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. Which one of the following, if true, most helps to resolve the apparent paradox? ['Insect parasites, such as certain species of ticks, that feed primarily on mule deer often dwell in trees, from which they drop onto passing deer.', 'Mule deer have enzyme-rich saliva and specialized digestive organs that enable the deer to digest tough plants inedible to other deer species.', 'Mule deer herds that inhabit cleared forests tend to have more females with young offspring and fewer adult males than do other mule deer populations.', "As plants receive more sunlight, they produce higher amounts of tannins, compounds that inhibit digestion of the plants' proteins."]