Food habits and nutrition of black bears during a gypsy moth infestation

Abstract

During 1988–1991 we determined food habits and indices of diet quality for a black bear (Ursus americanus) population in Shenandoah National Park, Virginia, experiencing a severe gypsy moth (Lymantria dispar) defoliation event, and compared the results with data collected prior to defoliation (1982–1984). Gypsy moth infestation resulted in extensive summer overstory canopy loss and a complete acorn failure in affected areas. As in predefoliation years, analysis of scats collected during defoliation indicated that bears ate primarily herbaceous vegetation in spring, followed by squawroot (Canopholis americana) and fruits of black and sweet cherry (Prunus serotina and P. avium) in summer. However, in early and late fall bears switched from consuming predominantly acorns before defoliation to pokeweed (Phytolacca americana) berries and grapes (Vitis spp.), respectively, during defoliation. Despite acorn loss, no decline in dietary nutritional quality was observed in comparisons of the percentages of crude protein, crude fat, and crude fiber in seasonal diets before and during defoliation. When it is available, bears can successfully exploit soft mast as a fall food source and do not necessarily experience a substantial reduction in food quality if acorn crops fail.