La vidéo avec les bisons qui courent sur la route est un gros fake, ça se voit à 3 km.
D’ailleurs explications :

"Fake. CGI. The shadows from the buffalo are quite distinct. But the "orange posts" that are right next to the road, do not cast a shadow. Neither do any of the bushes. Some of which sit right next to the road.

Also, shadows are not one uniform value. The get darker toward the solid parts (or the "core") of the object and more "fuzzy" or less defined as the mass moves away from the surface the shadow is cast on. So, according the physics of light, the shadows near the hooves should be slightly darker and more defined. And the shadows of the bodies should be less crisp because there is more light bouncing around to lighten it.

UNLESS the sunlight is particularly bright. Which it is not. ?"

http://www.bison.tv/videos-yellowstone-bison-on-the-run-%5BRiexHmbJlp4%5D.cfm