This is Bert, and Walt’s got her up on a pregnant mare in a corral belonging to his buddy Ray.
Bert does not like horses. In theory they are beautiful animals, but she doesn’t trust their girth and flight. In fact, an hour before this photo was taken, Walt and Bert and Dondi were riding horses in the Casper foothills when Bert’s horse took off with her, leaving Bert terrified and weightless as she clutched at the reins and pinched the saddle between her knees, swearing off riding forever.
But back in the corral, Walt urges her up on a different mare. “Nahhhhhhh,” is Walt’s reply to Bert’s more intellectual argument against horses.