Bulls are known for charging at the red capes of matadors, but can they actually see the color red? Or are they colorblind like some other animals? Understanding bull vision and what colors they can perceive is an interesting scientific and biological question.
If you’re short on time, here’s a quick answer: Bulls are dichromats, meaning they have two color photoreceptors and can see some colors like blues, greens, and yellows but not reds. They likely rely more on movement than color when charging matador capes.
In this approximately 3000 word guide, we’ll take an in-depth look at bovine vision and visual perception. We’ll cover the structure and physiology of bovine eyes, how many photoreceptors cattle have, the limits of their color vision, how bulls detect motion, and more.
Anatomy and Physiology of Bovine Eyes
Structure of the Bovine Eye
The eyes of cattle have a similar anatomical structure to human eyes, but some key differences exist. The bovine eyeball is larger and more elongated. A tough white outer layer called the sclera surrounds the eyeball, helping to maintain its round shape.
At the front is the transparent cornea which overlays the iris and pupil. The iris controls how much light enters through the central pupil. Behind this lies the lens, which focuses light onto the retina at the back of the eyeball.
The retina contains photoreceptors called rods and cones that detect light and send signals to the brain via the optic nerve.
A few unique structures in cattle eyes aid their vision. Cattle have a reflective tissue called the tapetum lucidum behind the retina, allowing light to pass through the retina twice for superior night vision.
They also have a third eyelid called a nictitating membrane that can sweep horizontally across the eye to protect it from debris and dryness.
Retina and Photoreceptors
The retina lines the back two-thirds of the bovine eyeball and contains the photoreceptive rods and cones that absorb light and transmit signals to the brain. The central area of the retina called the fovea has a high density of cones for detecting color and details.
However, cattle have a streak-like area instead of a centralized fovea, giving them panoramic vision along the horizon.[1]
Rods outnumber cones in cattle eyes by a ratio of about 100:1. Rods function in dim light and detect shades of gray. The abundance of rods gives cattle excellent night vision. Cones function in bright light and detect color.
Cattle have two types of cone photoreceptors, allowing dichromatic color vision. They can distinguish blue and green wavelengths, but have limited perception of red hues.
Visual Pathway to the Brain
After light stimulates the retina, signals travel via the optic nerve to two brain structures. The main pathway is to the superior colliculus, which mediates eye movement and spatial orientation. A secondary pathway leads to the suprachiasmatic nucleus, which regulates circadian rhythms.[2]
Cattle have wide field of view, ranging from 330-360° depending on the breed.[3] Their eyes are located laterally on the head, giving them panoramic vision along the plane of the horizon with only a small binocular field of about 25-50° where both eyes see the same object.
As prey animals, cattle favor a wide field of view over visual acuity in the center of gaze. Their visual acuity is estimated to be 20/100 based on studies of their retinal ganglion cells.[4]
Bulls Have Dichromatic Color Vision
Trichromatic vs. Dichromatic Vision in Mammals
Mammals typically have either trichromatic or dichromatic color vision. Trichromatic vision relies on three types of cone photoreceptor cells that allow animals to perceive color across the visible light spectrum. Common examples include most primates like humans and monkeys.
Dichromatic vision, on the other hand, only utilizes two cone types. This is more common among mammals like dogs, cats, cattle, and bulls.
Cattle Have S and M Cones But Lack L Cones
Research shows that cattle have both short wavelength sensitive (S) and middle wavelength sensitive (M) cone photoreceptors. However, they lack longer wavelength sensitive (L) cones. This means cattle, including bulls, are red-green colorblind compared to humans and see a limited range of colors.
| Trichromatic Vision | Dichromatic Vision |
| 3 types of cones (S, M, L) | 2 types of cones (S, M) |
| See full color spectrum | Limited color perception |
| True color vision | Colorblindness/color vision deficiency |
Color Perception in Bulls
With only S and M cones, research suggests bulls have dichromatic color vision similar to red-green color blindness in humans. They still perceive colors, but their color spectrum is compressed compared to animals with trichromatic vision.
Bulls likely see variations of yellows, blues, grays, and brightness differences rather than the full range of hues and saturations.
How Bulls See Red
Red is a particularly interesting color when it comes to bulls. Many people believe red triggers aggression in bulls, but studies show red appears dark gray to bulls rather than eliciting a rage response.
Their reaction likely depends more on the context, movement, shape, and contrast of objects rather than simply the color red. So while matadors may opt for a red cape, it likely provides high visual contrast rather than angering bulls.
