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Anthropoid vision contributes not only to reaching and grasping but also to the orienting of a food item during the withdraw movement to precisely place it in the mouth for eating. The evolutionary history of this visual control of feeding is not known. It likely evolved from the nonvisual control of the hand that is used with good effect for eating in many non-primate animal species. Strepsirrhines are a relatively large monophyletic group, diverging near the base of the primate cladogram, and described as using vision to reach for food. It is not known whether they use vision to orient food items during the withdraw movement. Video recordings of 7,464 withdraw movements from 22 species of captive strepsirrhines eating their normal food provisions were used to assess whether and how vision contributes to the withdraw movement. The constituent acts of withdraw movements, head orientation, body posture, ground-withdraw and inhand-withdraw, were assessed using frame-by-frame video inspection. Strepsirrhines were versatile in using their hands to get food to the mouth. They displayed variation between and within families that were weakly related to phylogenetic relationships and mainly related to feeding niches. There was no evidence that any species used vision to assist with the withdraw movement. Instead strepsirrhines used mouth reaching to take food from the hand and/or perioral contact to positioning food for biting. Our findings support two hypotheses: that visual mediation of food orienting for placement in the mouth during the withdraw movement is an anthropoid innovation, and that the evolution of the visual control of feeding was not a singular event.

The evolution of visual control of the hand to assist feeding by primates is uncertain but in anthropoid primates vision contributes not only to reaching for food and grasping it but also to the withdraw movement that brings food to the mouth. The strepsirrhines are a relatively large monophyletic group of Euarchontoglires near the base of the primate cladogram that are described as using vision to reach for food, but it is not known whether they use vision to assist the withdraw movement. The present study answere this question in 22 species of captive strepsirrhines from 6 of the seven strepsirrhine families, Daubentoniidae, Cheirogaleidae, Indriidae, Lemuridae, Lorisidae and Galagidae. Animals were videorecorded as they ate their normal food provisions. Dependent measures for analyses were ground withdraw movements, bringing grasped food to the mouth, and inhand withdraw movements, brining food held in the hand to the mouth, as well as the posture and head movements associated with each type of withdraw. Frame-by-frame scores from the video record showed that there were large differences between and within strepsirrhine families in these movements. Nevertheless, for all species, the withdraw movement was mediated by somatosensation, with mouth reaching and perioral contact with food determining how food was eventually eaten. Nonvisual behavior also contributed to food grasping as many species sniffed food before or during grasping. Even amongst species that made most use of the hand for their withdraws, the insectivoresLoris lydekkerianusandGalago senegalensis, and herbivores,Hapalemur simusandEulemur flavifrons, perioral contact was used to orient food for biting. The use of somatosensation and the absence of vision in mediating getting food in strepsirrhines suggests that visual mediation of the withdraw is an anthropoid innovation.