title: Free-ranging macaque mothers exaggerate tool-using behavior when observed by offspring.
abstract: The population-level use of tools has been reported in various animals. Nonetheless, how tool use might spread throughout a population is still an open question. In order to answer that, we observed the behavior of inserting human hair or human-hair-like material between their teeth as if they were using dental floss in a group of long-tailed macaques (Macaca fascicularis) in Thailand. The observation was undertaken by video-recording the tool-use of 7 adult females who were rearing 1-year-old infants, using the focal-animal-sampling method. When the data recorded were analyzed separately according to the presence/absence of the infant of the target animal in the target animal's proximity, the pattern of the tool-using action of long-tailed adult female macaques under our observation changed in the presence of the infant as compared with that in the absence of the infant so that the stream of tool-using action was punctuated by more pauses, repeated more often, and performed for a longer period during each bout in the presence of the infant. We interpret this as evidence for the possibility that they exaggerate their action in tool-using so as to facilitate the learning of the action by their own infants.
authors.affiliation: Primate Research Institute, Kyoto University, Inuyama, Japan. masataka@pri.kyoto-u.ac.jp
authors.forename: Nobuo
authors.initials: N
authors.lastname: Masataka
authors.forename: Hiroki
authors.initials: H
authors.lastname: Koda
authors.forename: Nontakorn
authors.initials: N
authors.lastname: Urasopon
authors.forename: Kunio
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D005260:Female; D007858:Learning; D008251:Macaca; D008425:Maternal Behavior; D009035:Mothers; D053001:Tool Use Behavior