Seasonal changes in digestion in black bears

Abstract

The ability of bears (Ursus spp.) to accumulate fat reserves before winter denning is essential to winter survival and successful reproduction. We conducted an experiment to determine if the digestive ability of black bears (U. americanus) changes seasonally. Six captive bears were fed commercial dog food rations and the digestibilities of gross energy and crude protein were determined in August and again in November. Bears showed significantly higher digestion of gross energy and significantly lower digestion of crude protein in November than in August. We suggest that a systemically mediated increase in fat and carbohydrate assimilation, at the expense of protein assimilation, occurs in the fall, and that this is an adaptation facilitating rapid weight gain before denning.