The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Mandibular bone stiffness in sooty mangabeys


1Anthropology, University of Florida, 2Anthropology, The Ohio State University

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Field research has established that mangabeys representing both Lophocebus and Cercocebus are adept at orally processing hard objects either seasonally or year-round. This feeding strategy is reasonably inferred to involve intense masticatory loads during ingestion. Much comparative investigation of skeletal responses to hard-object feeding has also focused on craniofacial morphometrics, such that the structural properties of mangabey mandibles are interpreted in the context of diet and feeding behavior.

By contrast, little is known of the material properties of mandibular bone as they relate to hard-object feeding in primates. In this study, we investigate bone stiffness in the postcanine corpus of four adult sooty mangabeys (Cercocebus atys). Hardness data were collected on coronal sections taken below M1 via Vickers microindentation and converted to elastic modulus through empirically-derived regression. Our sample represents a population from the Taï Forest, Côte d’Ivoire, in which the most frequently consumed foods are the very hard (i.e., stress-limited) seed casings of Sacoglottis gabonensis.

Elastic modulus averages 18.5 GPa within the sample. Sooty mangabeys show significant variation in bone stiffness among individuals, with significant differences between alveolar and basal regions. Nevertheless, Cercocebus atys is shown to have significantly stiffer mandibular bone than that of sympatric colobine monkeys. While this finding invites speculation that the material response to durophagy involves stiffening of bone tissue, other data collected to date – albeit limited – suggest that cercopthecines as a group have stiffer bone than colobines, irrespective of the incidence of hard foods in the diet.

Supported by NSF BCS-0922429 and 0921770.

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