VARIATIONS IN FUNDAMENTAL-FREQUENCY PEAK POSITION IN JAPANESE MACAQUE(MACAQUE FUSCATA) COO CALLS

Japanese macaques (Macaca fuscata) produce coo calls whose use in vari ous contexts is correlated with differences in the relative temporal p osition of the peak value of a call's fundamental frequency (Green, 19 75). Studies have produced conflicting results about both the location of the category boundary between smooth early high and smooth late hi gh coo subtypes and macaques perceptual sensitivity to variations in p eak position. In this study, fundamental frequency peak positions were measured in 578 coos produced by 8 captive adult female Japanese maca ques in order to test whether calls with peak positions close to eithe r of 2 hypothesized boundaries occurred at low rates. Overall, such ca lls were found to occur at rates equal to or higher than predicted by chance, Peak position varied more consistently between animals than by behavioral context. The results may indicate that peak position in co os does not form 2 distinct categories.