Vocal Repertoire of Captive Capybara (Hydrochoerus hydrochaeris): Structure,Context and Function

In this work we describe the structure, behavioral context and functionality of the vocal repertoire of capybaras, a social Caviomorph rodent. Additionally, since territoriality is present in this species, we hypothesize the occurrence of vocal differences among social groups. We analyzed a total of 2069 calls emitted by 28 animals from three different social groups. The capybara’s repertoire is comprised by seven call types (whistle, cry, whine, squeal, bark, click and tooth‐chattering). The vocalizations were functionally categorized as contact, alarm, distress and agonistic calls considering their behavioral contexts. The click calls emitted by the adults of the three captive capybara groups were significantly different, confirming our hypothesis of social groups’ vocal differences. The richness of interactions mediated by vocalization in capybaras suggests that the species’ communication is an important mechanism to regulate social encounters and to alert members of the group about environmental cues.     

Dual Function of Chip Calls Depending on Changing Call Rate Related to Risk Level in Territorial Pairs of White‐Eared Ground‐Sparrows

Different mechanisms have been proposed for encoding information into vocalizations: variation of frequency or temporal characteristics, variation in the rate of vocalization production, and use of different vocalization types. We analyze the effect of rate variation on the dual function of chip calls (contact and alarm) produced by White‐eared Ground‐sparrows (Melozone leucotis). We conducted an acoustic playback experiment where we played back 1 min of four chip call rates (12, 36, 60, 84 calls/min). We measured the response of territorial pairs using behavioral responses, and fine structural features of calls produced in response to those playbacks. White‐eared Ground‐sparrows showed more intense behavioral responses to higher than lower call rate playbacks. Both individuals of the pair approached the source of the playback stimulus faster, produced the first vocalization faster, produced more vocalizations, and spent more time close to the stimulus in higher call rate than in lower call rate playbacks. Frequency and duration characteristics of calls (chip and tseet) were similar in response to all call rate playbacks. Our playback experiment elicited different intensity of behavioral responses, suggesting that risk‐based information is encoded in call rate. Our results suggest that variation in the rate of chip call production serves a dual function in this species; calls are used at lower rates for pair contact and at higher rates for alarm/mobbing signals.     

Vocal signature in capybara,Hydrochoerus hydrochaeris

Social groups of capybaras are stable and cohesive. The species’ vocal communication is complex and mediates social interaction. The click call is emitted in a variety of contexts by animals from all age groups, but differs among groups; its attributed function is to keep contact among animals. To evaluate the presence of individual characteristics in the click call of capybaras, we recorded the vocalizations emitted spontaneously by six adults kept either solitary or in groups. We selected and measured the acoustic parameters of 300 click call phrases, 50 per individual. The parameters were submitted to a discriminant function analysis that revealed a classification accuracy of 76.8 %. A General Linear Model analysis revealed significant differences among the six individuals, and post hoc results showed that differences between a given pair were different from those of any other pair. The acoustic parameters that most contributed to discriminate the individual calls were click interval duration and click duration, suggesting that temporal parameters are more important than frequency parameters for individuals’ discrimination. The findings of individual characteristics in the click calls indicate that these vocalizations can be used as vocal signatures during social interactions.     

Structural Variation in the Call of the Cory's Shearwater (Calonectris diomedea,Aves, Procellariidae)

The duet call, the principal vocalization of Cory's shearwaters, was structurally variable with different classes of call being apparent, corresponding to different individuals, sexes and populations. In playback tests, birds responded more frequently to the call of their mate than to other birds, birds of a given sex responded more frequently to playback calls of their own sex and birds of a given locality responded more frequently to birds of their own locality. We suggest some biological functions with respect to mating strategy, individual recognition, territorial behaviour, and population isolation.     

Vibrational Communication in Two Sympatric Species of Mantophasmatodea (Heelwalkers)

The communication via percussion of the abdomen on the substrate for species recognition and mate location of males and females of two sympatric species of the recently described insect order Mantophasmatodea (Heelwalkers) was investigated. Each sex produced a single and distinctive call. The female call consisted of repeated single pulses, whereas the more complex male call comprised repeated pulse trains. The calls of males and females of the two species were of similar general structure, but differed in most temporal characters such as pulse and pulse train repetition time. In behavioral playback experiments females reacted to the call of conspecific males by calling and decreasing locomotion. When stimulated with the call of the heterospecific, sympatric male, females showed no reaction. Males exhibited abdominal rubbing, high tapping rates, increased activity (both movement and active searching) as well as characteristic searching behavior at branch nodes, when presented with the conspecific female call. Being stimulated with the playback of the heterospecific female call and the conspecific male call respectively, males responded with less intense locomotor and searching behavior. The drumming behavior in the control situation (no playback) suggests that males sometimes call in the absence of other individuals.     

