It has been suggested that strepsirrhines (lemurs, lorises, and galagos) retain the more primitive left hand preference, whilst monkeys and apes more regularly display a right hand preference at the individual-level. We looked to address questions of laterality in the slow loris (Nycticebus spp.) using spontaneous observations of seven wild individuals, unimanual tests in six captive individuals, and photos of 44 individuals in a bilateral posture assessing handedness at the individual- and group-level. During the unimanual reach task, we found at the individual-level, only four slow lorises showed a hand use bias (R: 3, L:1), Handedness index (HI) ranged from -0.57-1.00. In the wild unimanual grasp task we found at the individual-level two individual showed a right-hand bias, the HI ranged from -0.19-0.70. The bilateral venom pose showed a trend toward a right hand dominant grip in those photographed in captivity, but an ambiguous difference in wild individuals. There are many environmental constraints in captivity that wild animals do not face, thus data collected in wild settings are more representative of their natural state. The presence of right-handedness in these species suggest that there is a need to re-evaluate the evolution of handedness in primates.
Poindexter, Stephanie A.Reinhardt, Kathleen D.Nijman, VincentNekaris, K. A. I.
Faculty of Humanities and Social Sciences\Department of Social Sciences
Year of publication: 2018Date of RADAR deposit: 2018-03-23