Maybe I missed something, but it seems to me that the article says they found horse dung on a bridle path, and therefore Hannibal took that route.
Wouldn’t one expect horse dung on a bridle path whether or not Hannibal had passed? How do they know it belongs to horses that belonged to Hannibal?
I wondered about that, too. The only thing I can think is that they found a LOT of the horse dung that carbon dated to the right time.