Reasons why eyes glow in the dark in cats: a scientific explanation. Why does a cat's eyes glow in the dark Why does a cat's eyes not burn at night

Cats are one of the most beautiful animal species on our planet. Representatives of the cat family are distinguished by quiet graceful movements, independence, soft fur and, of course, sparkling eyes. Because of this property, cats have long been considered magical animals, companions of witches, fraught with many secrets. Why do cats eyes glow in the dark?

Shining eyes - magic or physiology?

In fact, the glow of cat eyes is, in some way, a delusion. The fact is that on the inside of the eye of a cat (like any other animal capable of nocturnal existence), there is a special transparent ("luminous") layer - the tapetum. It consists of guanine (a nitrogenous base) and various pigments that give the eye of an animal one color or another (in cats it is yellow or green, in dogs it is dark brown or green-blue, in fish it is milky white, etc.). The shiny layer plays an important role for cats. The fact is that not the entire light beam is perceived by photoreceptors. The tapetum reflects the "remnants" of light to the retina, resulting in much more signals to the brain. In this regard, the answer to the question of why cats have glowing eyes becomes quite obvious: so that they can see better at dusk and, accordingly, hunt.

Do cat eyes glow in pitch darkness?

But the question of why a cat's eyes glow at night is not formulated quite correctly. And the answer to the popular riddle "How to find a black cat in a dark room?" there really is only one option - turn on the light. In absolute darkness, the tapetum simply has nothing to reflect, respectively, the “glow” will arise only if the light source is at least of minimal intensity. And if you point in the direction of the animal, for example, a flashlight, the eyes will “flash” very brightly.

A reflection from a street lamp, a glare from a crystal chandelier, a light from a tablet or phone screen can “catch” the eyes. Of course, one of the main night sources is the moon. Therefore, even if it seems to us that the room is very dark, the lights are turned off, you can still see the same brilliance.

Sometimes it is so intense that it is even a little scary. The “strength” depends on the angle at which the light beam falls on the eye, and at which the person looks at the cat. The brightest reflections are rays that hit the retina at an angle of 45 degrees, if at the same time look exactly "in the face" of the animal.

Cats themselves do not feel this effect. This conclusion can be drawn from the absence of squinting during the appearance of the glow.

But if a bright beam falls directly, the cat will definitely close its eyes. After all, in this case there will be an “overload”, a re-irritation of the light receptors of the retina. In turn, in a bright room during the day, it is almost impossible to catch the glow effect, because the light penetrates the eye completely, and the animal sees well without any reflection.

red eye

It would be interesting to note that a person's eyes can also "glow". Of course, this property is expressed many times less, because we are spared the need for night vision. However, a similar layer still exists in the human eye. That is why in conditions of not very good lighting from a bright flash, the eyes begin to cast red in the photo.

Thus, the glowing eyes of cats are not magic at all, but an adaptive element.

It often seems to an observer from the outside that cats' eyes "glow". In fact, this returned luminous flux looks like the glow of the eyes. That is, the glow of the cat's eyes is nothing more than a reflection of the light flux through the pupil of the animal that has entered the eye. Moreover, the eyes of cats can glow in different colors.

Why do cats have eyes glowdifferent color? The point is that t the apetum, which covers the fundus of the eye of animals, looks like mother-of-pearl or shiny fish scales. And depending on the impurities of pigments, it can have a green, blue, yellow tint. From here, the eyes of a cat or dog “glow” in green, blue or yellow (Fig. 1).

Fig.1 Why does a cat's eyes glow in a photo.

The eyes of a cat can also glow in red. This is due to one feature of the placement of the tapetum. This reflective shell can cover the entire fundus or only part of it. Have a different shape - a triangle, a rhombus, a crescent.

And then a very interesting effect is obtained - the tapetum gives, say, a saturated green glow, and where it is absent, the fundus will reflect a weaker Red color.

When shooting with flash, you can get a picture in which the eyes of a dog or cat will glow in different colors. Moreover, there are cases when two colors are visible at once in one eye. This means that the tapetum in this case covers only part of the fundus (Fig. 2).

