Mammalian chewing rate scales inversely to body mass (M); however, controversy exists over the value of the scaling exponent. Different mechanisms explain different values of the scaling exponent; hence, a better estimate of the exponent would provide insight into the mechanisms governing chewing rate across mammalian species. We evaluated the relationship between mean chewing cycle duration (CD; i.e., the inverse of mean chewing rate) and M in 132 species and removed phylogenetic effects by using an independent contrast method currently used in evolutionary biology studies. A one-third–power law resulted when independent contrasts were not used; however, a one-third– to one-fourth–power law resulted when independent contrasts were used to remove phylogenetic effects. We hypothesize that variation in the scaling exponent is due to natural selection acting to increase metabolic efficiency; and variation in the complexity of mandibular kinematics, motor control asymmetry, and mandibular biomechanics, which may act to increase CDs above the “ideal” one-fourth–power law. Future studies should consider effects due to jaw-movement kinematics, motor control issues, and biomechanics.