A bison like this one charged author and wildlife photographer Keith Sutton. The burly bull took out Sutton's tripod and camera. But Sutton scrambled to the top of his pickup, and safety. Photo by Keith Sutton.

For two weeks, my 16-year-old son Josh and I had traveled through the Great Plains. Much of our time was devoted to wildlife photography.

At Desoto National Wildlife Refuge in Iowa, we snapped shots of raptors, warblers and other interesting birds. North Dakota's Long Lake NWR gave us a chance to photograph sharp-tailed grouse, pheasants and jackrabbits. In the Badlands of South Dakota, we got up-close views of prairie dogs, bighorn sheep and pronghorns.

The one animal I was most eager to photograph, however, proved elusive. I wanted to capture some good images of wild American bison. But these great shaggy beasts were always out of range. We saw dozens, but none close enough to photograph.

Heading back home, as we crossed the South Dakota-Nebraska state line, I saw a sign for another wildlife refuge: Fort Niobrara.

This one wasn't on our itinerary, but I decided to detour through it anyway; I was road-weary, and an hour or two of wildlife watching would be a welcome respite.

Fort Niobrara is 19,131 acres of wildlife habitat along the Niobrara River in north-central Nebraska. The ranger at the visitor center said we could drive the 3 1/2-mile, self-guided tour route and expect to see a wide variety of birds, mule deer, elk, prairie dogs -- and bison!

I hadn't expected to find more bison on our trip home, and was thrilled that I'd get another chance to photograph these massive beasts.

Best of all, we arrived during rutting season. The big adult bulls, aloof most of the year, drifted among the groups of cows and calves.

The ranger said it would be easy to approach them in a vehicle, and that we were likely to hear the bulls bellowing as they pawed the earth, chased each other and fought.

Using a map, the ranger showed me where he'd last seen one of the refuge's biggest bulls. An hour later, Josh and I found the huge animal tending a group of cows and calves. We drove within 100 yards of the herd. To my great pleasure, they acted as tame as Holsteins at a milking barn as the bison shuffled along an old hogwire fence.

That fence, however, presented a problem. The bison weren't in an enclosure, but photos with hogwire in the background would make it look that way. I decided to leave the truck and approach the animals so I could zoom in with a telephoto lens and exclude the fence from my images.

Wary at first, I instructed Josh to keep the truck running just in case we had to make a quick getaway. But my fears seemed unfounded. The bison paid me no heed.