Vocalization
Do age- and sex-related variations reliably reflect body size in non-human primate vocalizations? A review
In vocal communication, the mechanisms of sound production are well understood. The length of the vocal folds determines the minimum fundamental frequency, while the size and the shape of the vocal tract affect its filtering characteristics and hence, the resonant frequencies. Both measures—vocal fold length and vocal tract length—are related to body size and therefore, acoustic features are expected to vary with body size. Because direct measures of body size are difficult to obtain from free-ranging animals, age and sex have often been used as proxies. We surveyed studies which included direct measures of size or weight, and also studies in which only age and/or sex differences were examined. The main purpose was to examine whether age- and sex-related variations in acoustic features meet the predictions generated from our knowledge about sound production. Our survey revealed that compared to smaller animals, larger animals utter longer calls, with a lower fundamental frequency, with smaller formant dispersion, and with the energy concentrated in lower frequencies. Age and sex reliably reflect the influence of body size on acoustic features when gross size differences are examined. However, within age- and sex classes, this relationship may break down. In addition to body size, other factors such as internal state or social context may also influence the structure of vocal signals and highlight the richness of information in calls that is potentially available to listeners.
Keywords Primates - Sound production - Body size - Age - Sex
—————————————————————————————-
Acoustic Features of Female Chacma Baboon Barks
We studied variation in the loud barks of free-ranging female chacma baboons (Papio cynocephalus ursinus) with respect to context, predator type, and individuality over an 18-month period in the Moremi Game Reserve, Botswana. To examine acoustic differences in relation to these variables, we extracted a suite of acoustic parameters from digitized calls and applied discriminant function analyses. The barks constitute a graded continuum, ranging from a tonal, harmonically rich call into a call with a more noisy, harsh structure. Tonal barks are typically given when the signaler is at risk of losing contact with the group or when a mother and infant have become separated (contact barks). The harsher variants are given in response to large predators (alarm barks). However, there are also intermediate forms between the two subtypes which may occur in both situations. This finding is not due to an overlap of individuals’ distinct distributions but can be replicated within individuals. Within the alarm bark category, there are significant differences between calls given in response to mammalian carnivores and those given in response to crocodiles. Again, there are intermediate variants. Both alarm call types are equally different from contact barks, indicating that the calls vary along different dimensions. Finally, there are consistent, significant differences among different individuals’ calls. However, individual identity in one call type cannot directly be inferred from knowledge of the individuals’ call characteristics in the other. In sum, the barks of female baboons potentially provide rich information to the recipients of these signals. The extent to which baboons discriminate between alarm and contact barks, and classify calls according to context and/or acoustic similarity will be described in a subsequent paper.
—————————————————————————————
* Julia Fischer,
* Kurt Hammerschmidt,
* Dorothy L. Cheney &
* Robert M. Seyfarth
*
Department of Biology, University of Pennsylvania, Philadelphia; Department of Psychology, University of Pennsylvania, Philadelphia; Deutsches Primatenzentrum, Abteilung Neurobiologie, Göttingen
Correspondence to: Julia Fischer, Max-Planck Institute for Evolutionary Anthropology, Inselstr. 22, D-04103 Leipzig, Germany. E-mail: fischer@eva.mpg.de
—————————————————————————————-
Dog barks reveal universal language
What do dog barks have in common with bird tweets and human baby cries? All appear to communicate basic emotions, such as fear, aggression and submission, in somewhat the same acoustic way, according to a new Applied Animal Behavior Science study that suggests a primitive communication system may unite virtually all mammals.
The theory could help explain why previous research has found that many mammals, including humans, understand the vocalizations of different species.
For example, a Language Communication study determined young children can identify simple emotions conveyed in macaque calls. Other studies indicate that interacting individuals among African grey parrots and bonobos can agree on the object that’s likely referred to by a vocalization…
