Two cowboys on horseback get into a hot pursuit as the gate opens and the bull charges into the arena.
One flanks him, the other tries to grab him by the tail to drag him at a gallop and pull him to the ground.
This is coleo, a Latin American twist on rodeo that has drawn cowboys from around the region together in Colombia for the world championships from October 10 to 13.
Wearing cowboy hats or protective helmets, nearly 200 "coleadores" take turns in the arena, dragging young bulls that weigh around 400 kilograms (880 pounds) until they fall to the dusty ground.
The animals often roll several times before coming to a stop and getting up in a daze as the cowboys move in for the next round.
Animal rights activists condemn it as cruel. To fans, it is at once sport, art and tradition.
"It's one of the most beautiful sports, even though it's dangerous," said Gustavo Vargas, a 26-year-old blacksmith with the silhouette of a horse's head shaved into his hair.
"It means a lot to me because I was born on the plains," said 61-year-old Colombian cowboy Angel Zambrano, a four-time world champion who has watched the competitions grow up from informal street events to highly organized contests with their own long, rectangular arenas.
Both cowboys were competing to take home the $20,000 first prize at the 18th world championships in Villavicencio, about an hour's drive southeast of Bogota.
In all, about 160 Colombians were competing, along with a dozen other cowboys from Costa Rica, Cuba, Mexico, Panama and Venezuela -- all of them men.
As fans bought beer and barbecue in between rides, the voice of Latin Grammy winner Orlando "Cholo" Valderrama belted out from the arena's loudspeakers.
"I'm a coleador from the village and I don't deny it, my greatest pride is bringing down a raging bull. The blood of the grandfathers who forged these plains gallops in my veins," sings the Colombian folk star.
- Culture or cruelty? -
The championships have become a tourist attraction since they began in 1997.
But not everyone is a fan.
"Coleo is an abusive sport, singular for its cruelty and its indifference to pain. If we put ourselves in the bull's place, we'd understand that we should have abolished these events long ago," Latin American activist group Anima Naturalis says on its website.
"We've had some difficulties with animal rights activists, who don't share in this activity because they think it's animal abuse," said Julio Eduardo Santos, the tournament's founder.
Veterinarian Andres Valencia said the sport was less harmful than bullfighting.
"Here there are no lacerations with sharp objects, they're not trying to kill the animal," he told AFP.
"The worst thing the bull suffers is stress."
He said fractures were not common but did occur, and that the bulls were put down in such cases to end their suffering.
"It's a way of preserving what's ours," said 39-year-old rancher Henry Vaca of Colombia, as his seven-year-old son showed off his roping skills.
"It's a tradition that should be handed down through the generations," added Victor Yelamo, a Venezuelan lawyer who said he had been practising coleo since he was five years old.