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Vocal Repertoire of White-faced Sakis (Pithecia pithecia)
... For P. pithecia, data from Henline's (2007) study conducted in Isla Redonda, Venezuela (7.766, -62.883) was used, and P. aequatorialis data came from Keiren's (2012) study in the Tahuayo River Amazon Research Center, Peru (-4.383, -73.25). While Henline's (2007) study was conducted before the reclassification of Pithecia species, it is clear that this study did not include vocalisation from P. chrysocephala as the in-situ part of the study was conducted in Venezuela, far from the natural range of this species, but within that P. pithecia. Our study and the two previous studies each report between 5 and 12 distinct vocalisations per species (Table 1). ...
... Table 1. The complete adult vocal repertoires of P. chrysocephala, P. pithecia, and P. aequatorialis as recorded by Muir et al. (2019), Henline (2007), and Keiran (2012). P. aequatorialis calls were not put into groups within their study and so have been grouped according to their similarity to the others based on their description and/or behavioural context. ...
... At a glance, structural properties between Pithecia pithecia calls in Henline (2007) and those of the current study of P. chrysocephala are very similar, with chucks being the shortest calls, throat rattles the longest, chucks and trills at the highest frequencies, and soft growls at the lowest. However, few calls between these species were sufficiently similar on spectrograms to be compared statistically. ...
Information on primate vocalisations can be applied in several ways, including: improving captive welfare, as a census tool for cryptic species, or to investigate the impacts of anthropogenic disturbance on species’ behaviour (Delgado and van Shaik, 2000; Konrad and Geissman, 2006; Jacobsen et al., 2010). Vocalisations can be used as a taxonomic tool, and structural differences between calls have been used to compare a wide variety of taxa, including species of gibbon (Hylobatidae spp., Ruppell, 2010), marmosets (Callithrix spp., Mendes et al., 2009), owls (Strigidae spp., Flint et al., 2015), wolves (Canis spp., Kershenbaum et al., 2016), and galagos (Galagidae spp., Svensson et al., 2017). Additionally, differences in voca- lisations across taxonomic groups can be used to help determine genetic distances between species or investigate why vocal behaviours evolved (Blumstein and Armitage, 1998; Ord and Garcia-Porta, 2012).
... The recent revision of the taxonomy of the genus Pithecia describes 16 full species where there were previously 5, creating a need for further research on these species, including their vocalizations Marsh 2014). Previous studies of vocal behavior in Pithecia have described 7-18 call types in Pithecia pithecia and Pithecia aequatorialis (Buchanan 1978;Henline 2007;Keiran 2012). ...
... Our goals were to determine the vocal repertoire of Pithecia chrysocephala, investigate the behavioral contexts in which they use calls, and examine the association between behavioral context and call structure. We tested predictions derived from five hypotheses: 1) If congeneric species have similar vocal repertoires (see Henline 2007 for Pithecia), then the vocal repertoire of P. chrysocephala will consist of 7-18 calls. 2) If the P. chrysocephala vocal repertoire fits the Social Complexity Hypothesis (Freeberg et al. 2012), then vocal repertoire size will be comparable to that of other New World species with similar group sizes and family structure, such as Aotus spp. ...
... We grouped calls according to their structural differences in spectrograms, their duration, frequency of maximum energy, lowest frequency, start frequency, end frequency, and by ear. When naming calls, we used Henline's (2007) categories for Pithecia pithecia calls where appropriate; otherwise we chose new names onomatopoetically. We used a cross-validated discriminant function analysis (DFA) to assess the reliability of the recorded vocal repertoires. ...
Vocalizations are a vital form of communication. Call structure and use may change depending on emotional arousal, behavioral context, sex, or social complexity. Pithecia chrysocephala (golden-faced sakis) are a little-studied Neotropical species. We aimed to determine the vocal repertoire of P. chrysocephala and the influence of context on call structure. We collected data June–August 2018 in an urban secondary forest fragment in Manaus, Amazonian Brazil. We took continuous vocal recordings in 10-min blocks with 5-min breaks during daily follows of two groups. We recorded scan samples of group behavior at the start and end of blocks and used ad libitum behavioral recording during blocks. We collected 70 h of data and analyzed 1500 calls. Lowest frequencies ranged 690.1–5879 Hz in adults/subadults and 5393.6–9497.8Hz in the only juvenile sampled. We identified eight calls, three of which were juvenile specific. We found that, while repertoire size was similar to that of other New World monkeys of similar group size and structure, it also resembled those with larger group sizes and different social structures. The durations of Chuck calls were shorter for feeding contexts compared to hostile, but frequencies were higher than predicted if call structure reflects motivation. This finding may be due to the higher arousal involved in hostile situations, or because P. chrysocephala use Chuck calls in appeasement, similar to behavior seen in other primates. Call structures did not differ between sexes, potentially linked to the limited size dimorphism in this species. Our findings provide a foundation for further investigation of Pithecia vocal behavior and phylogeny, as well as applications for both captive welfare (stress relief) and field research (playbacks for surveys).
... Saki species have, at least, three loud calls that could possibly be related to group coordination and defence of resources (Henline 2007). Uacari species have context and agespecific calls as well as calls uttered in a range of different behavioural contexts (Fontaine 1981; Bezerra et al. 2010a. ...
... By comparing the similarities of the vocal repertoires of captive populations with those used by wild conspecifics, zookeepers and laboratory managers could provide the necessary stimuli to expand the vocal repertoire (and perhaps enrich the environment) of captive animals. This could be made possible for Cacajao ouakary (Bezerra et al. 2010a), Pithecia irrorata (Adams and Erhart 2009), Pithecia pithecia (Henline 2007), and some titi monkeys (Electronic Supplementary Material 1). The study and description of vocal repertoires of wild pitheciids for this purpose should be encouraged. ...
The variation in ecological traits in pitheciids allow investigation of vocal communication across a range of social and acoustic circumstances. In this review, we present a summary of the history of pitheciid vocal studies, and review i) the status of current knowledge of pitheciid vocal repertoire sizes, ii) how much we understand about the context of different acoustic signals, and iii) how can we potentially use our knowledge of vocalizations in animal welfare practices. The repertoires described for titi monkeys and sakis have the expected sizes for these genera, considering their relatively small social group sizes. However, uacari groups can contain over 100 individuals, and a larger vocal repertoire than the ones described would be expected, which could be a consequence of the fissionfusion social system where the large group divides into smaller subgroups. Nevertheless, vocal repertoires exist for only about 12% of the pitheciid species and nothing is known, for example, concerning call ontogeny. We hope that this study will act as a reference point for researchers interested in investigating vocal behaviour in pitheciids, thus, optimising both funding focus and, researcher's time and effort. Also, we hope to help defining methodologies and strategies for the conservation and management of pitheciid monkeys.