Evidence for acoustic communication in the parasitoid wasp Glyptapanteles flavicoxis

Females of the parasitoid wasp Glyptapanteles flavicoxis (Marsh) (Hymenoptera: Braconidae) deposit sex pheromone on substrate that elicits attraction and wing fanning in conspecific males. We tested the hypothesis that wing fanning sound induces a behavioral response from females which, in turn, affects the males’ orientation toward them. Females exposed to playback of the males’ wing fanning sound engaged in short flights, with sound characteristics different from those of the males’ wing fanning sound. In two‐choice bioassays, playback of the females’ flight sound attracted significantly more males than a silent control stimulus, and in combination with pheromone‐containing body extract of females it attracted more males than female body extract alone. Our data support the conclusion that the males’ wing fanning induces sound and visual reply signals from females that help males orient toward them.     

Phonotactic responses to vocalization in adult Mongolian gerbils (Meriones unguiculatus)

Mongolian gerbils have a rich repertoire of vocalization, with at least 13 distinct types of calls observed in a single colony. The purpose of this study was to compare the communicative value of these different call types in a standardized setting. Phonotactic behavior toward vocalizations delivered from loudspeakers was quantified by means of an eight-arm radial maze. Animals were observed to stay near the sound source for longer period of time when short bent-upward frequency-modulated (bUFM) calls, which are observed during seemingly friendly contact, were presented, while animals stayed significantly longer away from the speaker when arched FM (AFM) calls, which are produced by animals under severe physical stress, were presented. Our data show that an 8-arm radial maze can be used to study the function of Mongolian gerbil vocalization and suggest that both bUFM and AFM calls have communicative purposes, increasing the probability that recipient conspecifics approach or escape from the sound source, respectively.     

Singing in the Face of Danger: the Anomalous Type II Vocalization of the Splendid Fairy-Wren

Males of certain species of fairy-wrens (Aves: Maluridae) emit a unique vocalization, the Type II vocalization, in response to the calls of potential predators. We conducted field observations and playback experiments to identify the contexts in which the Type II vocalization is emitted by splendid fairy-wren ( Malurus splendens ) males, and to examine social and genetic factors that influence its occurrence. In field observations and controlled playback experiments, Type II vocalizations were elicited most consistently by calls of the predatory gray butcherbird ( Cracticus torquatus ). Some vocalizations from other avian species also elicited Type II vocalizations, and the majority of these were vocalizations from avian predators. Splendid fairy-wrens are cooperative breeders, and males that responded with Type II vocalizations to playbacks of butcherbird calls tended to be primary rather than secondary males, had larger cloacal protuberances, and were older than those that did not respond. In addition, secondary males that were sons of resident females were more likely than non-sons to respond with a Type II vocalization. In another playback experiment, females responded similarly to the Type I song and Type II vocalizations of their mates. Although the Type II vocalization is emitted primarily in response to predator calls, it is inconsistent with an alarm call explanation. Patterns of reproductive success among Type II calling males suggest that it does not function as an honest signal of male quality. At present, the function of the vocalization remains anomalous, but indirect fitness benefits may play a role in its explanation.     

Behavioral responses to species-specific warning calls in infant squirrel monkeys reared in social isolation

Six infant squirrel monkeys were reared in social isolation. They responded differentially to playbacks of two species-specific alarm calls. The reaction to the alarm peep, the warning call to bird predators, was a prompt flight to the mother surrogate and essentially resembled the respective behavior of mother-reared infants. The responses to yapping, the alarm call to terrestrial predators, were less clear-cut and habituated soon. However, when yapping was played back in connection with the presentation of a reference object, both subjects tested in this way clearly avoided the object and preferred contact with the mother surrogate while they thoroughly explored an object presented with a control tone. From this it can be concluded that the perception of both alarm calls is innate. In addition, the method of behavior-contingent playback of vocalizations simulates the learning process by which the visual perception of terrestrial predators of the habitat is acquired.     

