In fact, the way that the herd moves is almost hypnotic - the herd is all strung out in a row in a way that recalls waiting at the tracks for a long train to cross. Or, to mix metaphors, watching them all in a row looks a little like an undulating snake. Or, let me offer one more. They look like a giant centipede, with a million tiny little legs moving it along at a nice trot.
Elk herds are often, but not always segregated by gender, with all of the males forming one herd and the females forming another. This herd does not appear to be all one gender or another, as there are clearly males visible, as well as females. Perhaps these folks have captured a gigantic group date in Bozeman, something akin to a singles mixer.
See the full video below, and comment if you've ever seen an elk herd cross the road!