... There is no definitive data upon sakis' hearing capabilities, but Henline [55] found their vocal range to span about 900 to 7000 Hz in fundamental frequencies, with some formant frequencies reaching up to 17,000 Hz. Out of these, the higher frequency whistles were typically related to solo activities, such as feeding or object manipulation, when around other individuals. ...
Simple Summary
Animals living in captivity can benefit from new forms of technological enrichment, with auditory enrichment currently being underutilized. Here, we investigate how to provide zoo-housed white-faced saki monkeys with auditory enrichment in an animal-centred manner. To study this, we prototyped and developed an interactive system that the sakis could trigger to play audio and that tracked their interactions with the device. Importantly, we incorporated this system into the regular living environment of the sakis and developed the interaction in a way that gave them control over activating the sounds. Based on the results, we conclude that audio is a promising way to provide enrichment for small primates like sakis. Utilising our device, we demonstrate that the sakis triggered the traffic audio more than silence, rain, zen, and electronic music, with no differences between the other conditions. However, we highlight problems in using this behaviour to infer the sakis preference or how they like the system, with further research needed towards sounds for audio enrichment. Our method reveals the value of collecting early real-world data and prototyping when designing interactive technologies for zoo-housed animals. In this experiment, we found that animal-centred methods can help create technologies better suited to their purpose and ultimately towards the end-goal of improving animal welfare.
Abstract
Computer systems for primates to listen to audio have been researched for a long time. However, there is a lack of investigations into what kind of sounds primates would prefer to listen to, how to quantify their preference, and how audio systems and methods can be designed in an animal-focused manner. One pressing question is, if given the choice to control an audio system, would or could primates use such a system. In this study, we design an audio enrichment prototype and method for white-faced sakis that allows them to listen to different sounds in their regular zoo habitat while automatically logging their interactions. Focusing on animal-centred design, this prototype was built from low fidelity testing of different forms within the sakis’ enclosure and gathering requirements from those who care for and view the animal. This process of designing in a participatory manner with the sakis resulted in an interactive system that was shown to be viable, non-invasive, highly interactive, and easy to use in a zoo habitat. Recordings of the sakis’ interactions demonstrated that the sakis triggered traffic audio more than silence, rain sounds, zen, and electronic music. The data and method also highlight the benefit of a longitudinal study within the animals’ own environment to mitigate against the novelty effect and the day-to-day varying rhythm of the animals and the zoo environment. This study builds on animal-centred methods and design paradigms to allow the monitoring of the animals’ behaviours in zoo environments, demonstrating that useful data can be yielded from primate-controlled devices. For the Animal-Computer Interaction community, this is the first audio enrichment system used in zoo contexts within the animals own environment over a long period of time that gives the primate control over their interactions and records this automatically.
... Los tchó parecen tener un papel importante en la coordinación de las actividades del grupo y pueden contener pistas acerca de la identidad del remitente y del contexto asociado de comportamiento . Excepto por un estudio no publicado sobre el repertorio vocal de Pithecia pithecia (Henline 2007), los Pithecia y Chiropotes raramente han sido objeto de estudios sobre la comunicación acústica. Los pocos datos disponibles para estos géneros corresponden a informes sobre el contexto y la frecuencia de uso de algunos tipos de vocalizaciones contenidos dentro de estudios con otros enfoques (Di Fiore et al. 2007;Suleima & Ferrari 2009). ...
... Los tchó parecen tener un papel importante en la coordinación de las actividades del grupo y pueden contener pistas acerca de la identidad del remitente y del contexto asociado de comportamiento (Bezerra et al. 2010a). Excepto por un estudio no publicado sobre el repertorio vocal de Pithecia pithecia (Henline 2007), los Pithecia y Chiropotes raramente han sido objeto de estudios sobre la comunicación acústica. Los pocos datos disponibles para estos géneros corresponden a informes sobre el contexto y la frecuencia de uso de algunos tipos de vocalizaciones contenidos dentro de estudios con otros enfoques (Di Fiore et al. 2007;Suleima & Ferrari 2009). ...
... White-faced sakis (Pithecia pithecia) are lower-strata dwellers that have a vocal repertoire of between 12-18 distinct calls, including an "alarm chuck" (Henline, 2007;Buchanan et al., 1981). Henline also reports several vocalizations as being utilized in the context of "heterospecific" interactions, and although Buchanan and colleagues (1981) report an "alarm chuck" vocalization, these vocalizations appear to be used in more contexts than the specific alarm vocalizations emitted by other neotropical species. ...
I studied the vocalizations of wild saki monkeys (Pithecia spp.) in the Área de Conservacíon Regional Comunal de Tamshiyacu-Tahuayo (ACRCTT), Peru. Sakis are little studied in the wild and occupy dense, seasonally flooded, lowland rainforest, which makes extended visual contact with them difficult. Their vocalizations can be used to find groups, localize and track individuals, identify group activities when visibility is poor, and to help identify species. Vocalizations were recorded ad libitum as MP3 files using a parabolic stereo microphone attached to a digital linear recorder, then analyzed using Raven Pro 1.3 bioacoustic software. Behavioral data on individuals and groups and habitat information was noted when possible. I identified 11 main call types with at least 4 call variations, verified using the Kruskal-Wallis test followed by Dunn’s Multiple Comparisons post hoc test (Zar 1984) on call attributes of the minimum and maximum frequency, frequency range, and duration. I compared these calls with spectrographs of calls of P. pithecia (Buchanan 1978, Henline 2007), P. monachus (Buchanan 1978) and P. aequatorialis (Sounds of Neotropical Rainforest Mammals, Cornell Laboratory of Ornithology) from published sources. Using the calls of the species that aurally and visually resembled the unidentified Pithecia sp. an ANOVA was performed comparing P. aequatorialis calls with Pithecia calls from the ACRCTT, identifying the species in the reserve as potentially being P. aequatorialis. Based on geographic range, physical descriptions and vocalization analysis, I concluded that P. aequatorialis is the most likely candidate for the previously unidentified saki species in the ACRCTT. Pithecia aequatorialis has not been previously been reported south of the Amazon River and its vocalizations have not been described previously. With the genus Pithecia undergoing review, vocalizations may provide an important aid in species identification.
