Sometimes it is necessary to cull a population of deer. Say that there is 50 deer on an island and food to sustain only 25, the result is depletion of food and slow starvation death. it sounds cruel but it is practical, when population of people grow it takes it's toll on animals, they lose out. The weak always suffer.
Hunting is a far more humane way to keep the animal population at a sustainable level. Right now in may area the raccoon population has exploded because few people hunt or trap them any more. To see those dying of mange and distemper isn't pretty.