White bison are extremely rare. Only about one in ten million bison born are white. They can be white for several reasons. In this case, the one I have depicted is leucistic, that is, lacking all pigment, hence it has blue eyes.
The occurrence of a white buffalo is said to be a sacred sign in several Native American religions, including the Sioux and Lakota, where the birth of a white calf is a sign of prosperity. The stories I found only mentioned white calves. I saw no reference to adult wild white bison. There is however a movie called The White Buffalo. It starred Charles Bronson and was a kind of western-horror hybrid. I saw it when I was a kid and remember it being pretty scary.
I used Poser 6 to pose the bison, and then imported it into Vue 9.5 where I constructed the rest of the scene. Final rendering was done in Vue and took about 8 hours on an Intel I5 2.8 GHz with 8GB of ram. For post-production, I used GIMP where I got to try out my new Wacom Bamboo tablet.
Prints for this are available from my website here: [link]