AURORA, Colo. — Kaden Bustamante tottered out of the rodeo arena after the brief, rough ride he had endured on a careening mount landed him face down in the dirt. He spit dust from his mouth and tried to stanch the blood that had begun to pour from his nose.

Then he wailed for his mother. Kaden is 3; this was his first time riding a galloping sheep.

Mutton busting, as the sport is known, is the pint-size equivalent of competitive bull riding. Children cling to the backs of sheep, and generally speaking, whoever stays on the longest wins. But just as in bull and bronco riding, even the most talented rider ends up on the arena floor.

Playing make-believe rodeo with sheep has long been a pastime of rambunctious rural children. But the sport has begun to move from horseplay, and the occasional rodeo halftime show, to wider, sometimes suburban, audiences and competitors, toward becoming a codified sport with its own gear and championships.

Kaden was among the 20 or so children, most 3 to 6 years old, who competed during a mutton-busting event put on by Wool Riders Only at the Arapahoe County Fair here in Aurora, a suburb of Denver. Wool Riders Only is the sheep-riding affiliate of a company, Tommy G. Productions, that produces events like bull riding competitions and demolition derbies.