Acoustic And Olfactory Communication In Eastern Sifakas (Propithecus Sp.) And Rhesus Macaques (Macaca Mullata)
This dissertation contains three studies of acoustic and olfactory communication in several species of nonhuman primates. The first is a longitudinal study of "gecker" distress vocalizations in infant rhesus monkeys (Macaca mullata) during the first 24 months of life. Acoustic and behavioral analyses revealed age, sex, and maternal response differences across several temporal, spectral, and amplitude measures, but little context-specific acoustic differentiation. Female geckers showed higher spectral peaks and bout durations, while male geckers were higher in amplitude and less noisy. Developmentally, gecker usage peaked at four months of age for both sexes, with male geckers nonetheless tending to occur at younger ages than those of females. In sum, gecker acoustics appear to be well designed to draw the attention of mothers and other listeners, while also potentially becoming aversive. The second study examines the acoustic structure and function of "zzuss" vocalizations in wild silky sifakas (Propithecus candidus) in northeastern Madagascar. Acoustically, the calls combined separate turbulent noise and tonal components, often including frequency jumps and rapid, highly frequency-modulated components. Although silky sifakas are sexually monomorphic, male and female zzuss calls were acoustically different, most importantly in fundamental frequency and amplituderelated features. All acoustic measures differed between individuals, with fundamental frequency related variables again playing the largest role. Overall, zzuss calls are multi-function vocalizations used both for terrestrial disturbance and group coordination. They are shaped for salience, localizability, and caller identification, rather than to have word-like meaning. The final study examines non-nutritive tree gouging by wild silky sifakas (P. candidus) and Milne-Edwards' sifakas (P. edwardsi). Species differences were found in gouge mark morphology. Dominant males had longer gouge marks and gouged most frequently, with seasonal peaks just before and during the mating season. The resource gouging hypothesis was tested and supported in silky sifakas. A multiple regression analysis revealed that the number of gouges per tree species was predicted by the percentile rank of those species as food tree species and sleep tree species. Gouging appears to be an honest species specific signal of male status which may promote scent longevity and attract the visual attention of conspecifics.
Silky sifaka; Propithecus candidus; Rhesus macaque; Macaca mullata; lemur; Madagascar; vocalizations; scent mark
Johnston, Robert Elliott
Arcadi, Adam C.; Cutting, James Eric; Owren, Michael J.
Ph. D., Psychology
Doctor of Philosophy
dissertation or thesis