Patterns and effects of reactions to handling by infant Japanese macaques in Yakushima

Abstract

While infant handling has been reported in primate species, little has been reported about the infants’ reactions to handling. Here, we present a field study of infant handling and infants’ reactions after being handled in Japanese macaques in Yakushima (Macaca fuscata yakui). We tracked 12 infants born in a large macaque group for a year after the birth of each infant and continuously recorded the time and type of infant handling and the infant’s reaction. We found that infants showed certain patterns in their reactions to handling they were targeted for: infants showed quicker reactions to certain types of handling. Some types of the reaction occurred soon after handling, while others occurred more slowly. Long-lasting handling sometimes made infants squeak, even if it was not rough. We also found that vocal responses were the most effective in attracting mothers’ attention. These findings indicate that infants’ behaviors toward handling may have different meanings; infants may express their own conditions that vary depending on the different handling situations they are involved in. As an attempt to highlight infants’ autonomy, this study suggests paying attention to infants even in infant-directed behaviors.