'Food' Calls Produced By Adult Female Rhesus (Macaca Mulatta) and Japanese (M. Fuscata) Macaques, Their Normally-Raised Offspring, and Offspring Cross-Fostered Between Species

Abstract

Abstract We tested a recent claim that rhesus and Japanese macaque offspring cross-fostered between species exhibit vocal learning by producing 'food' calls typical of their adoptive rather than their genetic species (MASATAKA & FUJITA, 1989). Our study population consisted of four groups of socially-reared animals housed outdoors - two of each species. Food calls produced by adult female rhesus and Japanese macaques did not differ at the species level, although individual differences were clearly present. Food calls produced by normally raised offspring differed both between individuals and between species. In spite of statistically significant differences, however, immatures in the two species still showed substantial overlap on every acoustic feature that was measured. Evidence from four cross-fostered offspring was equivocal. Two rhesus macaques raised in Japanese macaque social groups produced calls that were typical of their own species. Some measurements from calls produced by two cross-fostered Japanese macaques fell closer to mean values for normal rhesus than for those of their own species. However, these measurements were still within the observed range of variation shown by normally raised Japanese macaques. We conclude that food calling behavior of cross-fostered Japanese macaques may have shown modification, but that any such effect was not based on a species-specific adult model. Given the variability of these sounds and the lack of species differences in adult female vocalizations, food calls do not present a good opportunity to test for vocal learning in cross-fostered rhesus and Japanese macaques.