Hunting should be legel because:
1. Hunters want surplus large mammals.
2. Hunters fund both habitat and animal balance.
3. Humans can't do much to control wind, rain, snow, or temperature, all key factors in undulant reproduction but we can control human predation wherein we can manage against these uncontrollable elements in the environment by increasing harvest to prevent broad-spread starvation when herds over populate. Humans can harvest predators when undulate numbers are too low to produce a surplus. Humans can, through hunting, keep all mammals in the system in balance. Left to themselves nature large mammals will balance their numbers but they do it in decades and centuries rather than in a few years like humans can do through cognitive pressure points on specific species in specific locations.
4. In as much as humans can't leave the planet nor roll back our demand for acreage we are unable to allow large wild mammals free range, therefore if we simply leave these species to themselves the non-human predator species will over harvest the undulates. Eventually the predator numbers will drop back to a much smaller number because of the lack of wild undulates, ( assuming we could prevent them from eating our sheep, cows, horses, dogs and cats ) unlike human hunters predators do not have the cognitive ability to back off when they over hunt, they just kill by instinct (much like the dwr) and will kill the last of the herd without the knowledge that tomorrow they'll starve.
5. Because most humans, at least those that understand nature in any way, want to share our environment with as many species as possible. Hunters, above all, want wolves and bears and cougars as well as undulates (moose, elk, deer, caribou, etc.) Where hunters differ from non-hunters is hunters understand that there are locations where our environment can tolerate specific large predators and environments where it can not. We want them where conditions will tolerate them and we want to controlled them where our "civilized environment" can not tolerate them. Many years ago our grandparents had it pretty much figured it. Recent experiments with the wolf reintroduction in Idaho, Montana and Wyoming have proven what happens to the predator/prey balance when hunters are removed from the equation. Hunters believe and have proven over the last 100 years that we can have large amounts of all large mammals, in certain locations, (obviously we can't have large herds of moose and elk in down town Boise, Billings or Salt Lake (for obvious reasons) but we can have them in our less populated mountain and foothill ranges (for obvious reasons), and we can have large herds of moose and caribou and wolves in the sparsely populated areas of the north, which should once again should be clearly obvious but some pretend it's not, however it's political rather than logical.
6. Whether some accept it or not hunters can see the big picture and will manager for more of all species than non-hunters have interest or investment in having. Non-hunters want animals but they are generally uninvolved and unattached where as these animals, all of these animals are directly connected to hunters lives. Hunters are highly interactive with wild animals, up close and personal. We have elk, because of hunters, we have wild sheep, because of hunters, we,have mt. goats, because hunters want them, we have moose because of hunters, we ever whitetail deer, because of hunters, we have upland and migrator birds because of hunters. We have antelope because hunters want antelope. If we ever have mule deer again it will be because of hunters.
We protect them, fight for them, invest in them, and we worry about them, without legal hunting, pure and simple, we'll have FAR FEWER ANIMALS OF ALL SPECIES.
And all the reasons listed in the other posts.
DC