Abstract
The rate at which a herbivore consumes food exerts an important influence on many aspects of its life, including its activity budget, diet and habitat choices, social organization, and predator avoidance. To obtain food, mammalian herbivores are obligated to spend time searching for and handling bites of vegetation. Therefore, short-term intake rate is determined largely by the mechanics of chewing, cropping, and locomotion, and the size and shape of the mouth, teeth, and legs. Using simple models of short-term intake rate and encounter rate, I developed and tested hypotheses on the scaling of these parameters with body mass (M) in 15 species of mammalian herbivores ranging from 0.05 to 547 kg. Maximum intake rate was a function of bite size, the rate at which food could be processed in the mouth, and cropping time. Maximum bite size scaled with M^0.72, whereas cropping time did not scale with body mass, averaging 0.015 min/bite across species. Food processing in the mouth scaled with M^0.70. Encounter rate, in turn, was a function of the distance between plants, the maximum sustainable travel velocity while foraging (V[max]), and the rate of acceleration and deceleration when leaving and approaching plants. V[max] scaled in proportion to M^0.05 and the rate of acceleration scaled with M^-0.17. The scaling of each of these parameters was generally predictable from mechanical processes and geometric similarity. Based on these relationships, I concluded that maximum intake rate of mammalian herbivores must scale reasonably closely with M^0.71. This conclusion was corroborated by published observations of maximum intake rate of 39 mammalian herbivores. Thus, the scaling of maximum intake rate coincides closely with the scaling of daily energy requirements. When the distance between plants is short (< 2 m), small animals will encounter plants faster and expend relatively less energy in foraging than do large animals. When distances are great, (> 2 m), the reverse is true. The scaling relationships for the model parameters were used to examine the interactions between animal size and the spatial characteristics of the plant community at scales ranging from leaflets to landscapes.
Shipley, Lisa Ann Shively (1993). The mechanics and scaling of intake rate in mammalian herbivores. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1531016.