If you visit Custer SP while in the area, drive the wildlife loop early morning or late afternoon. The wildlife in the park hide in the trees in the heat of the day. And its a state park, so the NP pass doesn't work. But it isn't expensive.
And take some carrots. Lots of wild burros in the park. In the gold rush days, miners that didn't hit the "mother lode" just turned their pack animals loose and moved on. Their descendants run quite a scam. One stops in the middle of the road to stop traffic and the others go from car to car begging for food. They have lousy eyesight, so use long carrots and hold them by the green part or you could lose a finger. :)