The rate of food intake exerts an important influence on many aspects
of herbivore ecology, including diet and habitat choices, social organ
ization, and predator avoidance. When food is spatially concentrated,
short-term dry matter intake rate (I, g/min) is determined largely by
morphology of the mouth and mechanics of food consumption. Morphology
(tooth size and jaw musculature) and mechanics (cropping and chewing p
rocesses) are hypothesized to scale with body mass (M) for mammalian h
erbivores. By using a simple model of processes regulating short-term
I, we developed and tested hypotheses on the scaling of these paramete
rs in 12 species of mammalian herbivores whose masses ranged from 0.05
kg to 547 kg. Specifically, this model predicts that I is controlled
by the size of bite taken, by the time required to crop a bite, and by
the rate at which food in the mouth can be processed. Maximum bite si
ze scaled with M0.72, whereas cropping time did not scale with body ma
ss and averaged 0.015 min/bite across species. Food processing in the
mouth scaled with M0.70. We concluded that the maximum intake rate of
mammalian herbivores will scale closely with M0.71. This conclusion wa
s corroborated by 39 published observations of the maximum I of mammal
ian herbivores. Thus, the scaling of I coincides closely with the scal
ing of daily energy requirements.