Although some mammalian generalist herbivores avoid foods high in plant sec
ondary compounds, it has not been adequately shown that eastern grey squirr
els (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 free-ranging grey squirrels with four types of dough balls that
differed in tannin and protein content. Squirrels consistently preferred lo
w to high tannin foods but did not distinguish between low and high protein
foods. Intensity of preference for low tannin foods was greatest during ea
rly 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, physiolog
ical competence, and nutrient complementarity may explain why squirrels con
sume tannin in natural diets, in spite of preference for low tannin dough b
alls demonstrated here.