Ann Roy of Okawa asks :-
Why do bulls charge at red objects?
Kevin Stafford, a veterinarian at Massey University, responded.
Humans have very good colour vision and we probably appreciate a wider range of colours than most other mammals. In the human eye the retina which collects what we see has a large number of cones which are responsible for colour vision. The retina at the back of the eye in cattle also contains cones and there is good scientific evidence to show that cattle can discriminate between colours. It has been shown in a series of experiments that cattle can distinguish between colours. Cattle may find it easier to distinguish between colours with long wavelengths such as yellow, orange and red than between blue, grey and green.
Spanish fighting cattle have been bred for their ability to see and to respond quickly and they may be particularly capable of detecting the red capes used by bullfighters to attract their attention. The bulls see the moving red cloths and are stimulated to charge. It is probably a combination of colour and movement which triggers the charge as when the bullfighter holds the cloth still the bull may not charge. The suits worn by bullfighters are usually green or blue and may make the human a less obvious target than a moving red cloth to the bull. In Spain bulls only fight one time as they quickly learn to stop looking at the red cloth and than chase and attack the bullfighter.
Aggressive bulls of any breed will charge at any moving object when defending a territory or acting in self defense. Colour does not seem to be so important.