Vision
What Do Rabbits See?
by Dana M. Krempels, Ph.D.
Many house rabbit "parents" are curious to know what the world looks like to their lagomorph companion. Why does it seem difficult for my bunny to find food right in front of his face? Why is my bunny so easily startled or frightened if I walk into the room holding a box or a grocery bag? Can my rabbit see colours?
The first thing to remember is that a rabbit's visual system evolved under evolutionary pressures completely different from those which "designed" your eyes. We human primates, like our simian cousins, have forward-placed eyes which confer binocular vision and depth perception. This is essential for an animal originally designed to leap through the trees. Also, we have excellent colour vision, a trait which helped our ancestors to find ripe fruit and tasty flowers in the forest canopy.
On the other hand, the rabbit visual system is designed--not for foraging and locomotion--but to quickly and effectively detect approaching predators from almost any direction. The eyes are placed high and to the sides of the skull, allowing the rabbit to see nearly 360 degrees, as well as far above her head. Rabbits tend to be farsighted, which explains why they may be frightened by an airplane flying overhead even if their human companion can barely see it. (It could be a hawk! Run!)
The price the bunny pays for this remarkable field of vision is a small blind spot directly in front of his face, but forward-placed nostrils and large, spooning ears compensate for that minor loss of predator-detecting space. For an animal to have binocular vision, the field of view of both eyes must overlap to some degree. The central blind spot in the rabbit's field of view precludes a three-dimensional view of nearby objects. When your bunny cocks her head and seems to be looking at you "sideways," she is actually looking as straight at you as is possible for a bunny. As far as we know, she does not have a primate's level of depth perception at such close range.
What about colour vision? In general, vertebrates have two different types of photoreceptor cells in their retinas: rods and cones. Cones confer high resolution, and, if more than one cone type is present, they also confer the ability to perceive various wavelengths of light as distinct colours. For example, we humans have three different categories of cone--their maximum sensitivities in the red, blue and green regions of the spectrum. The differing sensitivities of each cone type enable us to perceive different (visible) wavelengths of light as the colours of the rainbow.
Behavioural studies published in the early 1970's indicate that rabbits do have a limited ability to discriminate between some wavelengths of light, perceiving them as different colours. Evidently, they can discriminate between the wavelengths we call "green" and "blue." Although rabbits may not perceive green and blue the way we do, they *can* tell them apart. This means they have limited colour vision, probably conferred by two different categories of cone cells (blue and green).
The other type of photoreceptor, the rod cell, confers high visual sensitivity in low light situations, but relatively poor resolution (i.e., a "grainy" picture). The rabbit retina has a much higher ratio of rods to cones than the human retina has. Although a rabbit can see better than a human in low light conditions, his low light image has much poorer resolution (clarity) than the daytime images formed by your cone-rich, primate retina.
Now you may wonder: "Can my rabbit see me clearly, or am I just a big blur?" As you read this page, you are focusing on the letters with a very tiny part of your retina called the fovea. This is a minuscule, cone-shaped depression in the retina, lined wall-to-wall with high resolution cone cells.
Rabbits, too, have small retinal areas with more cones than rods. However, this area centralis is not indented, and it has far lower cone density than our fovea has. The image formed by the area centralis is relatively "grainy" compared to the one formed by your fovea, but it serves the rabbit well. Using this image, your voice, body movements and scent as cues, your rabbit can recognise you (his favourite human)--as long as you're not carrying a scary box that completely changes your familiar shape!
Knowing a little more about how another creature sees the world allows us to come one step closer to understanding its behaviour--and modifying our own to make life happier for everyone. Remember that the next time your rabbit gazes at you with those deep, ancient eyes.
Source: What Do Rabbits see?
The following link contains an in depth discussion about rabbit eyes and vision:
Blindness
Blind rabbits can live quite wonderful lives. The key to keeping them at ease is to remember that they are prey animal, rather than predators (as dogs are). Prey animals don’t investigate unusual noises — they avoid them. All rabbits are averse to change to one degree or another — and a blind rabbit will be more so.
One key to a blind rabbit’s comfort is to let him be familiar with his environment — don’t rearrange the furniture regularly, etc. You’ll be surprised how quickly a rabbit will master the layout and start romping around in confidence.
Because being able to safely retreat is a part of making a rabbit feel secure, a blind rabbit is more likely to be distressed when his regular traffic routes are disrupted.
Rabbits have good hearing, so you can train a blind rabbit to specific voice commands. A rabbit will also rely on his sense of smell. A blind rabbit may be more likely to chew so bunny-proofing will be important, too.
Keep familiar scents around for your blind rabbit. Most bunnies object to having their cages cleaned (going into a frenzy of rearranging after you’ve completed) so make sure not to do a total overhaul on their cage — always leave something that smells familiar to them. That could be a section of fleece fabric, a stuffed toy, a scrap of carpet, etc.
The following link has a really informative article about blind rabbits - including the causes and symptoms, and how to care for them -
Red Eye Scanning
"Some rabbits have an odd behaviour called "scanning." It seems to be most prevalent in albino rabbits, but no one knows why. It may be an exaggerated motion associated with the normal nystagmus of the eyes. -- Nystagmus is the natural, microscopic movement that every vertebrate eye makes constantly--including ours! It's what makes vision possible. As our eyes microscopically change the visual field at this tiny level, constantly (we are not aware of it, and you can't see or feel it), the eye's photoreceptors are constantly stimulated by the ever-changing light hitting them. This is why we can see. Without nystagmus, we would not be able to see. -- Some people have suggested that albino rabbit "scanning" (the side to side movement of the head you're seeing) is an "outgrowth" of normal nystagmus--but no one knows for sure. -- But the bottom line is that it's a genetic trait that is not harmful, and it's nothing to worry about."
Source - Dana M. Krempels, Ph.D. August 8th, 2007
"Scanning" or "tracking" is a vision-related rabbit behaviour that can cause concern in those unfamiliar with it. Some rabbits will sit and weave or sway slowly back and forth. They appear to be causing motion in order to see an object that is within a short distance of themselves. This behaviour is also observed when carrying a rabbit facing forward. Head motion is thought to be a means of enhancing distance measurement. When the eye is moving, close objects move faster than distant ones." - "If your rabbit is a scanner--most common in pink-eyed rabbits--she will regularly scan; it won't be a sudden-onset behaviour. As with so many other aspects of rabbit behaviour and health, sudden changes indicate health problems." -- NOTE: -- "IS IT A STROKE? If your rabbit, especially an older rabbit, suddenly appears unstable, disoriented with eyes that "twitch," it's very important to note whether the eyes are moving up and down or back and forth." - "This eye twitching is called nystagmus. Up and down eye movement signifies a brain problem, whereas back and forth signifies an inner ear infection or other problem. In either case, the rabbit needs to get to her veterinarian as soon as possible."
Source - San Diego HRS
Further Reading -
Red Eyes, Eye Scanning & Rabbit Vision