Gray squirrels' faulty memories turn out to be good for forests, but the nut-hoarding habits of their red cousins are not, U.S. scientists said this week. The bane of suburban gardeners and backyard bird feeders, the ubiquitous gray squirrel buries walnuts, acorns and other nuts across the landscape in a pattern called "scatter hoarding," a Purdue University scientist said. Some nuts are forgotten and have a chance to germinate and sprout into black walnut, oak and hickory trees needed to regenerate steadily retreating hardwood forests.