males which were attracted to leks that they perceived to be large. This suggests a ‘hotshot’-type mechanism in the settlement of young males. Because females also responded to the supplemented auditory advertisement, or directly to the increased number of males, the ‘female preference’ hypothesis is also supported. Females may, at least in part, base their decision of which lek to visit on auditory cues, but visual contact to males may be also needed.     

Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu) in Captivity: Sound Structure,Context and Vocal Activity

Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish^-1 h^-1) with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas.     

Acoustic Signals in Mouse Maternal Behavior: Retrieving and Cannibalism

The purpose of this study was to show that juvenile acoustic signals are not essential prerequisites for inhibiting parental aggression or for eliciting maternal care. This was demonstrated by comparing the behavior of Rb-3 and GFF+/+ female mice with normal audition and that of a deaf mutant GFF dn/dn. 243 ♀♀ and 609 litters were used to measure cannibalism and 54 ♀♀ to measure speed of retrieval. Neither rate of cannibalism nor speed of retrieval were modified by deafness, thus verifying the proposed hypothesis.     

Selective Responsiveness to Long-Range Acoustic Signals in Insects and Anurans

SYNOPSIS. Insects and anurans show various patterns of selectiveresponsiveness to playbacks of natural and synthetic sounds.Preferences and tuning of the auditory system most often matchone or more strongly emphasized frequency components in long-range,mate-attracting signals typical of conspecific individuals,but exceptions, in which frequencies lower or higher than themean are preferred, occur in some species. In some insects themost preferred frequencies may correspond to regions that maximizelocalizability of signals rather than regions of maximum sensitivity.Patterns of preference for fine-temporal properties are typicallystabilizing within a population; females prefer values nearthe mean and few males produce calls with values that deviatesufficiently to make them less attractive than calls with averagevalues. Preferences for gross temporal properties {e.g., therate and duration of signaling) are usually highly directional,with much higher than mean values preferred. In anurans, callrate is a better predictor of male mating success than dominantfrequency. Nevertheless, a variety of factors, especially close-rangeassessments that are common in insects, may modify or negatethe advantages of producing long-range signals of high relativeattractiveness. The evolutionary consequences of selective responsivenessin anurans and insects are discussed     

Dingo Howls: The Content and Efficacy of a Long‐Range Vocal Signal

Signals are shaped through selective pressures impacting their information content (i.e. ‘what’ is conveyed) and their efficacy (i.e. ‘how’ is it conveyed). In the case of long‐range communication, a signal's structure should both convey information and allow for detection and discrimination despite the effects of environmental variability during propagation. Canid howls are an ideal example of a long‐range communication signal, although research has mostly focused on the relationships between howls’ acoustic characteristics and their potential information content in wolves, Canis lupus spp., and coyotes, Canis latrans. In this study, we quantified these relationships in another canid, the dingo, Canis familiaris dingo, to determine how their howls compare to that of other wild canids. We found that dingoes’ howls are individually distinctive and may convey gender cues. Playback experiments indicate that dingoes can perform class‐level recognition of familiar and unfamiliar individuals on the basis of vocalizations alone. These results mirror findings for other wild canids such as wolves and coyotes. Lastly, propagation experiments demonstrate that this signal's structure can permit long‐distance detectability and discriminability. We discuss our results in relation to the putative functions of canid howls and propose avenues for future research.     

大杜鹃雌鸟鸣声的日节律

本文描述了三个地区大杜鹃(Cuculus canorus)雌鸟鸣声的日节律。通过在北京野鸭湖湿地公园(2017年5月7日至7月8日)、辽宁辽河口自然保护区(2018年6月28日至7月29日)和吉林大岗子林场(2018年5月17日至7月10日)分别布设自动录音机10台、10台和8台,连续记录繁殖季大杜鹃的鸣声。共录到2 777次大杜鹃雌鸟的鸣叫。其中,1 431次来自北京野鸭湖湿地公园,1 222次来自辽宁辽河口自然保护区,124次来自吉林大岗子林场。野鸭湖湿地公园和辽河口自然保护区的大杜鹃雌鸟在日出时段出现鸣叫的高峰,而大岗子林场的大杜鹃在日出和日落时段各有一个鸣叫的高峰。通过比较大杜鹃雌鸟鸣声的日节律和大杜鹃产卵时间的日节律,本研究认为在上述地区大杜鹃雌鸟鸣叫的功能更可能是宣示领域和吸引异性,而非恐吓宿主。本研究有助于进一步了解大杜鹃雌鸟鸣声的功能。     

Ecological and Social Factors Affecting the Vocal Behavior of Adult Female Squirrel Monkeys

Focal recordings of the vocalizations of squirrel monkeys, Saimiri sciureus, occupying an undisturbed Peruvian habitat were collected to evaluate the importance of both the ecological and social functions of female vocal behavior. The rates and sequences of six call types were examined by context: single, double, and multiple chuck, peep, tweet, and tweet-chuck. In contrast to laboratory studies, our findings emphasize the primacy of ecological functions in the wild, where calling permits females to operate as a convoy of spatially separated individuals in an arboreal habitat where visual contact is limited. Chuck calls are probably best interpreted as contact calls. The rate of chucks and tweet-chucks increased when the nearest adult female was > 5 m away. However, call production did not predict a change in the spatial separation between a female and her nearest adult female. During travel, the rate of single and double chucks was greater and the rate of multiple chucks was reduced. No direct relationship was found between foraging activities and vocal behavior. Although secondary, social factors did have a subtle effect on vocal behavior: the larger the social alliance of a female, the lower the rate and repetitiveness of her chuck vocalizations. We also consider the role of variations in vocalization rates among primates and the differing conclusions of field and captive studies of squirrel monkey vocal behavior.     

Female Social Feedback Reveals Non-imitative Mechanisms of Vocal Learning in Zebra Finches

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From Sender to Receiver: Propagation and Environmental Effects on Acoustic Signals

SYNOPSIS. Acoustic signals transmitted over large distancesdiffer significantly from those emitted by the signaler. Acousticsignals degrade in amplitude, spectral and temporal structureas they propagate through theenvironment. A great deal of workon acoustic communication is aimed at understanding the selectiveforces imposed by the environment on animal signals. I willdiscuss the physical constraints the environment puts on acousticcommunication, and then discuss similarities in communicationby anurans and insects that relate these environmental constraintsto their signaling systems. Lastly, I show how changes in signalsduring propagation relate to changes in signal perception duringphonotaxis, and thus, how propagation relates to mate choiceand sexual selection