The effects of tannin and protein on food preference in eastern grey squirrels

Abstract

Although some mammalian generalist herbivores avoid foods high in plant secondary compounds, it has not been adequately shown that eastern grey squirrels (Sciurus carolinensis), who regularly encounter tannin in acorns, avoid high tannin diets. Dietary tannin can inhibit nitrogen assimilation; hence herbivores that eat tannin should seek high protein diets to compensate. I presented freeranging grey squirrels with four types of dough balls that differed in tannin and protein content. Squirrels consistently preferred low to high tannin foods but did not distinguish between low and high protein foods. Intensity of preference for low tannin foods was greatest during early to mid autumn, when food is relatively abundant, and declined into the spring and early summer, when food is relatively scarce. Food availability, partitioning foraging effort between eating and scatterhoarding, physiological competence, and nutrient complementarity may explain why squirrels consume tannin in natural diets, in spite of preference for low tannin dough balls demonstrated here.