Usually a horse gives some warning that it is about to buck by dropping its head, slowing down or stopping, and excessively rounding up its back. With such an advance warning, riders can intervene in early stages by encouraging forward motion or circling.
Horses often signal an impending buck with a combination of physical cues: lowering their head, slowing down, and arching their backs. Riders can anticipate and mitigate this behavior by responding with appropriate interventions like encouraging forward motion or maneuvering around the horse.