We used cafeteria-style feeding trials with 8 types of mast in various comb
inations to examine differences in resource selection among 5 syntopic spec
ies of granivorous forest rodents in west-central Indiana. Patterns of reso
urce selection corresponded to differences in phylogeny and body size of gr
anivores, with greatest similarities among closely related species of simil
ar body size. Breadth of resource use varied inversely with body size in ou
r trials, Resource selection by Sciurus carolinensis, S. niger, and Tamiasc
iurus hudsonicus was correlated positively with caloric and lipid content o
f mast and its size, whereas selection by Glaucomys volans was correlated n
egatively with the percentage of protective tissue associated with seeds. L
aboratory trials indicated that T. hudsonicus and G. volans discriminate am
ong mast of comparable physical and chemical composition on the basis of si
ze, with a preference for larger seeds. Contrary to our expectations, T. hu
dsonicus, a recent immigrant from the boreal forest, did not exhibit a pref
erence for seeds of red pine (Pinus resinosa) relative to mast of hardwood
species. G. volans and Peromgscus leucopus tended to consume perishable whi
te oak acorns immediately and to cache a substantial portion of less perish
able seeds of nonpreferred species. Our results demonstrate the potential f
ur considerable overlap in resource use among members of this guild. Guild
members also seem to be affected differentially by physical and chemical pr
operties of mast, and patterns of resource selection reflect contrasting fo
raging constraints under which these animals operate.