Squirrel monkey chuck call: vocal response to playback chucks based on acoustic structure and affiliative relationship with the caller

Adult female squirrel monkeys (genus Saimiri) that are socially familiar often exchange the chuck vocalization, which differs acoustically across individuals. We used behavioral observations, vocalization playback experiments, and analysis of the acoustic properties of vocalizations to investigate the effect of caller identity and acoustic structure on vocal response to playback chucks in two all-female social groups (n=10 females). Females were most likely to respond with a chuck to the playback chucks of their closely affiliated partners compared to those of nonaffiliated group members. This shows for the first time that the chuck stimulus alone is sufficient to elicit a chuck response from a female's affiliated partner. Additionally, females responded with a chuck mostly to familiar playback chucks from their own group and least to playbacks of silent controls. Unfamiliar playback chucks from the same species and a different squirrel monkey species elicited chuck responses intermediate between familiar chucks and silent controls. Post-hoc discriminant function analyses provide preliminary evidence that females are most likely to respond to unfamiliar chucks when those chucks are close in acoustic structure to familiar chucks from their own social group. These results provide a provisional explanation for error in the squirrel monkey signal processing system, in which unfamiliar chucks never heard before nevertheless elicit a chuck response if they are similar in acoustic structure to familiar group chucks.     

Do newborn vocalizations affect the behavioral and hormonal responses of nonreproductive male common marmosets (Callithrix jacchus)?

Parental care in mammals is influenced by sensory stimuli from infants, such as sight and sound, and by changes in the hormone levels of caretakers. To determine the responsiveness of common marmoset (Callithrix jacchus) adult males with and without previous experience in caretaking to newborn sensory cues, we exposed twelve males to infant vocalization recordings and assessed their hormonal and behavioral responses. Males were placed in the testing cage for 10 min under two conditions: (a) control condition (exposure to adult conspecific vocalization recordings), and (b) experimental condition (exposure to infant vocalization recordings). We recorded the frequency of approach towards the sound source, the time spent near it and locomotion frequency of males in the cage under both conditions. Blood samples were collected after each test for cortisol, measured by the enzyme immunoassay method. Infant vocalization affects the behavioral and hormonal responses of non-reproductive male common marmosets. All males approached and spent more time near the sound source and showed an increase in locomotion during infant vocalization exposure compared to the control condition. Successive exposure to infant vocalization increased the responsiveness in inexperienced males. Cortisol levels were significantly higher following infant vocalization exposure compared to the control condition. These findings support the assumption that sound stimuli from the newborn are critical in initiating and maintaining caretaker responsiveness and that cortisol seems to be important for alertness to sensory stimuli, modulating their motivation to interact with infants.     

Response of Captive Raptors to Avian Mobbing Calls: the Roles of Mobber Size and Raptor Experience

The ‘move on’ hypothesis for avian mobbing proposes that mobbing induces stress in potential predators, thereby provoking them into moving elsewhere. We tested whether mobbing is stress inducing by subjecting captive owls, hawks, and falcons to the mobbing calls of four species of co‐occurring passerine birds that vary considerably in body size. Test subjects comprised 15 individuals of seven species of birds of prey that were housed at a wildlife rehabilitation center in northwestern Pennsylvania, USA. Playback treatments included mobbing calls of the black‐capped chickadee (Poecile atricapillus), blue‐headed vireo (Vireo solitarius), blue jay (Cyanocitta cristata), and American crow (Corvus brachyrhynchos), which vary in size from 12 g (chickadee) to 500 g (crow). A non‐mobbing vocalization (song of the black‐capped chickadee) was included in the playback treatments as a control. Playback treatment produced pronounced effects on three behavioral indicators of probable stress: head orientation toward the playback speaker, raising of feathers or spreading of wings, and changing of perch positions. Test subjects responded more vigorously to mobbing calls of the large passerines (jays and crows) than to those of the smaller passerines (chickadees and vireos). In addition, raptors that had entered the rehabilitation facility as adults generally responded more vigorously to the mobbing calls of jays and crows than did naive individuals that had entered the facility as fledglings or young juveniles. Our results are therefore consistent with the ‘move on’ hypothesis and suggest (1) that the mobbing calls of large passerines are more effective in provoking stress and altering the behavior of potential predators than are the mobbing calls of small passerines and (2) that a raptor's previous experience with mobbing in the wild can exaggerate the strength of its response, particularly to the mobbing calls of large passerines.     

