First wild evidence of neonate nipple preference and maternal cradling laterality in Old World monkeys: A preliminary study from Rhinopithecus roxellana

Although captive or free-ranging settings offer a more controlled environment for assessing non-human primate laterality, research on wild populations provides evidence of how laterality is affected by natural environmental conditions and, thus may yield potential insights into the evolution of laterality. This study of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) constitutes the first report on asymmetric patterns of early mother–infant interactions among Old World monkeys in the wild. It was found that neonate nipple preference and maternal cradling laterality are both evident on the individual level. Although there is no significant group-level preference direction, the group preference strength on both measures is evident. Moreover, neonate nipple preference is not significantly correlated with maternal cradling laterality on either LBI scores or the direction (LBI scores: r = 0.174, p = 0.632; direction: r = 0.624, p = 0.054). Taken together, it is possible to suggest that wild R. roxellana show independent orientation laterality from the first week of life.