Female baboons,Papio cynocephalus ursinus, often grunt when approaching lower-ranking females. These grunts appear to have a mollifying effect on subordinates. Observations of 19 adult females conducted over an 11-month period in the Okavango Delta, Botswana, revealed that high-ranking females were less likely to supplant more subordinate females, and more likely to engage in friendly interactions with them, when they grunted to their lower-ranking partners than when they remained silent. Grunts also functioned to reconcile opponents following fights. In a series of playback experiments, subjects were played the potentially threatening scream of a higher-ranking female that had recently attacked them. Subjects responded less strongly to these screams when the dominant opponent had apparently reconciled after the fight by grunting to them than when the opponent had not interacted with them again. Subjects' responses after a vocal ‘reconciliation’ were similar to their responses following a control period when the two females had not interacted at all. Even in the absence of more overt friendly behaviour, therefore, baboon grunts act to restore the relationship of opponents to baseline tolerance levels.
Capuchin monkeys, Cebus olivaceus, combine different types of calls to form compound calls. These compound calls are syntactically organized (i. e. , there is a predictable ordering of call types in the compound call). The analysis of the syntax of animal communication necessarily includes: (a) Accurate classification of types of calls, and a demonstration that calls that occur both alone and in compound calls are structurally similar. (b) Description of the syntactic rules generating compound calls or call sequences, and classification of types of compound calls or call sequences. (c) Examination of the social circumstances or contexts in which both single and compound calls occur. I followed these steps using a large sample of Cebus olivaceus calls, recorded in riparian gallery forest in central Venezuela. The calls were initially screened using a real-time spectrum analyzer, and a group of structurally related call types was selected for further analysis. Temporal and frequency characteristics of 868 of these calls were measured from sound spectrograms produced on a sound sonograph. Call classification involved first defining a very large number of possible call types on the basis of these characteristics, and then using a discriminant analysis to identify which types should be lumped together. A stepwise procedure was followed, using only calls which occurred singly, until five call types (squaws, chirps, trills, whistles, screams) were statistically separable. Two of these types (trills, whistles) showed considerable within-type variation and were further subdivided into four variants each. Discriminant analysis was then used to demonstrate structurally similarity between calls produced singly and those in compound calls. Social circumstances were defined using similarities in the vocalizer's actions, arousal, orientation to and distance from the presumed receiver. Use of call types, when given singly, covaried predictably with social circumstances and presumably with the internal state of the vocalizer. Different calls expressed different internal states on a continuum from contact-seeking to contact-avoiding. Use of trill and whitle variants also covaried with social circumstances. Different variants expressed different states on a continuum from affiliation or submission to aggression. Combinations of internal states, in theory, might be expressed as intergradations or intermediates between different call types. However, such intermediate states are often coded syntactically. Syntactically organized compound calls accounted for 38% of the total sample. The distribution of social circumstances in which compound calls are given was intermediate between the distributions of the constituent call types, which presumably indicates an intermediate internal state. Compound calls are generated by syntactic rules closely analogous to lexical rules of human language. Specifically they act like compounding rules that combine two lexical entries to form a third. They are not analogous to the grammatical rules that generate human sentences.
The social behaviour of many species of non-human primates suggests a capacity for both individual and kin recognition. In these species, the ability to signal and perceive identity at a distance may be an important adaptation facilitating intra-group social communication. Variation in vocalizations is hypothesized to provide a basis for this ability. Playback experiments were conducted to test for vocal recognition of contact calls between adult female rhesus macaques,Macaca mulatta. Single-trial playbacks of the contact call of either a matrilineal relative or a familiar, non-relative group member were used to test for discrimination of kin from non-kin. Females responded significantly faster and longer to the contact calls of matrilineal relatives. A habituation–discrimination paradigm was then used to test for individual recognition. Females habituated to successive presentations of different exemplars of the contact calls of one matrilineal relative, then showed a significant rebound in response to the subsequent presentation of a contact call from a second matrilineal relative. These results indicate an ability for vocal recognition of both individuals and kin. Females' responses to playbacks suggested the additional possibility for categorical recognition of matrilineal kinship, or its correlates.
Pithecia pithecia andChiropotes satanas are seed predators that eat fruits with hard pericarps. We measured resistance to puncturing and crushing of fruit and seeds eaten by these two pitheciins at two localities: in evergreen rain forest at Raleighvallen-Voltzberg, Surinam, and in tropical dry/transitional moist forest on islands in Guri Lake, Venezuela. Average measurements of pericarp hardness were similar at both sites for fruit eaten byChiropotes, but a higher maximum value was obtained at the rainforest site.Chiropotes andPithecia both ate fruits that had harder pericarps than did fruits eaten byAteles paniscus, but crushing resistances of seeds eaten were lower than values forAteles. Thus, both pitheciins selected fruits with hard pericarps and soft seeds, although there were notable intergeneric differences in hardness of fruit ingested. When fruit became scarce,Pithecia ate more flowers, whileChiropotes continued to eat fruits with hard seed coverings. Chemical analysis of species of seeds eaten byPithecia suggests that they avoided seeds with extremely high tannin levels, though they tolerated moderate tannin levels in combination with high levels of lipids. We propose that sclerocarpic harvesting (the preparation and ingestion of fruit with a hard pericarp) allows pitheciin monkeys to obtain nutritious seeds, with reduced tannins, that are softer than those ingested by other frugivores.
White-faced sakis (Pithecia pithecia) are Neotropical seed predators that ingest a mixed diet of fruit, leaves, and insects. We report timed feeding data for a 12-mo period on a group of 8 white-faced sakis occupying an island—a portion of their original home range—in Lago Guri, Venezuela. We collected fruit and leaf samples, dried them in the field, and analyzed them to measure nutrient content—free simple sugars (FSS), crude protein (CP), lipids, and total nonstructural carbohydrates (TNC)—and the presence of antifeedants: total tannins, condensed tannins and dietary fiber. We weighted nutrients and antifeedants by timed feeding samples to estimate actual intake. Then we compared intake among months and seasons. Compared with other frugivores, the average monthly intake of lipids was extremely high (16.1% by dry matter estimate(DM)), attributed to ingestion of young seeds and other plant parts that were relatively high in lipids, e.g., seed arils. Intake of FSS and CP were relatively low: 3.4% DM and 6.5% DM, respectively. The average intake of total cell wall or neutral detergent fiber (NDF = 38.4% DM) was only slightly lower than the range reported for colobines. Average intake of tannins was within the range reported for cercopithecines: condensed tannins of 3.3% Quebracho units standard (QU). We suggest that white-faced sakis accept a trade-off for food items that are fibrous or astringent if they are also rich in lipids. White-faced sakis expand the typical definition of primate fruit-eater in their high lipid-relatively high NDF-low FSS diet.
