How Fox Squirrels Influence the Invasion of Prairies by Nut-Bearing Trees

Abstract

The purpose of this study was to gain information on how squirrels respond to nuts buried on prairie-forest ecotones as a means of understanding how squirrels influence the invasions of prairies by nut-bearing trees. Of the three common species of nut-bearing riparian forest trees studied, seedlings of black walnut, Juglans nigra , the species whose nuts are most highly preferred by fox squirrels, Sciurus niger , tended to occur farthest from the forest edge onto the prairie. Squirrels removed walnuts buried in the woods in direct proportion to the density of the nuts buried, rather than in proportion to the distance the nuts were located from a conspecific nut-bearing tree. In contrast, when walnuts were experimentally buried at extremely high densities in prairies next to woods during a good mast year, squirrels removed those nuts more quickly that were nearer to the forest and did not remove nuts buried farther than 9 m from the edge of the canopy. Because walnut seedlings were observed at much greater distances from the forest edge, we speculate that squirrels may bury nuts on open prairies at considerable distances from forest cover in poor mast years, when the benefit of fewer nuts lost to other squirrels outweighs the added risk of predation in the prairie.