The Nutritional Basis for Food Selection by Ungulates

Abstract

A conceptual framework is outlined for understanding the reasons why ungulates select the kinds of foods that they do. It consists of four morphological parameters: (1) body size and (2) type of digestive system (cecal or ruminant) determine the overall time-energy constraints within which the ungulate may forage selectively; (3) rumino-reticular volume to body weight ratio determines the type of food the ruminant is most efficient in processing; and (4) mouth size determines the ability of the ungulate to harvest selectively plant parts of individuals. Principal premises are the following: (1) large ungulates and cecal digestors are more limited by time than are small ungulates and ruminant digestors; (2) high rumino-reticular volume to body weight ratio is an adaptation to exploiting thick cell-walled, high cellulose diets (i.e., graminoids); and (3) low rumino-reticular volume to body weight ratio is an adaptation to exploiting thin but lignified cell-walled diets (i.e., browse).