But even the bison, with its huge head and powerful neck and legs, can have problems when crossing the snow melt fed rivers of Yellowstone. We captured these bison crossing the Madison River on the west side of Yellowstone. This was most likely a bachelor heard, males who do not yet have a harem of females to attend.
At this time of the year mixed herds, herds consisting mainly of female and young with a dominant bull, often gather together into a large herds to help protect the young calves from predators, such as bears, wolves and coyote. It is often difficult for these large herds to cross rivers at this time of the year because the current is frequently too strong for the young to make it safely across. This is one reason why you often find the bison on the road in Yellowstone, because it is often the easiest path to travel.