I have been told that when Hannibal began his crossing of the Alps, he had something like 38 war elephants with him. However, once he made it to Italy, only a few were left. Have the remains of any of the elephants that did not survive the crossing been found?
This thread has some good information about it. Basically though, no one is really certain of the route that they took through the alps, which makes it difficult to choose where to look. And actually, any remains found of elephants would probably give a more definitive answer as to the route. Also, being in the Alps, it's hard to search for any possible remains in general, even if you have a good idea of where to look.
I also came across this work that was done on the subject at Stanford: Hannibal in the Alps: Stanford Alpine Archaeology Project 1994-2006. It talks more in depth about the search they did for any such remains, but again, the same issues are still present of not knowing where to look and difficulty searching in general.
I was literally just about to comment re: the Stanford archaeology project, which looks to be one of the main projects doing archaeological digs in the Alps with the purpose of finding artifacts tied to Hannibal's crossing.
I did find one other article which discusses the possible routes that seem to draw the most attention as candidates for the actual route used. It also gives a good overview of the historical sources (Polybius & Livy), but it's more geared toward a geologist's work on identifying the route, as he attempts to match up the geological/environmental identifiers mentioned in the sources with the most likely route across the Alps.
On Hannibal's Trail: The clues are in the geology | Earth Magazine
Great question though, and I'd be super interested if anyone else has something to add.