Scaling of chew cycle duration in primates
Article first published online: 25 JUL 2008
Copyright © 2008 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 138, Issue 1, pages 30–44, January 2009
How to Cite
Ross, C. F., Reed, D. A., Washington, R. L., Eckhardt, A., Anapol, F. and Shahnoor, N. (2009), Scaling of chew cycle duration in primates. Am. J. Phys. Anthropol., 138: 30–44. doi: 10.1002/ajpa.20895
- Issue published online: 1 DEC 2008
- Article first published online: 25 JUL 2008
- Manuscript Accepted: 3 JUN 2008
- Manuscript Received: 16 JAN 2008
- Research Experience for Undergraduates Supplement from NSF Physical Anthropology
- NSF Physical Anthropology. Grant Numbers: 97006676, BCS-010913
The biomechanical determinants of the scaling of chew cycle duration are important components of models of primate feeding systems at all levels, from the neuromechanical to the ecological. Chew cycle durations were estimated in 35 species of primates and analyzed in conjunction with data on morphological variables of the feeding system estimating moment of inertia of the mandible and force production capacity of the chewing muscles. Data on scaling of primate chew cycle duration were compared with the predictions of simple pendulum and forced mass–spring system models of the feeding system. The gravity-driven pendulum model best predicts the observed cycle duration scaling but isrejected as biomechanically unrealistic. The forced mass–spring model predicts larger increases in chew cycle duration with size than observed, but provides reasonable predictions of cycle duration scaling. We hypothesize that intrinsic properties of the muscles predict spring-like behavior of the jaw elevator muscles during opening and fast close phases of the jaw cycle and that modulation of stiffness by the central nervous system leads to spring-like properties during the slow close/power stroke phase. Strepsirrhines show no predictable relationship between chew cycle duration and jaw length. Anthropoids have longer chew cycle durations than nonprimate mammals with similar mandible lengths, possibly due to their enlarged symphyses, which increase the moment of inertia of the mandible. Deviations from general scaling trends suggest that both scaling of the jaw muscles and the inertial properties of the mandible are important in determining the scaling of chew cycle duration in primates. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc.