title: The strategic role of the tail in maintaining balance while carrying a load bipedally in wild capuchins (Sapajus libidinosus): a pilot study.
abstract: The ability to carry objects has been considered an important selective pressure favoring the evolution of bipedal locomotion in early hominins. Comparable behaviors by extant primates have been studied very little, as few primates habitually carry objects bipedally. However, wild bearded capuchins living at Fazenda Boa Vista spontaneously and habitually transport stone tools by walking bipedally, allowing us to examine the characteristics of bipedal locomotion during object transport by a generalized primate. In this pilot study, we investigated the mechanical aspects of position and velocity of the center of mass, trunk inclination, and forelimb postures, and the torque of the forces applied on each anatomical segment in wild bearded capuchin monkeys during the transport of objects, with particular attention to the tail and its role in balancing the body. Our results indicate that body mass strongly affects the posture of transport and that capuchins are able to carry heavy loads bipedally with a bent-hip-bent-knee posture, thanks to the "strategic" use of their extendable tail; in fact, without this anatomical structure, constituting only 5 % of their body mass, they would be unable to transport the loads that they habitually carry.
authors.affiliation: Istituto di Scienze e Tecnologie della Cognizione, Consiglio Nazionale delle Ricerche, 00198, Rome, Italy. massaro.luciana@gmail.com.|Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, 00185, Rome, Italy. massaro.luciana@gmail.com.
authors.forename: Luciana
authors.initials: L
authors.lastname: Massaro
authors.affiliation: Istituto Nazionale di Fisica Nucleare, 00185, Rome, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Massa
authors.affiliation: Kinesiology Department, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Kathy
authors.initials: K
authors.lastname: Simpson
authors.affiliation: Psychology Department, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Fragaszy
authors.affiliation: Istituto di Scienze e Tecnologie della Cognizione, Consiglio Nazionale delle Ricerche, 00198, Rome, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Visalberghi
mesh_terms: D000818:Animals; D001938:Brazil; D002428:Cebus / Q000502:physiology*; D005260:Female; D008297:Male; D010865:Pilot Projects; D011187:Posture; D013623:Tail / Q000502:physiology; D053001:Tool Use Behavior; D016138:Walking
keywords: Bipedal locomotion; Center of mass; Tail use; Torque