Troop-specific responses to long calls of isolated tamarins (Saguinus mystax)

Recently captured moustached tamarins (Saguinus mystax) were briefly separated from other members of their troop. Most separated animals emitted long calls that were, in general, similar in acoustic structure to those of sympatric tamarin species while retaining species distinctiveness. Individual differences also appeared in call structure. The long calls of a separated animal were responded to almost entirely by members of the animal's own troop rather than by other troops, and reciprocal calling occurred among troop members significantly more often than expected by chance. Although there was no evidence of troop-specific call structure or dialect, there were troop-specific responses to the calls of separated tamarins. This response implies the existence of a stable and integrated troop structure that allows troop members to learn and to respond to the individual specific features of each troop member's calls.     

The influence of age and sex on the vocal repertoire of the Antillean manatee (Trichechus manatus manatus) and their responses to call playback

Limited information is available regarding the acoustic communication of Antillean manatees, however, studies have shown that other manatee taxa produce vocalizations as a method of individual recognition and communication. Here, the acoustic signals of 15 Antillean manatees in captivity were recorded, aiming to (1) describe their acoustic repertoire, (2) investigate the influence of sex and age on vocalization, and (3) examine manatee responses to call playback. Six acoustic signals ranging in mean fundamental frequencies from 0.64 kHz to 5.23 kHz were identified: squeaks and screeches were common to adult males, adult females, and juveniles; trills were common to adult males and females; whines were specific to males; creaks were specific to females; and rubbing was specific to juveniles. The structure of squeak vocalizations was significantly different between age and sex classes and screech structure was significantly different between age classes. Squeaks and screeches produced by juveniles had higher frequencies of maximum energy when compared to those produced by adult males and females. A significant increase in the vocalization rate following vocalization playbacks was found for all three age/sex groups. Our results introduce the potential of using acoustic signals in identifying and noninvasively monitoring manatees in the wild in Brazil.     

Primate phonation: Anterior cingulate lesion effects on response rate and acoustical structure

Four juvenile rhesus monkeys (Macaca mulatta) that were conditioned to emit a discriminative vocal response underwent unilateral and bilateral lesions of anterior cingulate gyrus in stepwise sequence. Pre- and post-lesion measures of vocal response rate and acoustical features (call duration, amplitude, and fundamental frequency) were obtained for the conditioned task and for vocalization in the home colony (spontaneous vocalization). Unilateral lesions produced little consistent change in spontaneous “coo” vocalization rate and call duration. Conditioned vocalization of the monkeys exhibited no significant change in rate at this stage, although call duration was reduced significantly. Bilateral lesions produced no further modifications in acoustic properties of spontaneous calls, while the vocal rate decreased slightly. Conditioned calls were not significantly altered in acoustic features at this stage, although the discriminative vocalization rate was significantly decreased for all monkeys. The results indicate limited control over vocal motor systems by anterior cingulate cortex, while suggesting that this region participates in initiation of voluntary phonation.     

Human Classification of Context-Related Vocalizations Emitted by Familiar And Unfamiliar Domestic Cats: An Exploratory Study

ABSTRACT

Previous research has shown that human classification of contextspecific domestic cat “meow” vocalizations is relatively poor, although improves with experience and/or general affinity to cats. To investigate whether such classification further improves when recipients (humans) of the vocalizations reside with the vocalizing animal (cat), cat owners (n=10) were asked to listen to eight audio recordings of a single meow (4 from their own cat and 4 from an unfamiliar cat) produced during one of four possible contexts, and identify the context in which each meow was emitted. Contexts comprised food preparation, food-withholding, negotiating a barrier, and attention solicitation. In addition, participants were asked to rate 20 meow vocalizations (produced by unfamiliar cats in the four contexts) on scales measuring pleasantness and urgency, in order to investigate whether participants reached consensus on the emotional content of the vocalizations. Successful identification of both the context and the hypothesized emotional content of the vocalization would comprise the first steps in our understanding of whether human-directed cat “meow” vocalizations are fully advantageous. Forty percent of the participants identified the correct contexts at a level greater than chance when the vocalizations belonged to their own cat. However, no participants performed above chance when vocalizations belonged to an unfamiliar cat. Participants’ urgency ratings were not significantly influenced by the context in which the vocalization was produced. Pleasantness ratings, however, were significantly higher for the context of negotiating a barrier in comparison with attention solicitation. These results suggest that the domestic cat, as a species, does not have a context-specific repertoire of human-directed vocalizations. Successful context classification of cat meows however, was possible for some owners. Whether such success was due to individual learning ability or recognition of hypothesized emotional content of the call requires further investigation.     

