I was fishing the Firehole at Biscuit Basin in mid-June working my way down stream and taking a bunch of trout in the trough at the far bank when a cow elk crashed into the river just below me. She forded the river and tried to exit on the far bank but kept failing as the water was too deep so she kept drifting down stream to a place where she could climb out. The cow fouled my honey hole but it was worth it to observe that moment.
I've seen big bull elk (they are surprisingly huge) grazing between tents at Madison campground and it astonishes me that people will get right up close to take a picture. If one of them took off running the camper would be flattened like a pancake and possibly mangled by those antlers.