Slow lorises (Nycticebusspp.) display evidence of handedness in the wild and in captivity

Abstract

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 7 wild individuals, unimanual tests in 6 captive individuals, and photos of 42 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 4 slow lorises showed a hand use bias (R: 3, L: 1), Handedness index (HI) ranged from -0.57 to 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 to 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 suggests that there is a need to re-evaluate the evolution of handedness in primates.

Venom in Furs: Facial Masks as Aposematic Signals in a Venomous Mammal

“…Their venom is produced through combining oil from a brachial gland with saliva from their mouth when the animal raises its arms over its head [22]. When threatened, the slow loris hangs bipedally with the arms folded above the head, meaning that the nuchal area is most likely presented to a combatant [23]. Their venom was initially proposed ultimately to have an anti-predator function [24].…”

Hand preferences and differences in extractive foraging in seven capuchin monkey species

“…In the last decades, studies evaluating hand preference in non‐human primates have increased greatly, both in captive and wild populations, and various authors suggested that a right hand bias at the population level does occur in non‐human primates (Hopkins et al, ; Humle & Matsuzawa, ; Llorente et al, ; Lonsdorf & Hopkins, ; Molesti, Vauclair, & Meguerditchian, ; Neufuss, Humle, Cremaschi, & Kivell, ; Poindexter, Reinhardt, Nijman, & Nekaris, in press; Regaiolli, Spiezio, & Hopkins, , 2018; Spinozzi, Castorina, & Truppa, ; Tabiowo & Forrester, ), but this right hand bias is not as strong and stable across different tasks as in humans (Cashmore, Uomini, & Chapelain, ; Marchant & McGrew, ). Other studies, however, with the same and different species report that lateralization in hand preference occurs only at an individual level (Brand et al, ; Leca, Gunst, & Huffman, ; Lilak & Phillips, ; Marchant & McGrew, ; Meunier & Vauclair, ; Papademetriou, Sheu, & Michel, ; Westergaard & Suomi, ).…”