The daily movements and the resulting activity and calling fields are described for three groups of titi monkeys Callicebus moloch. Groups move to the periphery of their home range in the early morning and then call. Playback experiments confirmed that both proximity and location of calling by neighboring animals affect the group's response. Subsequent countercalling often regulates the approach of neighboring groups to a boundary. After encountering adjacent groups, animals return to areas near the home range center. Movements, calling behavior, and the response to neighboring groups all increase the probability of intergroup encounters in the early morning. Encounters define and reinforce the conventional location of boundaries. Boundaries decrease the probability of intergroup encounters at other times and allow exclusive use of space.
To advance knowledge of the vocal communication associated with close proximity social interactions in Garnett's greater bush baby (Otolemur garnettii), we measured acoustic and temporal properties of vocalizations from videotaped recordings of captives in two main social contexts: mother-infant interactions and adult male-female pair introductions and reintroductions. We used a real-time sonagraph or software program to display, edit, and analyze vocal waveforms, and to provide wideband and narrowband spectrograms. Vocalization characteristics measured include fundamental frequency (via inspection of harmonics) and spectral features such as formant frequency, intensity, and duration. The vocal repertoire contained 4 major types of vocalizations: 1) barks and complex multiple bark sequences, 2) low frequency flutter/hums and growls, 3) high frequency clicks and spits, and 4) noisy shrieks. We describe several vocalizations for the first time and provide a clear classification of some of them on the basis of call durations (long/short growls). Complex bark sequences, previously described as distant communication calls, were invariant and were not often emitted by individuals when in close proximity. When classified spectrographically, the remaining 3 call types, which occurred when individuals were in close proximity, were less stereotypical, and gradations within call types were apparent. Our results show that although nocturnal and non-gregarious, complex communicatory signals of bush babies constitute a vocal repertoire formerly thought to be characteristic only of diurnal, gregarious primates.
White-faced sakis (Pithecia pithecia) are well known for their specialized feeding strategy and dependence on seed-eating, but we know less about social dynamics and reproduction. I summarize data from 1990 to 2001 on sakis inhabiting a small island in Lago Guri, Venezuela that includes changes in group composition, aggressive behavior, and female reproductive histories. Though the characteristic group size and typical mating system are still uncertain for wild, free-ranging Pithecia spp., size of the study group ranged from 2–3 adult females and 1–4 adult males. My group and I collected fecal samples from adult females, which we dried and assayed for estrogen (E1C) and progesterone (PdG) conjugates to document reproductive cycles and female development. During the study, as many as 3 females were either cycling or pregnant at the same time. Ten infants were born during the study, 4 of which survived to adulthood. Five interbirth intervals after weaning an infant ranged from 12 to 36mo. Though researchers often assume Pithecia spp. are monogamous, multiple breeding females can coexist in groups without evidence of reproductive suppression. Within the pitheciine clade, Pithecia spp. exhibit a mosaic of behavioral and morphological traits intermediate between bearded sakis and uakaris on the one hand and their sister-group, the pair-bonded titis, on the other.
Monogamous primates maintain exclusive use of their ranges by regularly defining and reinforcing the conventional location
of boundaries.Callicebus moloch males often call alone during the first morning bout, when groups are near boundaries but usually separated by more than
100m. Depending on the location and proximity of neighboring animals, groups might begin duetting and approaching one another.
Duetting requires close vocal and spatial coordination of the mated pair, and stimulates the approach of neighboring pairs.
At the boundary, vocalizations which keep the pair together and those associated with withdrawal from the boundary increase
in proportion. To determine the effect of different calls, I played back recordings of six different vocalizations during
two playback experiments, holding location and proximity constant. The responses supported hypotheses generated in the normalistic
study, and suggested that at the boundary aggression is primarily intrasexual. Vocalizations and their effects in specified
contexts constitute the mechanisms regulating spacing. The resulting spacing patterns maintain resource availability and exclusive
access to a mate.
Primate long-distance calls have typically been interpreted as communication signals between conspecific groups (the ‘resource defence hypothesis’), but their potential role as anti-predator alarm calls has received comparably little attention. Male diana monkeys,Cercopithecus diana dianain the Taı̈ forest of Côte d’Ivoire often utter long-distance calls, either spontaneously or in reaction to a variety of stimuli, including predators and non-predators. The present study focuses only on predation contexts and provides evidence for communication to both predators and conspecifics. Males called only in response to predators whose hunting success depends on unprepared prey, that is, leopards and crowned hawk eagles, but not in response to pursuit hunters, such as chimpanzees and humans, which can pursue the caller in the canopy. Calling was regularly combined with approaching the predator. Both observations suggest that male long-distance calls are used to signal detection to the predator (‘perception advertisement hypothesis’). Analysis of male long-distance calls given to leopards and eagles showed that they differed according to a number of acoustic parameters. The two call variants were played to different diana monkey groups; conspecifics responded to them as though the original predator were present. We conclude that, in addition to their function in perception advertisement, diana monkey long-distance calls function as within-group semantic signals that denote different types of predators.
From a plant's perspective, the difference between a seed predator and a seed disperser should be straightforward: attract animals that will disperse seeds and defend seeds from potential predators. Unlike pulp-eating frugivores, seed predators regularly encounter diverse plant protective mechanisms. The purpose of this paper is to examine feeding constraints, morphological adaptations, and the mechanical process of seed predation. While there is evidence that some seed predators cause severe losses to seed crops, there is also evidence that seed predators enhance seed dispersal and germination. We also examine four methods by which neotropical seed predators may contribute to dispersal. 1) Seed predators examined here ingested fruit when seeds were full-sized, but not yet mature (i.e., seeds of mature fruit may be avoided by seed predators and available for dispersal by other frugivores). 2) Sympatric seed predators may ingest seeds from different plants thus reducing overall predator load on any individual plant. 3) Seed predators that manipulate seeds (e.g., remove pericarp and seed coat) may enhance germination if the prepared seeds are dropped, discarded, or buried and not ingested. 4) Small seeds may miss mastication and swallowed intact with a food bolus. The last mechanism is the most likely to contribute to seed dispersal by the widest array of vertebrate seed predators, but primate seed predators may facilitate seed dispersal using all four mechanisms. Therefore, the traditional dichotomy of seed predator vs. seed disperser oversimplifies the interactions between seed predators and plants.