The study of vocal communication of wild mandrills in Cameroon in relation to their social structure

The vocal repertoire of the mandrill (Mandrillus sphinx), a forest living baboon, is described, and their vocal communication analyzed quantitatively. Although the vocal repertoire of mandrills corresponds well to that of savanna living baboons,Papio, some characteristics differed, such as the development of long-distance calls and differentiation of vocalizations between age-sex classes. Vocal communication within a group was closely related to changes in the spatial distribution of group members, and the two most common vocalizations, crowing and 2PG, appear to function as contact calls. Based on the wide dispersion of food trees, a group of mandrills divided into several feeding groups (subgroups). The two types of contact call were given in different and in some senses complementary contexts, and helped to facilitate and maintain group integration. According to their acoustic structure, these calls are long distance calls. Influenced by the high-level of attenuation of vocalization on the forest floor, the mandrill has developed them as contact calls, instead of using the contact “grunt,” which is common to the savanna living baboons. Comparing the patterns of vocal exchanges of mandrills with those of gelada and hamadryas baboons which have a multi-levelled society, the social structure of the mandrill is discussed. From the analysis of the spatial distribution of vocal emission, a number of clusters of vocalizations were obtained. These clusters correspond to subgroups. The frequent female-female and female-male vocal exchange between subgroups of mandrills suggest that the relationships between subgroups are less closed than between the one-male units of gelada and hamadryas baboons. Furthermore some of these clusters include more than two vocalizing adult males, while in other clusters there are no vocalizing adult males. Thus, the social structure of mandrills is suggested to be multi-male rather than a multilevelled type. The absence of contact calls specific for short distance and the functional replacement of the grunting of all group members by persistent emission of a loud call (2PG) by usually just one adult male suggests that the social structure of mandrills is not exactly equivalent to that of the multimale troop of savanna living baboons. Usually the use of 2PG is monopolized by one adult male travelling in the rear part of the group. Such monopolization of 2PG emission and the pattern of 2PG-2PG or 2PG-roar exchanges by adult males in some cases indicate the existence of strong dominance relationships among adult males, and especially the existence of a leader male within a multi-male group of mandrills.     

THE VOCAL REPERTOIRE OF THE GREY CROWNED CRANE BALEARICA REGULORUM GIBBERICEPS. II: THE UNISON CALL

ABSTRACT

This paper presents the acoustic features and the behavioural context of the unison call of the East African Crowned Crane Balearica regulorum gibbericeps. It speculates on the different functions of the unison call according to the situations where it is given. This is tested with the appeasement-threat hypothesis, which claims that the threatening acoustic characteristics of the unison call should be enhanced if it is given as a territorial call. In comparison, the appeasing acoustic characteristics should be stronger if the unison call is performed at flock sites where it possibly serves for mate assessment.     

The evolution of vocalisations in the genus Corvus: effects of phylogeny, morphology and habitat

In this study we investigated the phylogenetic, morphological and ecological factors affecting the caw calls of 28 species of the genus Corvus, spanning the worldwide range of the taxon. The three phylogeographic groups identified by Goodwin (1986, Crows of the World, British Museum (Natural History), St Edmudsbury Press, Bury St Edmunds), i.e. the American stock, the Palearctic-African stock and the Oriental-Australian stock, were differentiated by some of the acoustic features of their calls, suggesting that historical factors may have played an important role in the evolution of vocalisations in this group. To assess the effects of morphology (body size and bill length) and environment (open vs. closed habitat) and to simultaneously take into account the phylogenetic effects, we used the phylogenetically independent contrast method. This manner of analysis revealed that body size was important in shaping the acoustic attributes of the caw call, as it influenced two temporal and two spectral variables, whereas the effect of bill length was far weaker. Notably, our results did not confirm the negative correlation between call frequency and body size that resulted in a phylogeny-free analysis of the same data in many studies on passerines. Larger Corvus species, in fact, utter calls with higher fundamental frequency than those of smaller species. Hence, these results show that incorporating phylogeny in analyses can substantially alter the conclusions reached by studies carried out with non-phylogenetic approaches. The acoustic environment, considered one of the most important forces driving the evolution of vocalisations in passerines, slightly influenced only two acoustic parameters in the Corvusgenus, call fundamental frequency and duration of pulsed units, both of which increased in the calls of forest species.     

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.     

