Substrate Diameter and Orientation in the Context of Food Type in the Gray Mouse Lemur, Microcebus murinus: Implications for the Origins of Grasping in Primates Séverine Toussaint 1,2 & Anthony Herrel 1,3 & Callum F. Ross 4 & Fabienne Aujard 1 & Emmanuelle Pouydebat 1 Received: 24 February 2015 /Accepted: 29 April 2015 /Published online: 24 May 2015 # Springer Science+Business Media New York 2015 Abstract Grasping is a widespread behavior among tetrapod vertebrates. In primates, the hands and feet are involved in many tasks including arboreal locomotion and food acquisition. Yet, the origin and the evolution of prehensile capacities, which are highly diversified across this group, remain open for inquiry. Some researchers suggest that grasping evolved in an arboreal habitat consisting of fine branches associated with insect predation and/or fruit and flower exploitation. However, few studies have tested the importance of arboreal conditions and diet, e.g., frugivorous, omnivorous, on the use of the hands in food grasping. The aim of this study was to link substrate use and food grasping strategies quantitatively to test hypotheses concerning primate grasping origins. We studied a species often described as a good ecological model to study the origin of grasping in primates, Microcebus murinus, and quantified its spontaneous substrate use (diameter and orientation) in an unconstrained environment while pre- senting them with different food types (static and mobile). We show that 1) Microcebus murinus appears to be an opportunistic rather than a specialist user of fine branches as suggested previously, at least under laboratory conditions; and 2) food properties had an impact on the use of the hands vs. the mouth, with the hands being used more for the Int J Primatol (2015) 36:583–604 DOI 10.1007/s10764-015-9844-2 * Séverine Toussaint severine.toussaint@mnhn.fr 1 Département d’Ecologie et de Gestion de la Biodiversité, UMR 7179, C.N.R.S/M.N.H.N., 75231 Paris Cedex 05, France 2 Département Histoire de la Terre, Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements, UMR 7207 C.N.R.S/M.N.H.N/U.P.M.C., 75231 Paris Cedex 05, France 3 Evolutionary Morphology of Vertebrates, Ghent University, B-9000 Gent, Belgium 4 Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois 60637, USA