Fig.2 The cat's eyes glow in different colors

Therefore, when owners of cats and dogs say that their pets have eyes of different colors, the reason may be in the features of the tapetum.

Thus, the eyes of cats "glow" due to the reflection of incoming light from the tapetum covering the fundus.

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Like most other predators, the cat prefers night hunting. Thanks to sharp hearing, sense of smell, vision, as well as a completely silent gait, the animal is confident even in the darkest room. The slightest extraneous sound, and in one jump the cat successfully overtakes its prey.

Good eyesight allows the animal to see. In the daytime, the pupils narrow so much that they turn into narrow slits. With the onset of darkness, they expand and absorb even the weakest stream of light. At night, the pupils of cats can reach up to 14 millimeters, or even more.

Eyes, like those of a person, are directed forward, which allows her to focus both eyes on a specific object, and calculate the distance to it with the slightest accuracy. Therefore, sometimes a few seconds are enough for a cat to make a jump and catch a gaping prey. Those spaces that the animal sees with both eyes overlap by 45% in front, which makes it possible to see the same object simultaneously with both eyes.

If you shine a light from a hand-held flashlight on a cat, you can see how its eyes begin to glow. This is due to the fact that the back surface of the entire eyeball of a cat is covered with a special substance that vaguely resembles polished silver. It reflects any ray of light that enters the eye of the animal. The reflected light does not scatter around, but returns exactly to the point of its origin.

Unlike humans, a cat sees the whole world as pale and gray. She cannot distinguish colors because many of them are simply not available to the cat's vision. For example, a red shade for cats does not exist at all. However, this does not bring inconvenience to fluffy "purrs" at all, since their main prey are mice and birds, and they themselves are gray in color.

For more than one thousand years, people have lived next to cats. These amazing and mysterious animals captivate a person with their refined grace, beauty and gentle manners. At different times, mankind idolized cats, equating them to deities, as, for example, in ancient Egypt. In Japan, tailless cats were revered, so the Japanese Bobtail breed appeared. Figurines of such cats can still be found in many houses of the Japanese islands. And in the Middle Ages in Europe, people were afraid of cats, burning black cats at the stake along with their mistresses, considering unfortunate women to be witches.

A lot of superstitions and signs were associated with cats, until now, some believe that meeting a black cat on the street does not bode well. But still, cats managed to conquer human hearts, these fluffy creatures live in almost every family. And no matter how well we know our furry friends, they are still surrounded by many secrets and mysteries. How do cats anticipate earthquakes, how do cats find their way home several hundred kilometers away, and, of course, why does a cat's eyes burn in the dark? Burning cat's eyes in the dark have become the occasion for many stories, fairy tales, and this image is often used in cinema.

Nonetheless There is a completely scientific explanation for the effect of the glowing eyes of a cat.. Like most predatory animals that are nocturnal, cat eyes are arranged in such a way that any light, even a faint reflection of the moon or the glow of stars, can be reflected in them. The eyes themselves do not produce any light, of course.. You can do a little experiment yourself. If you close a cat in a dark room without windows, then make sure that in absolute darkness her eyes do not glow.

The cat's eyes are able to reflect the light of an external source: a slight glow of the night sky, a bright flash of car headlights - and the cat's eyes become like small spotlights. The whole point is that the inside of the cat's eye is covered with a layer of shiny transparent cells, which is called tapetum. Silvery tapetum is very similar to a mirror, and it is he who is able to reflect light. Even the weakest beam of light, falling through the lens and cornea, is not completely absorbed, but is reflected back by a thin beam of light. This feature helps cats see well at night.

The color of the glow of the eyes in various animals depends on the pigment that is in the tapetum. In cats, it is most often yellow and green. Other shades may be much less common. For example, in Siamese cats, the tapetum pigment has a crimson color.

A cat's eyes are seven times more sensitive than a human's.. But even in humans, a weak glow effect can be observed if a bright flash is used. So sometimes in color photos, people's eyes can burn in red.