This study has addressed the acoustical structure of male loud calls and their function in Thomas langur social organisation. Thomas langurs are medium sized primate that lives in Sumatra, Indonesia. Ome of the characteristics of this species is the loud call of males. Several functions for loud calls have been suggested such as mate-defence, resource-defence and mate-attraction. In this study playback studies were applied to determine that loud calls function in between-group spacing and resource-defence. The function of loud calls in mate-attraction was not demonstrated directly, but an analysis of long-term data showed that females often choose newly adult males when the transfer between groups. These newly adult males have loud calls of shorter duration than adult males that already have associated with females and have offspring. This indicates that females may use loud calls as a cue to choose newly adult males. Since newly adult males are better in protecting offspring against infanticidal extra-group males and predators, it is functional for females to choose these males. In addition, it was shown that males show individual variation in loud call characteristics and that calls also differ between behavioural context, such as dawn chorus or alarm.
White-faced sakis (Pithecia pithecia) are among the least studied neotropical primates. The combination of shy and quiet behavior, their ability to move silently, and the extreme difficulty of capturing them may explain why very few field studies have been undertaken in undisturbed habitats. During the course of a wildlife rescue in French Guiana, six individuals were captured and translocated to a safe area of primary rainforest. In this area, based on the observation of 35 groups, the average group size was 2.3 animals (SD = 1.2) and a density of 0.28 group/km(2) (0.64 individuals/km(2)) was estimated from transect censuses. Our study focused successively on three radio-collared animals (two males and one female) over a 287-day period, starting from release to the loss of the animal. From the study start, the triangulation method was used prior to habitutation to human presence, followed thereafter by 1,327 hr of visual monitoring. The translocated animals settled down, and two of them had a stable and compact home range. Two of them merged in association with members of the resident population. A resident group had a much larger home range than previously reported: 148 and 287 ha, using grid cells and 100% minimum convex polygon techniques, respectively. A group composed of two translocated individuals (one male and one female) had a home range of 68 and 135 ha using the same techniques. Additionally, two solitary animals used 152 and 162 1-ha quadrats. We observed animals (translocated and residents) moving quickly in one direction up to 11.5 km. The mean daily path length of resident animals was 1,880 m. Sakis used the lower strata of the forest more when in group, and the intermediate strata more when solitary. Allogrooming is fairly common in social groups. On average, the activity period ranged from 7:17 to 15:59 hr.
This book will be a landmark text for all those interested in animal communication. Animal Vocal Communication explicitly avoids human-centred concepts and approaches and links communication to fundamental biological processes instead. It offers a conceptual framework - assessment/management - that allows us to integrate detailed studies of communication with an understanding of evolutionary perspectives. Self-interested assessment is placed on par with the signal production (management) side of communication, and communication is viewed as reflecting regulatory processes. Signals are used to manage the behaviour of others by exploiting their active assessment. The authors contend that it is this interplay between management and assessment that results in the functioning and evolution of animal communication; it is what communicative behaviour accomplishes that is important, not what information is conveyed.
Female baboons, Papio cynocephalus ursinus, often grunt when approaching lower-ranking females. These grunts appear to have a mollifying effect on subordinates. Observations of 19 adult females conducted over an 11-month period in the Okavango Delta, Botswana, revealed that high-ranking females were less likely to supplant more subordinate females, and more likely to engage in friendly interactions with them, when they grunted to their lower-ranking partners than when they remained silent. Grunts also functioned to reconcile opponents following fights. In a series of playback experiments, subjects were played the potentially threatening scream of a higher-ranking female that had recently attacked them. Subjects responded less strongly to these screams when the dominant opponent had apparently reconciled after the fight by grunting to them than when the opponent had not interacted with them again. Subjects' responses after a vocal 'reconciliation' were similar to their responses following a control period when the two females had not interacted at all. Even in the absence of more overt friendly behaviour, therefore, baboon grunts act to restore the relationship of opponents to baseline tolerance levels.
Three factors, environment, quality and type of interaction, and phylogeny have been hypothesized to influence the structure of signal repertoires in primates. Much is known about vocal repertoires of terrestrial, savannah-dwelling species and arboreal, rainforest-dwelling species, but very little is known about terrestrial rainforest species. To fill this knowledge gap and to further elucidate how the three factors influence vocal repertoires of primates, we designed a study on sooty mangabeys (Cercocebus torquatus atys), a terrestrial Old World primate that lives in dense rainforests. Recordings of sooty mangabeys in their natural environment were used to compile the vocal repertoire of this species. All calls are described according to the basic acoustical structure and the behavioral context in which they occurred. Descriptions are supplemented by quantitative measurements of call occurrence in all age–sex classes. For the most frequently produced vocalizations, a preliminary acoustical analysis was conducted to test for individual and contextual differences. Finally, we compare vocalizations of sooty mangabeys with vocalizations of several other primate species and discuss how the factors mentioned above might influence the vocal repertoire of sooty mangabeys.
The ability to recognize a conspecific signal is essential to communication. In addition to recognizing the type of call, receivers extract a range of information from the signal about the producer, including identity, sex and dialect. Despite the apparent ease with which this is accomplished, few available data address the computational processes underlying recognition. While it is possible that recognition of the signal and its information content occur in a single stage of processing, different components of the signal may be processed separately. Here we present a series of experiments designed to examine this issue in the cottontop tamarin, Saguinus oedipus. Using the tamarins' natural vocal response to hearing their species- specific combination long call (CLC), antiphonal calling, we presented tamarins with manipulated and unmanipulated CLCs and measured both the number of antiphonal responses and the latency to produce an antiphonal call. Results indicated that recognition of the call type and recognition of the caller occur in separate computational stages of signal processing. These data provide insights into how sensory information is organized by a call recognition system.
It had been shown that Barbary macaque (Macaca sylvanus) mothers are able to individually recognise their offspring by its vocal signals, but it remained unclear which acoustical cues may account for such an ability. In order to address this issue from a basic perspective, about 1800 calls of infants and yearlings (N = 10) were investigated. The investigation applied a method of signal analysis which allowed to determine a large number of parameters (N = 84) for each vocal signal. The application of discriminant and cluster analyses provided the following results: (1) Animals differed in almost all call parameters. However, individuals were best identified by specific parameters which formed an individually characteristic parameter set. (2) Those parameters that facilitated the assignment of vocal patterns to a given individual usually were different among individuals. (3) Infants and yearlings achieved the same maximum value of correct assignment. However, infants achieved a reasonable assignment at a much small er number of call parameters. (4) Cluster analysis of vocalisations revealed that Barbary macaques uttered individual versions of common call types. (5) When the discriminant analysis was rerun on the call clusters, the correct assignment could be improved from 81% to 94% for infants and from 80.5% to 96% for yearlings. Our findings suggest that Barbary macaque mothers can recognise their offspring by more than one signal cue, and such a strategy may improve the recognition system's robustness against possible distortions caused by the environment. The pronounced differences in vocal patterns of young Barbary macaques may help mothers or other group members to readily learn and recognise the individually specific signal features. The methodological procedures described in this paper provide a powerful tool for an assessment of signal parameters also in other areas of vocal interactions.
