Laterality of tail wrapping in golden snub-nosed monkeys (Rhinopithecus roxellana)

Behavioural laterality in nonhuman primates has been commonly studied in paired limb organs, and studies in unpaired organs such as tails are less common. The very limited investigations on tail laterality have focused on New World primates. We firstly investigated the lateral bias of tail wrapping in an Old World primate. From a wild group of one hundred of golden snub-nosed monkeys (Rhinopithecus roxellana), 14 adult monkeys, 7 males and 7 females, were chosen as focus animals. The data of tail wrapping in two different postures that were resting on the ground and climbing the tree trunk were collected and analyzed. The results demonstrated (1) that, when resting on the ground, the focus animals, 3 showed right-side tail-wrapping preference and 11 were ambipreferent; (2) that there was a population-level right tail-wrapping preference in climbing, and 9 of them showed right-side preference, 1 left-side preference and 4 were ambipreferent; (3) and that there were no significant sex differences on the direction and strength of tail wrapping laterality. These findings provide significant evidence for a difference of cerebral asymmetries in tail-wrapping control and would be valuable for further understanding the important function of tails in Old World primates.