People look at a large herd of bison with calves as the animals cross the road in the Lamar Valley, Yellowstone National Park, Wyoming, USA. The crossing caused traffic to back up on the road for about a half hour. Bison number about 5,500 in Yellowstone as of August 2016, according to the National Park Service. They are descended from a small group of 23 individuals that survived mass killings of bison in the 1800s.
{}