Pair Duets in the Yellow-Naped Amazon (Psittaciformes: Amazona auropalliata): Responses to Playbacks of Different Dialects

Yellow-naped amazons, Amazona auropalliata , have regional dialects in which several functional classes of vocalization, including contact calls and pair duets, change their acoustic structure at the same geographic boundaries. Here we examine the responses of 11 pairs of yellow-naped amazons to playbacks of duets from other pairs nesting near the same roost, other roosts within the same dialect, and roosts in foreign dialect areas. Overall, pairs responded more strongly to duets from their own dialect than to those of the foreign dialect. Pairs responded to both treatments from their own dialect (local same dialect and distant same dialect) with movement towards the broadcasting loudspeaker and more rarely with squeals, a vocalization typically observed only in the context of aggressive chases. These aggressive responses were never observed during playbacks of the foreign dialect treatment or congeneric controls. There were no differences among treatments in the incidence of contact calls or pair duets. A similar pattern of stronger aggressive responses to local than to foreign dialects has been found in a wide range of oscine songbirds. The results of the present experiment suggest that a general function may underlie this behavioral response both in oscines and in other bird taxa with vocal learning.     

Vocal exchanges of signature whistles in bottlenose dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>)

Bottlenose dolphins (Tursiops truncatus) produce individually distinctive vocalizations—referred to as “signature whistles”—that are thought to function as an individual and conspecific recognition system for maintenance of consistent contact between individuals. Observations and playback experiments were conducted at aquariums to study these whistle–vocal exchanges in bottlenose dolphins. Temporal patterns of vocalization were examined by analyzing the intercall intervals between two consecutive whistles. When a second individual produced a call that was different from the first individual’s vocalization, most of these calls were shorter than 1 s. However, when two consecutive calls were produced by the same individual, the second call rarely occurred within 1 s of the first. These results suggest that a second whistle may be produced by a different caller in response to the first whistle; however, in the case of an absence of a response, the first caller is likely to give further whistles. The results of this acoustic analysis show that the dolphins used in this study mostly used signature whistles during the recorded vocal exchanges.     

Vocal-tract filtering by lingual articulation in a parrot

Human speech and bird vocalization are complex communicative behaviors with notable similarities in development and underlying mechanisms. However, there is an important difference between humans and birds in the way vocal complexity is generally produced. Human speech originates from independent modulatory actions of a sound source, e.g., the vibrating vocal folds, and an acoustic filter, formed by the resonances of the vocal tract (formants). Modulation in bird vocalization, in contrast, is thought to originate predominantly from the sound source, whereas the role of the resonance filter is only subsidiary in emphasizing the complex time-frequency patterns of the source (e.g., but see ). However, it has been suggested that, analogous to human speech production, tongue movements observed in parrot vocalizations modulate formant characteristics independently from the vocal source. As yet, direct evidence of such a causal relationship is lacking. In five Monk parakeets, Myiopsitta monachus, we replaced the vocal source, the syrinx, with a small speaker that generated a broad-band sound, and we measured the effects of tongue placement on the sound emitted from the beak. The results show that tongue movements cause significant frequency changes in two formants and cause amplitude changes in all four formants present between 0.5 and 10 kHz. We suggest that lingual articulation may thus in part explain the well-known ability of parrots to mimic human speech, and, even more intriguingly, may also underlie a speech-like formant system in natural parrot vocalizations.     

Is there variation in the response to contact call playbacks across the hybrid zone of the parrot Platycercus elegans?

Learned vocal signals could be important in the formation of prezygotic isolation between two hybridising taxa. This study examined whether vocal variation in the parrot Platycercus elegans facilitates the separation of individuals from two subspecies, P. e. elegans (CR) and P. e. flaveolus (YR). CR and YR have very different plumage coloration, respectively deep crimson and pale yellow, but hybridise where they meet creating an intermediate population (WS). In a factorial design playback experiment, we conducted 108 playback trials on three focal populations (YR, WS, CR), in and around this area of hybridisation, to test if they respond differently to contact calls from their own or another population. We also analysed whether differences in acoustic variables of the stimulus calls predicted the response to the call. We did not find any indication that individuals from the three focal populations responded differently to calls sampled from their own or another subspecies. We did find an effect of two of the five acoustic variables that we used to describe and classify contact calls from the three source populations. Specifically, duration of the stimulus call positively affected the response from individuals from WS and negatively the response from CR, and CR responded more to stimulus calls with a lower peak frequency. Overall, we found no indication that acoustic variation in contact calls on a subspecies level is involved in maintaining plumage colour differences between P. e. elegans and P. e. flaveolus subspecies.     

