Fox squirrels in Ohio prefer hickory nuts, acorns, corn, and black walnuts. The squirrels are absent where two or more of these mast trees are missing. In March, they feed mainly on buds and seeds of elm, maple, and willow. In Michigan, fox squirrels feed on a variety of foods throughout the year. Relatively few natural predators can regularly capture adult fox squirrels.
Habitat reduction is one cause.
One of the primary reasons for the decline of the endangered Delmarva fox squirrel is timber harvest. As large trees are removed so are much of the areas that provide the Delmarva fox squirrel with an open understory habitat. In addition, the effects of timber harvest prohibit fox squirrel habitat from developing. In cut-over areas where all den trees have been removed, den boxes can be used to supplement natural den trees.