Foraging behavior of the southern flying squirrel was studied under conditions of declining photoperiod and temperature. Experiments tested predictions derived from a theoretical model suggesting hickory (Carya spp.) nuts as the optimal food for flying squirrels at temperatures below −10 C. Above this temperature flying squirrels could meet their daily energy needs more quickly on a diet of acorns. During a declining photoperiod and mild temperatures flying squirrels stored hickory nuts whereas acorns were usually eaten at the site of discovery. Test animals foraging at low temperatures significantly increased the number of hickory nuts consumed and decreased the number of acorns consumed. By eating acorns in the autumn and storing hickory nuts for winter consumption flying squirrels make use of a dynamic foraging strategy that allows optimal use of both autumn and winter food resources.