Age Gradations in Vocalization and Body Weight in Japanese Monkeys (Macaca fuscata)

Abstract

449 syllables in 174 food calls of Japanese monkeys of various ages were analyzed spectrographically. The fundamental frequency bands were divided into 55 frequency modulation patterns. The percentage of harsh syllables changed with age class among adults. Although the duration of syllables did not change with age, the maximum fundamental frequency and the minimum fundamental frequency showed age-related changes. Both were distinctly decreased by 6–8 years of age and thereafter the decline was far more gradual. Body weight also increased up to 6 years of age for females and 8 years for males, thereafter stabilizing for both sexes. The matching in age-related changes between fundamental frequency and body weight indicates that it is increase in size of the vocal folds with physical growth that lowers the fundamental frequency.

An Overview of the Barbary Macaque, Macaca sylvanus, Vocal Repertoire

“…To date, there are few comprehensive studies on the vocal repertoires of other macaques species, for instance Green's study on Japanese macaques, M. fuscata [10], Palombit's description of the vocal repertoire of on long-tailed macaques, M. fascicularis [9], or Hohmann's overview of the calls of the lion-tailed macaques, M. silenus [11]. Most other studies addressing macaque vocal behaviour dealt with more specific aspects, for instance the use of 'food calls' in toque macaques, M. sinica [48], acoustic variation within and between contexts [32,49], or relation to age and sex [50][51][52], and individual differences in vocalizations [53][54][55]. It is worth noting that in contrast to some other macaque species [48,56], we never observed any vocalizations in the context of encountering food or highly preferred food.…”

Do age- and sex-related variations reliably reflect body size in non-human primate vocalizations? A review

“…Hauser (1989) Inter-unit interval duration Duration of the interval between two units in a call (ms) Seyfarth and Cheney (1986) Maximum frequency range Maximum frequency range (highest frequency -lowest frequency) over all time segments (Hz) Hammerschmidt et al (1994), Hammerschmidt and Fischer (1998) and Mean gap length Mean duration of the parts of the call where the amplitude is less than 20% of the mean maximum amplitude across all time segments (ms) Hammerschmidt et al (2000) Mean local modulation of central frequency Floating average describing how much the central frequency differs from its linear trend Hammerschmidt et al (1994) and Hammerschmidt and Fischer (1998) Mean local modulation of dfb Floating average describing how much the first dominant frequency band differs from its linear trend Hammerschmidt et al (1994) and Hammerschmidt and Fischer (1998) Mean peak frequency Mean value across all time segments of the peak frequency (Hz) Hammerschmidt et al (2000) Mean range Mean difference between the highest and the lowest frequencies across all time segments in the call (Hz) Hammerschmidt et al (2000) and Hammerschmidt et al (2001) Mean repertoire frequency Mean over the whole repertoire of a species of the first dominant frequency band or fundamental frequency (Hz) Hauser (1993) Minimum fundamental frequency Minimum fundamental frequency in all time segments (Hz) Inoue (1988) Modulation of the fundamental frequency Floating average describing how much the fundamental frequency differs from its linear trend…”

Acoustically Dimorphic Advertisement Calls Separate Morphologically and Genetically Homogenous Populations of the Grey Mouse Lemur (Microcebus murinus)

“…Intraspecific variability of context-homologous primate vocalisations was not only found between populations, but can also be correlated with differences in body size [32][33][34], age [32,35,36] sex [35,37], social relations (including dominance relationships, for reviews see e.g. [38][39][40][41]), motivation [42] and individual variation [43][44][45].…”