Survival is a purpose, hunting is simply a possible means to that purpose. I feel that the only time hunting can be considered a purpose of a species' existence is if it is to maintain a balance in nature. Much like how the hunting by spiders keeps the fly population in balance.
On the other hand, since life was not consciously created one can't really say it has a purpose and that it is left to ourselves to find our own purpose. I imagine that there are some people who truly enjoy hunting and have made that as their personal purpose in life.