We had barely been in Yellowstone an hour when a small herd of bison walked right down the road right by the cars and then into the parking lot for one of the geysers. Then a ranger came by and said that they do this often! Later in the trip we saw bison in that same spot just strolling down along the highway.
This picture was taken at Mammoth Hot Springs just behind the Visitor's Center where a small herd was relaxing nearby in the green grass in the noonday heat. According to the North American Elk Breeders Association twinning is rare so I'm not sure these are twins or an example of adoption of a motherless calf. Calves are born in May or June and this photo was taken in early June.