We document the use of goldenrod (Solidago spp.) gall insects by eastern gray squirrels (Sciurus carolinensis) as a winter food resource. We also examined the foraging patterns of gray squirrels on these gall insects by presenting goldenrod gall feeders at ten sites around Hamilton, New York, during the winters of 1996–1997 and 1997–1998. We predicted that squirrels would attack larger-than-average galls among those presented because larger galls are more likely to contain the larger fly larvae (Eurosta solidaginis), rather than the smaller parasitoid (Eurytoma gigantea) or nothing at all. Squirrels attacked galls at least once at 6 of the 10 sites where gall feeders were maintained. Galls at feeders were attacked from 11 February to 17 April, and the number of separate attacks on galls at a particular site ranged from 1 to 17. We detected no evidence that squirrels preferentially attacked galls of a particular size class (small, medium, large). There was no indication that squirrels attacked increasingly larger-than-average galls over the duration of the study, which would be expected if squirrels were learning by positive reinforcement. Our results suggest either (1) that squirrels are unable to discriminate among food rewards in galls of different sizes or (2) that all gall insects, regardless of size, provide an important dietary supplement for squirrels during the winter.
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Vol. 142 • No. 1