Patterns of hand and mouth lateral biases in bamboo leaf shoot feeding and simple food reaching in the gentle lemur (Hapalemur griseus)



Lateralized feeding behaviors of 7 wild-born and 6 captive-born Hapalemur griseus sp. were evaluated in two conditions, simple food reaching and species-typical bamboo foraging. Gentle lemurs were found to have the strongest lateral hand preference in simple food reaching of any prosimian species yet studied. However in this small sample, population-level lateralization was not found: 5 preferred the right hand and 8 the left. The movement pattern used by hapalemurs when feeding on bamboo leaf shoots was categorized into four components: PULL IN, COUNTERFORCE, TURN, and FEED IN. Lateral hand bias was scored for all four components and lateral mouth preference was scored for the two components that involved the mouth (COUNTERFORCE and FEED IN). Strong positive correlations were found between hand preference in the most lateralized components of shoot eating (TURN and FEED IN) and simple food reaching. This suggests that the gentle lemurs' species-typical bamboo feeding behavior may contribute to the exceptionally strong hand preference for simple food reaching seen in this species. There were negative correlations between the component measure of shoot feeding that required strength (COUNTERFORCE) and the components that required manipulation (TURN and FEED IN). Within the COUNTERFORCE and FEED IN components, mouth preference and hand preference were positively associated in a manner that suggested one side of the mouth was preferred for removing the shoot and the other side for mastication. Asymmetrical dental wear may provide a means of dating behavioral lateralization in ancestral species. © 1993 Wiley-Liss, Inc.