Solitary male chacma baboons in a desert canyon

Solitary and paired adult (nine) and subadult (one) male chacma baboons, Papio ursinus, were observed over a period of years living in part of a wooded desert canyon not used by adjacent troops. These extratroop males were silent when alone and gave only one alarm vocalization, the “wa-hoo” call, when paired. The space occupied by them is unsuitable for use by troops according to criteria for adequate sleeping sites and access to water. But the foods available to them, especially figs, but also other fruits and fresh acacia seeds, were abundant. These foods are more highly preferred by baboons than those foods available to troop members. Troop members deplete these resources and shift to less preferred foods with lower water content and longer processing times. All of the adult members of the troop adjacent to these isolated males were infected with a skin disease. Isolated males were not so afflicted and so cannot have originated from, or ever been a part of, this troop. They probably moved to the space where they were observed from other inland troops, traveling to their current home range along the narrow canyon river course.     

Vocalization of the tree frogPolypedates maculatus (Rhacophoridae)

The period of calling activity ofPolypedates maculatus lies between April and October. Males possess an indistinct subgular vocal sac which turns yellow during the breeding season. Mating calls type I, type II and distress calls have been identified. Mating calls type I and type II consist of a single pulse group. Type I call comprises of 7–22 pulses, whereas type II call consists of 4–6 pulses. Pulses are short. The frequency spectrum is broad and continuous. Distress calls, with 6 hormonics, are given by the females with their mouth open.     

Automated auditory detection of a rare,secretive marsh bird with infrequent and acoustically indistinct vocalizations

Autonomous recording units (ARUs) provide a non-invasive and efficient method for acoustic detection of elusive species across large temporal and spatial scales. However, species with indistinct vocalization structures can be a considerable challenge for automated signal recognizers. We investigated the performance of ARUs and signal recognizers in identifying the broadband, short-syllable, pulsed calls of a secretive, threatened marsh bird, the King Rail Rallus elegans. Other sympatric species in the same habitat also have repetitive calls within the same frequency range that can be difficult to distinguish. Following serial ARU deployments at specified sites in known breeding habitat, we conducted standardized callback surveys and nest searches to provide an independent measure of breeder density. To analyse recordings, we developed a signal recognizer based on user-input training files to detect two common call types, kek and grunt. Detections that remained following manual review of recognizer output revealed a previously undescribed seasonal decline and crepuscular diel pattern in calling rate. The rate of the grunt call also predicted density. These patterns emerged despite the recognizer's low precision and high false-positive rate, which were largely due to misclassification of other species' calls, although ambient noise and effective detection radius also limited the detectability of King Rail calls. We demonstrate that with informed ARU scheduling, improved ability to manipulate user-specified parameters within signal detection software, and attention to quality control, even the simplest call structures can be located consistently in a diverse acoustic landscape. Our behavioural findings will inform improvements to auditory surveys and to management of King Rails across their range.     

Habitual fission-fusion and social organization of the Hakone troop T of Japanese macaques in Kanagawa prefecture,Japan

To analyze the socioecological factors of habitual fission-fusion of troop members, which is an underreported phenomenon in Japanese macaques, the seasonal pattern of fission-fusion within the Hakone troop T in Kanagawa Prefecture, Japan, was examined. Although almost all the study troop members were included in a large-sized group in winter, a portion of its members of ten formed small subgroups from spring to autumn. The frequencies and age-sex composition of these subgroups changed seasonally. All troop members participated, more or less, in subgroup formation. Subgroups tended to be composed of animals of the same age-sex class. Troop members did not fission along matrilineal lines. Although the study troop members repeatedly joined with and parted from subgroups, the characteristic social structure of Japanese macaque troops was maintained. Habitual fission-fusion among troop members may be one of a number of foraging strategies that facilitate efficient food gathering when the population density exceeds and /or reaches the carrying capacity of the area. The seasonal variation of pattern and composition type of each subgroup could be attributed to alternation of attractive food plant species, as well as age, rank, and sexual activity of both sexes.     

Sources of Acoustic Variation in Rhesus Macaque (Macaca mulatta))Vocalizations

All species in the genus Macaca produce a set of harmonically rich vocalizations known as “coos”. Extensive acoustic variation occurs within this call type, a large proportion of which is thought to be associated with different social contexts such as mother-infant separation and the discovery of food. Prior studies of these calls have not taken into account the potential contributions of individual differences and changes in emotional or motivational state. To understand the function of a call and the perceptual salience of different acoustic features, however, it is important to determine the different sources of acoustic variation. I present data on the rhesus macaques' (M. mulatta) coo vocalization and attempt to establish some of the causes of acoustic variation. A large proportion of the variation observed was due to differences between individuals and to putative changes in arousal, not to differences in social context. Specifically, results from a discriminant-function analysis indicated that coo exemplars were accurately assigned to the appropriate individual, but vocal “signatures” were more variable in some contexts than in others. Moreover, vocal signatures may not always be reliable cues to caller identity because closely related individuals sound alike. Rhesus macaque coos evidently provide sufficient acoustic information for individual recognition and possibly kin recognition, but are unlikely to provide sufficient information about an external referent.     

