Ware the Falling Bison?

There's a national park an hour from our house and we finally got around to going up there.  Why is it you can never find time to go see things near home that others drive hundreds of miles to see?  Anywho, I was rather appalled at the lack of a certain type of warning sign.  There were the commonplace: 'don't feed the prairie dogs, watch for falling rocks, and don't get trampled by bison,' signs, but there was certainly a dearth of vitally needed signage.  The park was gorgeous and well worth the visit, all hills, cliffs, and deep gullies.  The problem was that the ubiquitous bison like to perch precariously on said cliffs, often over the road, while trying to reach a certain desired bit of greenery.  Forget the rocks, watch for falling bison!  In this world where every plastic bag must be labeled as deadly to children, I thought this oversight rather amusing, not that said buffalo have likely ever fallen on anyone, but it was rather impressive looking straight up and seeing a buffalo grazing twenty feet overhead.