This study describes selection derived from habitat acoustics on the physical structure of avian sounds. Sound propagation tests were made in forest, edge, and grassland habitats in Panama to quantify pure tone and random noise band sound transmission levels. The sounds of bird species in each habitat were analyzed to determine the emphasized frequency, frequency range, and sound type (whether pure tonelike or highly modulated). Forest habitats differ from grass and edge in that a narrow range of frequencies (1,585-2,500 Hz) has lower sound attenuation than lower or higher frequencies. Attenuation increases rapidly above 2,500 Hz. Bird sounds from species occurring at the lower forest levels were found to be predominantly pure tonelike with a frequency emphasized averaging 2,200 Hz, conforming to the predictions based on sound propagation tests. The edge habitat is characterized by a wide range of frequencies having a generally similar attenuation rate. Pure tone and random noise band sounds did not diffe...
This paper describes a concept, not altogether new but largely neglected, that should lead to a greater understanding of the information contained in certain classes of vocal communication signals of birds and mammals. The concept is based on empirical data, first pointed out by Collias (1960, p. 382), showing that natural selection has resulted in the structural convergence of many animal sounds used in "hostile" and "friendly" contexts. Simply stated, birds and mammals use harsh, relatively low-frequency sounds when hostile and higherfrequency, more pure tonelike sounds when frightened, appeasing, or approaching in a friendly manner. Thus, there appears to be a general relationship between the physical structures of sounds and the motivation underlying their use. I hope to develop the idea that this relationship has had a far greater influence on the evolution of animal communication systems than has hitherto been discussed. I will discuss the idea that there exist motivation-structural rules (MS) governing the physical structure of close contact sounds in animal communication systems. The greatest value of the MS concept is that it provides the opportunity to compare the evolution of vocal communication in any species against an abstract concept. The adaptive nature of communication systems against varying backgrounds of environment, social system, and competition will appear in clear relief.
In their natural West African rainforest habitat, Diana monkeys continuously produce high rates of a close-range clear-sounding call, but the function of this behaviour is unknown. In other primate species, close-range calls are typically given in socially relevant situations, for example, to gain access to grooming partners or food. Quite contrarily, we tested a number of hypotheses and found that Diana monkey 'clear' calls primarily function to avoid predation. Call rates were significantly elevated when predation threat was high, for instance when the visibility was poor, when the group spread was large, when the group was not associated with other monkey species, or after alarm calls. Call rates were not significantly elevated, however, in circumstances of high social competition, for instance when the group spread was small, during resting phases, while feeding on clumped food sources, or when foraging in the periphery where inter-group encounters were more likely to occur. Calling was contagious in that calls typically elicited vocal responses from out-of-sight group members within a few seconds. Because of this, callers can effectively monitor a much larger area than is visually accessible to single individuals, suggesting that Diana monkey clear calls act as an essential element in a mutualistic system of co-ordinated vigilance.
Tested the relations between acoustic parameters and social context in 4 common marmosets separated from their mates. Call duration, peak frequency, frequency range, median frequency, and start modulation increased with decreasing sensory information about mates. Ss' nonvocal behavior was also modified by a decrease in sensory information about their mates. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Makes a quantitative comparison of the frequency of usage of vocal signals in the chimpanzee and the gorilla and discusses the emphasis in these species on graded vocal sounds. Data are taken from the author's 2,656 tape-recorded vocalizations of individual chimpanzees and are compared with D. Fossey's (1972) data on a similar sample of mountain gorilla vocalizations. The findings are used to relate vocal behavior to social organization in the two species. A review is made of human categorical perceptual processing of graded sounds occurring in normal speech. A possible model is derived for analyzing vocal perception in higher nonhuman primates which make frequent use of graded vocalizations in their social behavior. (3 p ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The cotton-top tamarin (Saguinus oedipus oedipus) has an extensive vocal repertoire which is derived from the variation of two basic elements and the sequential combination of those elements. A distinctive features analysis demonstrated at least 8 phonetic variants of a short, frequency modulated call (chirp) and five longer constant frequency calls (whistles). The call variants do not describe points on a single motivational continuum, but rather each variant represents a different message. A simple grammar is presented to describe all sequences of calls. While most of the call sequences fit the definition of phonetic syntax, at least two sequences appear to be exemplars of lexical syntax. Call structures are modified to provide increasing cues for auditory localization as animals are farther apart from each other. Comparisons of calls of S. o. oedipus with those of other callitrichids show a gradual divergence of call type with increasing geographic and phylogenic separation.
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.
This study examines whether individual adult male blue monkeys (Cercopithecus mitis stuhlmanni) can be identified through acoustic analysis of their “pyow” calls. It is possible to reliably assign the pyow call of the blue monkeys of Kibale Forest, Uganda, to the individual caller based on the acoustic properties of the vocalization. Analysis of pyows made by a recognizable male over a 10-yr period shows that the acoustic properties of one individual's pyow call can remain relatively constant over time. Acoustic analysis of pyow calls may provide a relatively easy and reliable method to document tenure lengths of adult male blue monkeys resident in groups. Similar analyses of the loud calls of other species of primates may, likewise, prove to be useful in documenting long-term membership. © 1992 Wiley-Liss, Inc.
Many nonhuman primates produce species-typical loud calls used to communicate between and within groups over long distances.
Given their observed spacing functions, primate loud calls are likely to show acoustic adaptations to increase their propagation
over distance. Here we evaluate the hypothesis that primates emit loud calls at relatively low sound frequencies to minimize
their attenuation. We tested this hypothesis within and between species. First, we compared the frequencies of loud calls
produced by each species with those of other calls from their vocal repertoires. Second, we investigated the relationship
between loud call frequency and home range size across a sample of primate species. Comparisons indicated that primates produce
loud calls at lower frequencies than other calls within their vocal repertoires. In addition, a significant negative relationship
exists between loud call frequency and home range size among species. The relationship between call frequency and range size
holds after controlling for the potentially confounding effects of body size and phylogeny. These results are consistent with
the hypothesis that nonhuman primates produce loud calls at relatively low frequencies to facilitate their transmission over
long distances.
