Evolutionary History of food Withdraw Movements in Primates: Food Withdraw is Mediated by Nonvisual Strategies in 22 Species of Strepsirrhines

摘要

Abstract 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.