Buffalo herd
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Riding with the king of the buffalo round-up

In the Black Hills of South Dakota, 71,000 acres of dramatic terrain make up Custer State Park, home to antelope, mountain goats, bighorn sheep, deer, elk and most famously buffalo, also known as the American bison.

Every year, thousands of people turn out to watch cowboys and cowgirls as they round up and drive the herd of more than 1,000 bison.

It is a spectacular sight, as well as critical in maintaining a strong and healthy stock of animals.

BBC News met Chad Kremer, head of the herd, king of the round-up, and a good, old-fashioned cowboy.

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