DIGESTION-CONSTRAINED OPTIMAL FORAGING IN GENERALIST MAMMALIAN HERBIVORES

Optimal diet selection of generalist mammalian herbivores under the in fluence of a digestion constraint is analyzed using an algebraic model . The energy assimilation rate and the digesta mass are first formulat ed based on an assumed intake process from multiple food types differi ng in digestible energy content and digestive turnover time. The optim al diet is then analyzed under the assumption that animals maximize en ergy assimilation under the constraint of digestive capacity. The anal ysis suggests that diet preference is changeable according to the inte nsity of the digestion constraint. With a better intake condition (lon ger foraging time or more abundant food), the digestion constraint is intensified and diet selection is more oriented towards the digestive process: diet is composed of a smaller number of food types of higher digestive quality (digestible energy content per gross intake per dige stive turnover time). In contrast, with a loose digestion constraint, diet selection is more oriented towards the intake process: diet is co mposed of a larger number of food types of higher handling rate (diges tible energy content per handling time). Because diet preference is th us changeable, a priori ranking of food types is not justified in dige stion constrained herbivore foraging.