The problem wit predators is they mostly are NOT specific in their approach. Alowing a predator population to increase may cause the over use of a prey animal that is not needed. as you cited about endangered species. We, as thinking predators can be selective in out take, as demonstrated by our game laws. We can take Black ducks one year ans if the population falls the balck duck season closes. We can still duck hun but focus on other more populated species. any other natural predator would be taking mallards, blacks, and others and does not have the ability to evaluate one against the other. That is the benefit I think we bring to the table over a natural predator.