Acoustic modulation of neural activity in the preoptic area and ventral hypothalamus of the green treefrog (Hyla cinerea)

Summary Responses of neurons in the preoptic area and ventral hypothalamus to conspecific mating calls or white noise bursts were examined in male green treefrogs (Hyla cinerea) during different seasons. In the winter, 34.3% of preoptic neurons and 46.7% of ventral hypothalamic cells demonstrated significant changes in activity level during presentation of a conspecific mating call. In contrast, only 13.3% of preoptic units and 16.7% of ventral hypothalamic cells responded to the white noise. The percentage of preoptic and hypothalamic units responding to the advertisement call did not differ significantly during the summer breeding season. Type I units exhibited a dramatic increase in activity during acoustic stimulation followed by a rapid return to baseline activity levels after stimulus offset. Type II cells showed a robust activity increase during stimulation, but maintained an intermediate activity level after stimulus offset. In the preoptic area, a third response type exhibited suppressed activity during acoustic stimulation. Although seasonal condition did not alter the percentage of acoustically responsive units within either nucleus, the proportion of Type I units in the ventral hypothalamus was greatest during the summer.Abbreviations MC mating call - NS no stimulus - POA preoptic area - VH ventral hypothalamus - WN white noise     

Divergence in calls but not songs in the orchard oriole complex: Icterus spurius and I. fuertesi

Birdsong has important functions in attracting and competing for mates, and song characteristics are thought to diverge rapidly during the process of speciation. In contrast, other avian vocalizations that may have non‐reproductive functions, such as calls, are thought to be more evolutionarily conserved and may diverge more slowly among taxa. This study examines differences in both male song and an acoustically simpler vocalization, the ‘jeet’ call, between two closely related taxa, Icterus spurius and I. fuertesi. A previous study comparing song syllable type sharing within and between I. spurius and I. fuertesi indicated that their songs do not differ discernibly. Here we measured 18 acoustic characteristics of their songs and found strong evidence supporting this prior finding. In contrast, we measured 17 acoustic characteristics of jeet calls and found evidence of significant divergence between the two taxa in many of these characteristics. Calls in I. fuertesi have a longer duration, a larger frequency bandwidth, a lower minimum frequency, a lower beginning frequency, and greater levels of both frequency and amplitude modulation in comparison to the calls of I. spurius. In addition, I. fuertesi calls contain two distinct parts, while the calls of I. spurius have only one part. Thus, we find evidence of divergence in the calls of the two taxa but not their songs challenging the widespread assumption that complex bird song evolves more rapidly than other types of vocalizations. Understanding divergence in multiple vocalization types as well as other behavioral, morphological, and molecular traits is important to understanding the earliest stages of speciation.     

Spatially-mediated call pattern recognition and the cocktail party problem in treefrog choruses: can call frequency differences help during signal overlap?

Male gray treefrogs, Hyla versicolor, advertise for mates in dense assemblages characterized by high levels of noise and acoustic clutter. In pairwise interactions, males alternate pulsatile advertisement calls and so reduce call overlap to levels below that expected by chance. However, in choruses consisting of more than two males, acoustic interference increases dramatically. Moreover, males do not seem to exhibit selective attention in a way that reduces call interference among nearest neighbours. Previous research has also demonstrated that although females discriminate strongly against overlapped calls, negative effects of call overlap can be attenuated by a large angular separation between signal sources. However, call stimuli employed were identical in spectrum and so this situation differs from that likely in nature. Based on studies of ‘auditory stream segregation’ with other taxa, we hypothesized that realistic differences in the frequencies of overlapping calls could improve the ability of females to discern critical call features during overlap of separated call sources. We found that, although, under some circumstances, differences in call frequency may help females distinguish among neighbouring males giving temporally proximate calls, naturalistic spectral differences do not seem to help females perceptually separate the overlapping calls of neighbouring conspecific males.     