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The cat is a dexterous hunter, and her eyesight is excellent even at night. But such a unique feature of the cat's eyes as the ability to glow in the dark did not always bring only one benefit to this animal.

The Holy Inquisition, which was active in medieval Europe, declared cats minions of the devil and witch offspring.. The reason for this was the activity of cats in the dark, as well as vertical pupils and eyes of these little predators burning with “hellish fire in the night”. In addition, pagans revered cats, and the early Christians tried in every possible way to destroy the roots of alien beliefs. In the Middle Ages, thousands of cats were burned alive in bonfires and drowned in sacks along with alleged witches. These brutal reprisals continued until the 19th century, which marked the beginning of the Age of Enlightenment.

However, the barbaric attitude towards cats was typical only for those European countries where the Catholic Church dominated. The pagans of Africa and the Eurasian continent have always revered the cat as a sacred animal. In Russia, since ancient times, cats have been considered the keepers of the hearth, and before the advent of Christianity, they were associated with the names of the deities of Rod, Veles and Mokosh. And the unique vision of these four-legged animals was explained by the need to travel between light and darkness - the worlds of the living and the dead, people and gods.

Russian Orthodox Christianity has retained this favor for cats despite their unusual habits. So, to this day, a cat is allowed to enter an Orthodox church and roam around it wherever it pleases. For example, the dog is forbidden to walk even on the territory next to the church.

Why do eyes glow

In the strict sense of the word, the eyes themselves do not glow in cats, but only reflect light. This effect is explained by the unusual device of cat vision. The mechanics of the pupils and the photoreceptors of the bottom of the eyes in these animals are adapted to a greater extent to work in low light, because the cat is predominantly a nocturnal predator.

Behind the retina of these animals is a special layer - the tapetum, which contains a large percentage of photoluminescent pigment.. The light falling on this layer is reflected as from a mirror and is amplified several times, allowing the animal to see perfectly in the dark. For this, weak light from the stars is sufficient. At the same time, in the dark, the pupils of cats open wide to let in as much light as possible into the eyes.

Maximally dilated pupils occupy almost the entire area of the iris, reflecting the light flux from the entire area of the fundus. If at this moment a beam of more or less bright light hits the cat's eyes, a glow effect occurs. And if the light source is bright, such as light from car headlights, a flashlight or a flashlight, then the cat's eyes literally flare up with bright fire.

Almost all predators (especially nocturnal ones) have a luminescent pigment in the retina, and humans too. The difference is that its amount in the retina of cats is much higher. For example, dog eyes also partially reflect light in the dark, and human eyes often “light up” during a camera flash, which is why the “red-eye effect” appears in the photo.

Green, yellow, red - cats' eyes glow differently

The reflective layer of the retina (tapetum) is of two types - tapetum lucidum and tapetum nigrum. Most cats have the first type, which is highly saturated with luminescent pigment. It looks like mother-of-pearl, and its color varies from yellow to green. At the same time, there is more golden-green in the center, and bluish-green along the edges. The eyes of cats with this type of tapetum glow with yellow, yellow-green or blue-green light.

The hue of the glow of the eyes also depends on the angle of incidence of the light rays. If light hits a cat with a well-pigmented tapetum directly into the center of the pupils, the glow will be as bright as possible, light yellow or greenish-gold. In the side light, the eyes will shine with turquoise, bluish or purple light.

The eyes of kittens up to 3 months old sparkle in the dark with faint reddish reflections, because their retina is still poorly pigmented., and a non-bottom reflective layer has formed. As the kitten matures, the retina accumulates luminescent pigment, and the eyes begin to glow yellow or green in the dark.

But in some cats (for example, in Siamese), the tapetum may remain crimson for life. In the dark, the eyes of such cats gleam red, since the light entering through the pupils in this case is reflected to a greater extent from the blood vessels. This effect is generally seen predominantly in blue-eyed cats. And all because they got tapetum nigrum - a variant of the tapetum with a low content of luminous pigment.