WASHINGTON, RL*; ECKHARDT, A; ROSS, CF; University of Chicago; University of Chicago; University of Chicago: Scaling of chewing frequency in primates

In mammals, significant food processing occurs in the oral cavity prior to swallowing, so ingestion rate is related to the rate of oral food processing. It therefore seems likely that chewing frequency is an important determinant of food ingestion rate in mammals. We investigated the determinants of chewing frequency (Cf) in anthropoid primates by examining the scaling of Cf against body mass (M). Cf was calculated from videos of zoo living primates ranging from 0.95 kg to 130 kg, and M was taken from zoo records and the literature. It has been hypothesized that Cf will scale similarly to other biological rates, i.e., as M^-0.25, or in a manner predicted by pendulum mechanics, i.e., as M^-0.17 (where jaw length reflects pendulum length, scaling to F^-0.5, and jaw length scales to M^0.33). It was found that Cf scaled to body mass in a manner compatible with the pendulum model, but in violation of the general biological rates model. This result was confirmed for chewing of different food types: food material properties varied in this study did not significantly affect chewing rate. This suggests that the size of the jaw may be the most important determinant of chewing rate in anthropoid primates.