With the whole, "if I see another animal killing another, I'd leave it alone and let nature take it's course..." I would only do that in certain situations. If I see a cat in the process of killing a bird, I'll stop that cat and help the bird. I don't think I'd ever see a lion killing an antelope, but of course I couldn't stop that, nor would I want to. *That's* when nature is taking it's course.... not a bird/cat, dog/cat and so on.

Anyway, I'd help any and every animal, regardless of what it may be. (You know what I mean, hopefully.)