Vocal communication in wild long-tailed macaques (Macaca fascicularis) is described in terms of (1) a preliminary vocal repertoire
and the situations in which calls occur in the natural habitat of this species and (2) quantitative measurement of the natural
occurrence of calls in the field. Although a number of calls are relatively discrete (e.g., a male loud call), gradation is
pronounced for both wide-spectrum (“harsh”) and narrow-spectrum (“clear”) vocal signals. Thirteen general types of harsh calls
are identified provisionally as elements of the vocal repertoire. The exact number of discrete clear calls contributing to
the vocal repertoire could not be ascertained precisely, but these calls were classified operationally into six broadly acoustically
different classes in order to measure natural vocal behavior. Vocalizations tended to occur in temporal “clusters” during
sample, periods. Narrow-band clear or “coo” calls were more frequently performed by macaques than wide-band harsh calls. The
possible functional implications of the correlated occurrence of multiple vocal signals are discussed.
One of the most prominent behavioural features of many forest primates are the loud calls given by the adult males. Early observational studies repeatedly postulated that these calls function in intragroup spacing or intergroup avoidance. More recent field experiments with Diana monkeys (Cercopithecus diana) of Ta Forest, Ivory Coast, have clearly shown that loud male calls function as predator alarm calls because calls reliably (1) label different predator classes and (2) convey semantic information about the predator type present. Here, I test the alarm call hypothesis another primate, the Campbell's monkey (C. campbelli). Like Diana monkeys, male Campbell's monkeys produce conspicuous loud calls to crowned hawk eagles (Stephanoaetus coronatus) and leopards (Panthera pardus), two of their main predators. Playback experiments showed that monkeys responded to the predator category represented by the different playback stimuli, regardless of whether they consisted of (1) vocalisations of the actual predators (crowned hawk eagle shrieks or leopard growls), (2) alarm calls to crowned hawk eagles or leopards given by other male Campbell's monkeys or (3) alarm calls to crowned hawk eagles or leopards given by sympatric male Diana monkeys. These experiments provide further evidence that non-human primates have evolved the cognitive capacity to produce and respond to referential labels for external events.
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.
In many species, call recipients respond to food-associated calls by approaching the signaller. For this reason, most studies of food-associated calls focus on the benefits to a signaller of attracting a particular audience to a food source. Although call recipients respond as if they have been informed about the location of a food source, it is not necessarily the case that the primary function of food-associated calls is to inform others. I combined naturalistic observations and food placement experiments to investigate the environmental and social influences on call production in white-faced capuchin monkeys to assess other possible functions of food-associated calls. Individuals did not call under the circumstances predicted by an information-sharing hypothesis. The quantity of food and the age–sex composition of the audience did not influence call production, but food type did. Individuals produced more food-associated calls when they discovered fruit compared with insects or eggs. Results of observations of social interactions after food discovery indicated another possible function of food-associated calls. Individuals who called when they discovered food were less likely to be approached by others who were in visual contact than individuals who remained silent. Individuals who did not call when they discovered food were more likely to call subsequently if a higher-ranking, as opposed to a lower-ranking, animal approached them. Furthermore, individuals who called when approached by higher-ranking animals were less likely to receive aggression than individuals who did not call. Therefore, food-associated calls may function to announce food ownership, thereby decreasing aggression from other individuals.
Free-ranging vervet monkeys grunt to each other in a variety of social situations: when approaching a dominant or subordinate individual, when moving into a new area of their range, or when observing another group. Like other non-human primate vocalizations, these grunts have traditionally been interpreted as a single, highly variable call that reflects the arousal state of the signaller. Field playback experiments suggest, however, that what humans initially perceive as one grunt the monkeys perceive as at least four. Each grunt carries a specific meaning that seems to depend more on its acoustic properties than on the context in which it occurs. Results suggest that the vocalizations given by monkeys during social interactions may function in a rudimentary representational manner, as if to designate objects or events in the external world.
We present the results of an experimental study of territoriality among monogamous lar gibbons (Hylobates lar), scoring vocal and movement responses to field playback of their loud calls. Playback of neighbouring groups' male-female duets on territory borders, and of these duets and music controls in territory centres, indicated a general territorial response. Responses to playback of a strange male's solo and of a strange female's solo in territory centres indicated that resident males would evict deeply intruding males and pairs but not necessarily females, and that resident females would evict deeply intruding females but probably not males or pairs. Vocal responses also implied that, although males carry the burden of routine territory defence in border disputes involving chases and special calls, the female part of the daily duet also contributes to routine exclusion of outside females. Responses of lar females to playback of the solo of a female capped gibbon (H. pileatus) suggested that the females of one species cannot sex the calls of females of the other species. This could partly account for the existence of bigamous mixed-species groups at the interface between the two species. This result also implies that female calls contribute to routine exclusion of conspecific females, and thus to the maintenance of monogamy.
A central issue in studies of vocalizations of non-human primates is the extent of their plasticity. Japanese macaques, Macaca fuscata, frequently utter coo calls and exchange these calls with other group members to maintain contact vocally. I conducted a playback experiment to examine whether monkeys that respond vocally match the acoustic features of their reply to those of the calls they have heard. Six to eight stimulus calls with different acoustic properties in terms of fundamental frequency components were played back to each of seven females, in an attempt to elicit replies from the subjects. There were significant positive regressions of the frequency range of stimuli with that of the replies. Japanese macaques thus matched some of the acoustic features of their replies to those of the preceding calls, suggesting that they might be able to modify the acoustic features of their calls according to the features of the prior calls of another group member.Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.
(from the journal abstract) Capuchin monkeys (Cebus capucinus) are threatened by several types of predators, including various aerial, arboreal and terrestrial predators. Whenever they encounter one of these threats, capuchin monkeys show different escape strategies and utter one of several types of alarm calls. These alarm calls constitute two acoustic categories, each of which is composed of several subtypes: the first category is composed of alarm calls given in response to aerial predators, humans and other capuchin monkeys, and the second is composed of alarm calls given in response to terrestrial predators and snakes. However, within these two broad categories the different subtypes of alarm calls appeared to show a graded continuum with transitions in between. Therefore, we performed an acoustic analysis to determine whether alarm calls between and within categories are characterized by distinct acoustic features. First, the two broad alarm call categories differed in call structure. Second, alarm calls of the first category, given in response to aerial predators, humans and other monkeys, differed in several acoustic variables and thus may convey context-specific information about the type of threat to listeners. Third, alarm calls of the second category, given in response to terrestrial predators and snakes, also differed in several acoustic variables; however, variants of these alarm calls are also given in response to caiman as well as during highly aggressive interactions between conspecifics and thus may not convey specific information about the type of predator or the threat to listeners. Capuchin monkey alarm calls may therefore have the potential to be functionally referential, general and/or urgency-based signals. Future research using detailed playback experiments with alarm calls and analyses of listeners' responses is required. (PsycINFO Database Record (c) 2005 APA, all rights reserved).
