thats an entirely different argument involving the demographic structure of our population and cultures.
granted the animals think things through, they would not be causing a gamble in killing the second gazelle should they plan out the necessary facilities to preserve its potential!
keep in mind this is a very stretched topic, wherein these lions are both intelligent enough, and dexterous enough to perform menial tasks.
a pair of clothes are by no means the total potential use for the second gazelle. they could plan ahead and improve their quality of survival by storing and preserving food like a rainy day fund. (wouldnt it be rediculous if humans ate everything they harvest? then when a hurricane or the like came around and we lost the facilities to harvest, or the lions and their ability to hunt, then we would all starve.) whats more! they could fashion a waterskin, bone weapons, any number of potential uses!
BUT, all of this potential CAN be wasted. Do not confuse my argument with saying that people are fiscal in their use of goods. it is indeed true that many people unnecessarily waste things. this has nothing to do with humanity as a governing body, however, but with upbringing in the modern age. people of old establishments were much more cautious in their use of materials because it had a much larger impact on their lives. people now, however, do not have nearly the workload. we have automated factories and brilliantly efficient means of creating any number of things. however, this has the drawback wherein people forget exactly how dangerous life can be without these luxuries.
there is indeed improvement possible for us. humans have not yet even began to reach their potential. =] this is why i am open minded to supportings things like recycling and reuse. it serves the better purpose of devoting rarer and less readily recreated resources elsewhere.
so, yes, humans waste too much. if the lions did indeed have such a simple mindset as "gee, maybe we can use this", and then killed the gazelle without thinking through any actual uses, it would not be an intelligent action.
so the real dilemma is not whether humans should take from the environment or not--it is how we can do so effectively!