One of the classic images of the Old West is that of the gnarled, grubby gold miner trudging through the creek-beds, canyons, and mountain passes with his trusty, heavy-laden donkey by his side. Miners didn't use horses because they were not sure footed enough to traverse the rough terrain, the narrow, winding trails, the slippery creek-side stones. After all, a successful miner had a donkey loaded with the most valuable cargo in the universe: gold dust and gold nuggets. Such treasure could only be trusted to donkeys.

Today tourists can relive some of the experience of donkey travel when they sign up to take the long trail ride down into the base of the Grand Canyon. I used to think that the donkey was used because his smaller feet and shorter legs made him more stable on the trail; or that…