Bulls are angered by the color red
Bulls do not respond specifically to red. Cattle are dichromatic and cannot perceive red as a distinct color. What triggers a bull's charge is movement, not the color of the object moving. The red cape in bullfighting serves a purpose for human spectators, not the animal.
What we know
The cultural association between red and bull aggression likely originates from the red muleta used in bullfighting. But cattle have dichromatic vision, meaning their retinas contain two types of cone cells rather than the three that allow humans to see red. As a result, bulls perceive red and green as similar, muted shades and cannot distinguish the color red from other colors in the same wavelength range.
A 2007 MythBusters investigation tested this systematically by placing red, white, and blue flags in a bull ring and found that the bulls charged all flags with equal ferocity, showing no preference for red. In a subsequent test, a stationary red object was ignored while a moving blue or white flag attracted charges. When a person dressed entirely in red stood motionless while matadors moved in other colors, the bull chased the moving figures and ignored the red-clad stationary person.
The driving stimulus for bull charging behavior is movement and the perceived threat of a moving object. In bullfights, the matador continuously moves the cape to provoke charges; the color is irrelevant to the bull. The red color traditionally used in bullfighting serves to hide bloodstains from the audience, not to anger the bull.
Bovine aggression is also influenced by past experiences, pain from picadors, confined spaces, and the general stress of the bullfighting environment. None of these factors are color-specific.
Common claims
- Bulls charge red objects specificallyFalse - they respond to movement
- Bulls can see red as a distinct colorFalse - they are dichromatic
- The red cape in bullfighting is to anger the bullFalse - it conceals blood from the audience