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 diÄerences in relation to these variables, we extracted a suite of acoustic parameters from digitized calls and applied discriminant function ana- lyses. The barks constitute a graded continuum, ranging from a tonal, harmoni- cally 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 signifi- cant diÄerences 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 diÄerent from contact barks, indicating that the calls vary along diÄerent dimensions. Finally, there are consistent, significant diÄer- ences among diÄerent individuals' calls. However, individual identity in one call type cannot directly be inferred from knowledge of the individuals' call character- istics 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 discri- minate between alarm and contact barks, and classify calls according to context and/or acoustic similarity will be described in a subsequent paper.
Thesis (Ph. D)--Harvard University, 1977.
SYNOPSIS. The ability of animals to recognize and classify others reflects the selective pressures acting on individuals within a particular social framework. Data on recognition therefore allow us to consider social structure from the animal's point of view. Here we review data on recognition within groups of free-ranging vervet monkeys, and present evidence of recognition across groups. Within groups, experiments suggest that animals may proceed beyond simple discriminations of kin and non-kin to create a taxonomy in which group members are both distinguished as individuals and grouped into higher order units, apparently on the basis of matrilineal kinship. Across groups, observation indicates that male transfer is non-random, and that the exchange of males between groups is correlated with reduced aggression. Playback experiments demonstrate that monkeys associate the vocalizations of particular individuals with particular groups. We conclude that the social organization of vervet monkeys is best regarded as a “community” of groups, within which individuals recognize each other and share a high degree of genetic relatedness despite the maintenance of otherwise discrete social units.
E. S. Morton proposed that, in birds and mammals, individuals tend to produce low-frequency atonal vocalizations in highly aggressive situations, whereas they typically produce high-frequency tonal vocalizations during nonaggressive or fearful situations. This hypothesis, referred to as the "motivation-structural (MS) rules," is based on two assumptions: the frequency of a vocalization is negatively correlated with body weight, and large animals are dominant over smaller animals, and thus aggressive vocalizations tend to have a lower pitch than fearful vocalizations. The relationship between body weight and frequency is examined using data on 36 nonhuman primate species representing 23 genera and 474 vocalizations. Results show that there is a statistically significant negative correlation between body weight and frequency: larger species produce relatively lower-pitched vocalizations than smaller species. A test of Morton's MS rules provided overall support for the predicted relationship between motivational state and frequency (i.e., high-frequency calls were produced by fearful individuals, and low-frequency calls were produced by aggressive individuals) but no support for the expected relationship between motivational state and tonality. However, the motivational state-frequency pairing was confounded by the fact that some taxonomic groups (Platyrrhini and Catarrhini) showed a much stronger level of association than other groups (Prosimii and Hominoidea). In summary, therefore, the nonhuman primate data provide only partial support for MS rules. At least three factors may have influenced the outcome of the current test. First, in some species, motivational state may be more closely associated with other acoustic parameters than absolute frequency and tonality. Second, the acoustic structure of nonhuman primate vocalizations is, at least in some cases, more closely associated with an external referent than with the caller's internal state. And third, features of the species-typical habitat have had direct selective effects on signal structure, optimizing for effective propagation through the environment.
Fruit color and size are significant determinants of food choice in mammals and birds, but hardness, an important physical property of fruit and seeds, has generally been overlooked as a determinant of food choice in studies of mammalian foraging behavior. Two methods were used to determine fruit hardness during a field study of two sympatric primates, the black spider monkey (Ateles paniscus) and the bearded saki monkey (Chiropotes satanas) in Surinam. We measured both puncture resistance of fruit pericarp and crushing resistance of seeds. Puncture resistance of the pericarp of some fruit opened by Chiropotes was as much as 15 times greater than that of all fruit successfully opened by Ateles. In contrast, crushing resistance of species of seeds masticated by Chiropotes was significantly lower than that of seeds swallowed by Ateles. These data demonstrate that hardness of both fruit pericarp and seed may play a significant role in food choice among sympatric vertebrates. Measurements of both puncture resistance of the pericarp and crushing resistance of the seed are necessary for understanding the significance of fruit hardness in these primates.
Two hundred and fifty vocalizations of the squirrel monkey (Saimiri sciureus) were selected for spectrographic analysis from a total of 200 hrs. of tape recordings. The vocalizations were classified into six groups according to their physical characteristics. Both intra and intergroup variability of calls was observed. Calls of similar shape were found to have similar functions. Thus each group of calls could be characterized by a functional designation. The functional significance of calls was determined by qualitative and quantitative observations. Four methods were employed: 1. stereotyped vocalizations were elicited by visual stimuli; 2. motor and vocal reactions were evoked through adequate vocal signals; 3. vocalizations were observed when external conditions were held constant and internal factors were permitted to vary; 4. vocal events were related to the total social situation. By these methods the complexity as well as the specificity of the vocal communication system is demonstrated and its evolutionary significance is discussed.
This study provides an overview of the vocalizations of Barbary macaques, Macaca sylvanus. Spectrographic displays of calls are presented along with photographs of the accompanying facial gestures. We give a general description of the contexts in which the different calls are uttered, with special regard to the age and sex of the caller. The vocal repertoire of Barbary macaques mainly consists of screams, shrill barks, geckers, low-frequency pants and grunts, with gradation occurring within and between call types. The spectrograms document that typically, Barbary macaques produce series of several consecutive calls. The influence of habitat, social structure and phylogenetic descent on the morphology of the repertoire and call diversity are discussed in comparison to other species.
This study identifies populations currently classified as Allen's galago (Galago alleni) at ten locations in Gabon, Cameroon and Bioko Island. Morphological diversity was evident both within and between populations. Attention to the loud calls revealed three distinct vocal profiles which are consistent within biogeographical regions. This work is based on the Recognition Concept of Species which refers to a Specific Mate Recognition System. Galagos rely less on visual signals than diurnal primates and recognise each other principally by means of auditory and olfactory signals. Galagos possess repertoires of loud calls relating to contact and alarm which are thought to be species-specific. Other studies of nocturnal prosimians (galagos, tarsiers) have demonstrated that the unique loud call repertoires are reliable indicators of species boundaries; whereas characters such as body size and pelage coloration are highly variable, even within populations. The vocal data in this study provide evidence of at least three acoustic forms of galago within the Allen's group which are predicted to represent three distinct species: the Allen's form on Bioko Island and south-west Cameroon, the Gabon form in southern Cameroon and northern Gabon and the Makandé form in Gabon south of the Ogooué river. Some populations may be vulnerable to extinction due to limited distributions and habitat destruction.