Motion Detection is Key in Bulls
Limited Color Vision Puts Emphasis on Movement
Bulls have dichromatic vision, meaning they see color in the blue and green-yellow spectrums. This is similar to red-green color blindness in humans. Without the ability to detect reds, bulls rely more heavily on detecting motion to perceive threats or prey in their environment.
The limited color range puts greater emphasis on the bull’s motion detection abilities for survival.
Matadors exploit this limitation by waving the bright red cape to provoke bulls to charge. While humans clearly distinguish the red color, to bulls it appears dark and indistinct from the dark dirt of the bullfighting arena.
The dramatic sweeping movement of the matador’s cape triggers the bull’s prey drive and provokes it to attack.
The Matador’s Cape and Bull Charging Behavior
The movement and posture of the matador cape act as a “superstimulus” that triggers hardwired prey attack behavior in bulls. Specific kinds of motion, such as the sweeping sideways movement of the cape, provoke charging and attack.
Forward pointing horns and heads lowered in attack posture indicate the bull perceives the moving cape as prey to be captured.
Bulls have wide-angle vision allowing them to detect fast motion and changing patterns. Their gaze is drawn to the dynamic sweeping and whipping motions of the matador’s cape. The bull associates this with prey movement and instinctively charges.
The matador relies on the bull’s instinctive reaction to movement and exploits it to provoke bulls to charge repeatedly.
How Pattern and Motion Evoke Charging
Research on bull vision has identified specific patterns and motion dynamics that elicit charging behavior. Vertical patterns, contrasting dark and light signals, and lateral motions similar to retreating prey tend to provoke bulls to charge.
These visual triggers tap into the bull’s innate prey drive.
Laterally moving targets prompt longer charges compared to vertically moving targets. Additionally, higher speeds elicit greater aggressive charging in bulls. Faster moving capes provoke the bull to increase its attack speed and intensity.
Understanding these reactions has allowed matadors to master techniques with the cape that manipulate the bull’s instinctive responses. For bulls, motion and pattern detection are essential survival skills.
Matadors exploit these reactions to create the dramatic confrontations seen in bullfighting arenas.
Other Factors Influencing Bull Vision
Visual Acuity and Field of View
Bulls have decent visual acuity, able to see objects clearly at distances up to about 1,000 yards away (source). Their eyes are set widely apart on their large heads, giving them a wide field of view of about 310 degrees (source).
This allows them to easily detect movement and threats approaching from the sides or behind without having to turn their heads.
However, bulls have a smaller area of binocular vision overlap in front of them than predators like wolves. So while their field of view is very wide, they don’t see fine details as clearly directly ahead of them compared to predators who rely more on binocular vision for hunting.
Nocturnal Vision Capabilities
Bulls don’t see color differences very well, but their vision is well adapted for detecting shapes and patterns (source). This helps them recognize other cattle even in low light conditions. The structure of their eyes and high density of rods allow them to see fairly well at night or dusk dawn periods.
| Vision Capability | Daytime (Photopic) | Nighttime (Scotopic) |
| Visual Acuity | Decent from afar | Poor |
| Color Perception | Dichromatic | None |
| Motion Detection | Excellent | Very Good |
As shown, while some vision capabilities like visual acuity and color perception decrease for bulls at night, their motion detection remains quite effective even in low light (source). This allows them to notice and react to predators or cattle wandering at nighttime.
Effects of Domestication on Vision
The extent of exposure bulls have to humans and artificial lighting conditions may influence their vision over generations. One study found that domestic cattle have more rod photoreceptor cells than wild cattle (source).
This adaptation would help domestic bulls see better at night around barns or pens.
However, very bright indoor lighting could cause issues for them seeing properly when transitioning back outdoors. Overall though, domestication does not seem to have caused major changes yet in innate bull vision capabilities that evolved naturally over centuries (source).
Their eyes and brain vision processing areas remain well adapted to detect motion and changes in their environments.
Conclusion
In summary, bulls and other cattle have dichromatic color vision, meaning they see fewer colors compared to humans due to only having two functioning color photoreceptors. They can perceive some hues like blues, greens, and yellows but likely see reds as a shade of gray or yellow.
More important for bulls is detecting movement and patterns, which explains their charging behavior towards matador capes. While bull visual abilities are more limited than human sight, their eyes are well adapted for detecting threats and chasing prey across open fields.
Understanding the visual world of bulls provides insight into their behavior and biology.
