We addressed the possible role of genetic determinants and phylogenetic factors in stone handling variation, through comparative analyses of stone handling behavior at the subspecies and species levels. When comparing the two subspecies of Japanese macaques, Macaca fuscata fuscata, widely distributed in the Japanese archipelago, and M. f. yakui endemic to Yakushima, a small island at the southern limit of distribution of the species, we found that they did not notably differ in the stone handling repertoire, as well as the occurrence, form, and context of the behavior. Stone handling patterns varied as much between troops of the same subspecies as between subspecies themselves.

Second, the similarities in the occurrence, form, and context of stone handling behavior in rhesus macaques (Macaca mulatta) and long-tailed macaques (M. fascicularis) confirmed the prediction that closely related macaque species shared a behavioral propensity for stone handling [REPORT]

Overall, based on common behavioral predispositions in phylogenetically close taxa, and knowledge of genetic determinism, it is reasonable to consider that genetic and phylogenetic factors may not be key to explaining the observed inter-troop variability in the form of stone handling in macaques  [REPORT]