Got a black lab that is absolutely worthless on ducks and he sometimes likes to start eating doves when he gets them. But,,, I can let him smell a bloody arrow and he will follow the trail to the deer. I didn't train him to do it, he just does it instinctively. Problem is, he won't stay with the deer after he finds it, he goes looking for something else to find but he will follow the trail to the deer so he is useful. I keep him in practice by letting him trail the deer even if I've already found it. Just take the dog out there and try him, you might be surprised.
"Suppose you were an idiot, and suppose you were a member of Congress, but I repeat myself." Mark Twain