This stumbled on to an interesting point, that I hadn't previously thought much about. I suspect elk will migrate when their herd size (or weather) causes the need to seek new feeding ground. If there not pushed to find food, I suspect they don't move. While lots of elk migrate, elk in some regions do not.
In regions where elk migrate they will do it with regularity that would do a salmon proud like others have said above. However I assumed that these paths were more about working directions of least resistance (between two or more historically good feeding areas) as opposed to an ingrained need in the elks brain to see specific landmarks and go the exact same path year after year.
That is why I was shocked to see the suggestion that the elk drowning was a result of the elk being "hardwired" to hold a straight and narrow path. The fact that some elk do not migrate suggests, to me at least, that they only require general directions, not a hard and fast path (like bees between a hive and a food source).
Presumably some elk know to go around, otherwise this group would have all died some years ago in one mass event. Although, perhaps I'm giving them too much credit considering the species at large can be fooled by decoys. (Of course select groups of hunters can't either for that matter).
Where these elk are going into the abyss, is it a huge wide opening on to the lake where it would take a few miles to go around or are we talking about a cove or corner of the lake, where a detour is not that much out of the way?