Oak-rodent interactions create a complex selective environment for acorns given the dual role of rodents as seed dispersers and predators.Scatter-hoarding tree squirrels are keystone dispersers of the oaks but can also be devastating seed predators.We present evidence that oaks have adapted to this environment by producing acorns that serve as both a fruit for dispersal and an energy source and protection for the developing seedlings.We show that several oak species produce acorns with apical and basal halves that differ significantly: with basal halves providing a dispersal reward for rodents and the apical portion providing embryo protection.Chemical analyses of acorns across of three species (Quercus rubra,Q.palustris,Q.alba,n = 16-22 trees each) reveal higher lipid levels in the basal portion of the acorn and higher tannin levels in the apical portion.Sodium levels were also found to be higher in the basal half of Q.rubra acorns.Discriminant functions for all three species definitively classify apical versus basal sections of acorns using a variety of chemical attributes (jackknifed classification rates ranging from 79 to 91%) .In addition,simulation of acorn damage followed by greenhouse and field experiments demonstrate that acorns of five oak species tolerate significant damage and still establish.These results,coupled with the fact that five species of seed predators are known to selectively consume the basal portion of red oak acorns while leaving the apical end intact,suggest acorn structure is more intricately adapted for dispersal than previously thought.