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Fischer, J., Cheney, D. L., & Seyfarth, R. M. (2000). Development of infant baboons' responses to graded bark variants. Proc Biol Sci, 267(1459), 2317–2321.
Abstract: We studied the development of infant baboons' (Papio cynocephalus ursinus) responses to conspecific 'barks' in a free-ranging population in the Okavango Delta, Botswana. These barks grade from tonal, harmonically rich calls into calls with a more noisy, harsh structure. Typically, tonal variants are given when the signaller is at risk of losing contact with the group or a particular individual ('contact barks'), whereas harsh variants are given in response to predators ('alarm barks'). We conducted focal observations and playback experiments in which we presented variants of barks recorded from resident adult females. By six months of age, infants reliably discriminated between typical alarm and contact barks and they responded more strongly to intermediate alarm calls than to typical contact barks. Infants of six months and older also recognized their mothers by voice. The ability to discriminate between different call variants developed with increasing age. At two and a half months of age, infants failed to respond at all, whereas at four months they responded irrespective of the call type that was presented. At six months, infants showed adult-like responses by responding strongly to alarm barks but ignoring contact barks. We concluded that infants gradually learn to attach the appropriate meaning to alarm and contact barks.
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Seyfarth, R. M., & Cheney, D. L. (1992). Meaning and mind in monkeys. Sci Am, 267(6), 122–128.
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Seyfarth, R. M., Cheney, D. L., & Marler, P. (1980). Monkey responses to three different alarm calls: evidence of predator classification and semantic communication. Science, 210(4471), 801–803.
Abstract: Vervet monkeys give different alarm calls to different predators. Recordings of the alarms played back when predators were absent caused the monkeys to run into trees for leopard alarms, look up for eagle alarms, and look down for snake alarms. Adults call primarily to leopards, martial eagles, and pythons, but infants give leopard alarms to various mammals, eagle alarms to many birds, and snake alarms to various snakelike objects. Predator classification improves with age and experience.
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Hostetter, A. B., Cantero, M., & Hopkins, W. D. (2001). Differential use of vocal and gestural communication by chimpanzees (Pan troglodytes) in response to the attentional status of a human (Homo sapiens). J. Comp. Psychol., 115(4), 337–343.
Abstract: This study examined the communicative behavior of 49 captive chimpanzees (Pan troglodytes), particularly their use of vocalizations, manual gestures, and other auditory- or tactile-based behaviors as a means of gaining an inattentive audience's attention. A human (Homo sapiens) experimenter held a banana while oriented either toward or away from the chimpanzee. The chimpanzees' behavior was recorded for 60 s. Chimpanzees emitted vocalizations faster and were more likely to produce vocalizations as their 1st communicative behavior when a human was oriented away from them. Chimpanzees used manual gestures more frequently and faster when the human was oriented toward them. These results replicate the findings of earlier studies on chimpanzee gestural communication and provide new information about the intentional and functional use of their vocalizations.
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Rendall, D., Cheney, D. L., & Seyfarth, R. M. (2000). Proximate factors mediating “contact” calls in adult female baboons (Papio cynocephalus ursinus) and their infants. J Comp Psychol, 114(1), 36–46.
Abstract: “Contact” calls are widespread in social mammals and birds, but the proximate factors that motivate call production and mediate their contact function remain poorly specified. Field study of chacma baboons (Papio cynocephalus ursinus) revealed that contact barks in adult females were motivated by separation both from the group at large and from their dependent infants. A variety of social and ecological factors affect the probability of separation from either one or both. Results of simultaneous observations and a playback experiment indicate that the contact function of calling between mothers and infants was mediated by occasional maternal retrieval rather than coordinated call exchange. Mothers recognized the contact barks of their own infants and often were strongly motivated to locate them. However, mothers did not produce contact barks in reply unless they themselves were at risk of becoming separated from the group.
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Fischer, J., Hammerschmidt, K., Cheney, D. L., & Seyfarth, R. M. (2002). Acoustic features of male baboon loud calls: influences of context, age, and individuality. J Acoust Soc Am, 111(3), 1465–1474.
Abstract: The acoustic structure of loud calls (“wahoos”) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer “hoo” duration, and a relatively louder “hoo” portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained.
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Cheney, D. L., Seyfarth, R. M., & Silk, J. B. (1995). The responses of female baboons (Papio cynocephalus ursinus) to anomalous social interactions: evidence for causal reasoning? J Comp Psychol, 109(2), 134–141.
Abstract: Baboons' (Papio cynocephalus ursinus) understanding of cause-effect relations in the context of social interactions was examined through use of a playback experiment. Under natural conditions, dominant female baboons often grunt to more subordinate mothers when interacting with their infants. Mothers occasionally respond to these grunts by uttering submissive fear barks. Subjects were played causally inconsistent call sequences in which a lower ranking female apparently grunted to a higher ranking female, and the higher ranking female apparently responded with fear barks. As a control, subjects heard a sequence made causally consistent by the inclusion of grunts from a 3rd female that was dominant to both of the others. Subjects responded significantly more strongly to the causally inconsistent sequences, suggesting that they recognized the factors that cause 1 individual to give submissive vocalizations to another.
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Pepperberg, I. M., & Brezinsky, M. V. (1991). Acquisition of a relative class concept by an African gray parrot (Psittacus erithacus): discriminations based on relative size. J Comp Psychol, 105(3), 286–294.
Abstract: We report that an African gray parrot (Psittacus erithacus), Alex, responds to stimuli on a relative basis. Previous laboratory studies with artificial stimuli (such as pure tones) suggest that birds make relational responses as a secondary strategy, only after they have acquired information about the absolute values of the stimuli. Alex, however, after learning to respond to a small set of exemplars on the basis of relative size, transferred this behavior to novel situations that did not provide specific information about the absolute values of the stimuli. He responded to vocal questions about which was the larger or smaller exemplar by vocally labeling its color or material, and he responded “none” if the exemplars did not differ in size. His overall accuracy was 78.7%.
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Owren, M. J., Seyfarth, R. M., & Cheney, D. L. (1997). The acoustic features of vowel-like grunt calls in chacma baboons (Papio cyncephalus ursinus): implications for production processes and functions. J Acoust Soc Am, 101(5 Pt 1), 2951–2963.
Abstract: The acoustic features of 216 baboon grunts were investigated through analysis of field-recorded calls produced by identified females in known contexts. Analyses addressed two distinct questions: whether the acoustic features of these tonal sounds could be characterized using a source-filter approach and whether the acoustic features of grunts varied by individual caller and social context. Converging evidence indicated that grunts were produced through a combination of periodic laryngeal vibration and a stable vocal tract filter. Their acoustic properties closely resembled those of prototypical human vowel sounds. In general, variation in the acoustic features of the grunts was more strongly related to caller identity than to the social contexts of calling. However, two acoustic parameters, second formant frequency and overall spectral tilt, did vary consistently depending on whether the caller was interacting with an infant or participating in a group move. Nonetheless, in accordance with the general view that identity cueing is a compelling function in animal communication, it can be concluded that much of the observed variability in grunt acoustics is likely to be related to this aspect of signaling. Further, cues related to vocal tract filtering appear particularly likely to play an important role in identifying individual calling animals.
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Stober, M., & Geiger, J. F. (1975). [Lamenting “moaning” in domestic cattle]. Dtsch Tierarztl Wochenschr, 82(1), 10–13.
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