When old-growth forests are cleared of tall trees, more sunlight reaches the forest floor  This results in a sharp increase in the population of leafy shrubs on which the mule deer depend for food
Yet mule deer herds that inhabit cleared forests are less well-nourished than are herds living in old-growth forests
As plants receive more sunlight, they produce higher amounts of tannins, compounds that inhibit digestion of the plants' proteins.