Effects of contextual and social variables on contact call production in free-ranging ringtailed lemurs (Lemur catta)

Ringtailed lemurs (Lemur catta)often emit a characteristic vocalization when resting as a troop. This “meow call” is believed to serve an intragroup contact function. I investigated the effects of behavioral context and proximity on call production and acoustic features of the vocalization in a free-ranging troop in the Berenty Reserve, Madagascar. When group members were dispersed, the meow call was given frequently, and the acoustic features of the call probably increased the locatability of the emitter. I evaluated social relationships among the troop members from grooming interactions and spacing data. I also studied the call exchange network among the troop members, the results of which indicate that calls are exchanged between the two subgroups of females, which they connect.     

Investigating Empathy-Like Responding to Conspecifics’ Distress in Pet Dogs

Empathy covers a wide range of phenomena varying according to the degree of cognitive complexity involved; ranging from emotional contagion, defined as the sharing of others’ emotional states, to sympathetic concern requiring animals to have an appraisal of the others’ situation and showing concern-like behaviors. While most studies have investigated how animals reacted in response to conspecifics’ distress, dogs so far have mainly been targeted to examine cross-species empathic responses. To investigate whether dogs would respond with empathy-like behavior also to conspecifics, we adopted a playback method using conspecifics’ vocalizations (whines) recorded during a distressful event as well as control sounds. Our subjects were first exposed to a playback phase where they were subjected either to a control sound, a familiar whine (from their familiar partner) or a stranger whine stimulus (from a stranger dog), and then a reunion phase where the familiar partner entered the room. When exposed to whines, dogs showed a higher behavioral alertness and exhibited more stress-related behaviors compared to when exposed to acoustically similar control sounds. Moreover, they demonstrated more comfort-offering behaviors toward their familiar partners following whine playbacks than after control stimuli. Furthermore, when looking at the first session, this comfort offering was biased towards the familiar partner when subjects were previously exposed to the familiar compared to the stranger whines. Finally, familiar whine stimuli tended to maintain higher cortisol levels while stranger whines did not. To our knowledge, these results are the first to suggest that dogs can experience and demonstrate “empathic-like” responses to conspecifics’ distress-calls.     

四川山鹧鸪繁殖期的鸣声行为特征

2005年4—12月在四川老君山自然保护区,通过计算机声谱分析技术,对四川山鹧鸪(Arborophilarufipectus)雄性的鸣声行为特征进行了研究,其结果表明,雄性单音节鸣声出现在啼叫、保护领域和求偶中,这些鸣声持续时间差异明显,主峰值差异不明显;雄性双音节鸣声出现在啼叫、保护领域、竞争雌体和求偶中,这些鸣声第一音节时间、第二音节时间、音节间隔时间和主峰值差异极显著,全句时间差异不明显;雄性多音节鸣声出现在保护领域、警戒和惊吓中。雄性亚成体多音节鸣声出现在惊吓和警戒中;雄性成体和亚成体警戒鸣叫的音节持续时间、音节间隔时间和主峰值差异均不明显,全句持续时间差异明显;雄性亚成体和雄性成体的惊吓鸣叫音节持续时间、音节间隔时间、全句持续时间和主峰值差异均不明显。四川山鹧鸪表现出的各种鸣声行为是为了保护配偶和防止天敌,使该种群更好地繁衍。     

Individuality,kin similarity and experimental playback of contact calls in cooperatively breeding riflemen

Riflemen/tītipounamu (Acanthisitta chloris) are kin-based cooperatively breeding birds, which appear able to recognise their relatives. Here, we investigate the potential for vocalisations to act as recognition cues in riflemen. We identified an appropriate contact call and recorded it at the nest from 19 adult riflemen. Measurements of call characteristics were individually repeatable. In addition, call similarity was significantly correlated with relatedness among all birds and among males. Thus, in principle, these contact calls contain sufficient information for individual recognition of familiar kin, and some assessment of relatedness between unfamiliar birds. To test whether riflemen responded differently to calls of kin, we broadcast calls of relatives and non-relatives as separate treatments in a playback experiment. Focal birds rarely responded aggressively or affiliatively, and their tendency to do so was unrelated to treatment. We conclude that zip calls are suitable kin recognition cues, but whether they are used as such remains unknown.