Charles Krebs and colleagues applied three different treatments to populations to snowshoe hares: control (1), add fertilizer to increase growth of food plants (3), keep out mammalian predators by electric fences (2), and keep out predators together with added fertilizer (11). The numbers in parentheses represent the resultant numbers of hares relative to control numbers. What can you conclude?
A) Top-down control is most important B) Bottom-up control is most important C) Food limitation is important, but only after predator removal D) Predation by hawks and owls is important