The significance of call duration in howler monkeys

The “loud” calls of forest primates consist of repeated sounds that elicit a response from other members of the species. Recent studies suggest that these calls are often displays by the males that permit them to assess the strength of their opponents. Previous research on red howler monkeys supported the hypothesis that howling functions in assessment of competing individuals, as an alternative to energetically expensive chases and fights. As the second step in the attempt to understand the evolution of howling in genus Alouatta,one aspect—call duration — was compared in two species,the mantled howler (Alouatta palliata)and the red howler (A. seniculus).In A. palliatathe median howl duration was 3.5 sec and the interhowl interval was 20.0 sec, while in A. seniculusthe median howl duration was 19.0 sec and the interhowl interval was 3.0 sec. During the dawn chorus, the total duration of calling in A. seniculusmay be 10 or more times greater than that in A. palliata.The latter species appears to be limited in the duration of howls it can produce, so it increases the amount of calling by reducing the interhowl interval. At least four factors may be important in the evolution of the observed differences in call structure: constraints of the acoustic environment, alternate forms of display used by A. palliata,the presence or absence of competing males within the troop, and the effect of female calls on male howling. The observations suggest that the use of the male loud call may reflect differences in the nature of male-male competition and female support more than it reflects the constraints of the acoustic environment.     

Advertisement calls of two anuran amphibians,Rana tigrina andTomopterna breviceps

Rana tigrina andTomopterna breviceps occur as sympatric species at Dharwad, India. Sexually mature males produce advertisement calls. The advertisement call of both the species consist of a number of calls produced in series forming a call group. Each call group ofRana tigrina comprises 10–40 calls, whereas that ofTomopterna breviceps consists 13–141 calls. Each call consists of a pulse group with variable number of pulses which lack pulse interval. Calls of both the species exhibit similarities in (i) call consisting of series of calls with a pulse group in each call, (ii) absence of pulse interval within the pulse group, (iii) the amplitude of the first pulse being always small, and (iv) the frequency spectrum beginning from 200 Hz. Based on the similarities in the spectral features of the calls, it is suggested that the two species may be closely related to each other.     

Vocal coordination of troop movement among white-faced capuchin monkeys,Cebus capucinus

Coordinated travel by social groups is well documented, often with evidence that cognitive spatial maps are employed. Yet the mechanisms by which movement decisions are made and implemented within social groups are poorly known. In a field study of white-faced capuchin monkeys in Costa Rica it was demonstrated that a specific call, the “trill,” is used by adults in the initiation and directing of troop movement. The trills of subadults were restricted to vocal exchanges with other subadults. Continuous vocal recordings were collected of the vocalizations of the 14 members of the study troop. A cumulative 33.7 h of continuous samples and 1,892 sonagrams were analyzed. In addition to vocalizations clearly associated with alarm, distress, or agonistic contexts, two distinct call types were identified, trills and huhs. Age-sex classes differed in the rate at which both types of calls were produced in different spatial positions within the troop. Adult females and males produced higher rates of trills when in the leading edge compared to all other spatial positions in a traveling troop. Trills at the edge of a stationary troop represented 36 “successful” and 3 “unsuccessful” start attempts; the troop usually moved in the trajectory predicted by a trilling adult's location on the troop periphery within 10 min of the initiation of trilling. Adults also altered the trajectory of traveling troops by trilling at the side and back of the troop (10 “successful” and 4 “unsuccessful” attempts). Huh vocalizations were most predictably produced when a capuchin is in a dense fruit patch. These results emphasize the role vocalizations serve in the coordination and trajectory of group movement in nonhuman primates, especially those populations that are arboreal or in which visual contact is otherwise impeded. © 1993 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

The function of loud calls (Hoot Series) in wild western gorillas (Gorilla gorilla)

The use of loud vocal signals to reduce distance among separated social partners is well documented in many species; however, the underlying mechanisms by which the reduction of spacing occurs and how they differ across species remain unclear. Western gorillas (Gorilla gorilla) offer an opportunity to investigate these issues because their vocal repertoire includes a loud, long‐distance call (i.e., hoot series) that is potentially used in within‐group communication, whereas mountain gorillas use an identical call exclusively during intergroup encounters. First, we tested whether the hoot series functions as a contact/separation call. Second, we examined which individuals were more likely to reply and which party was more responsible for decreasing distance to identify the underlying mechanisms and cognitive implications of hoot series. We collected behavioral, spatial, and acoustic data on five adult gorillas over 15 months at the Mondika Research Center (Republic of Congo and CAR). Hoot series are individually distinct calls and given by both male and female gorillas when separated from each other. Following hooting, the distance between separated group members decreased significantly; thus we concluded that western gorillas use this call to reestablish group cohesion. The way in which proximity was achieved depended upon listeners replying or not to the caller. Replies may indicate a conflict between callers about intended travel direction, with vocal interchanges serving to negotiate a consensus. Although the acoustic features of vocal signals are highly constrained in closely related species, our results demonstrate that the function and usage of particular calls can be flexible. Am J Phys Anthropol 155:379–391, 2014. © 2014 Wiley Periodicals, Inc.