Why do cats' eyes glow in the dark?
When they say about a person that he “sees like a cat,” this is a big stretch, since a cat’s vision is very different from ours. Cats see well in light levels 10 times lower than what we can see in. At the same time, in good lighting, cats are worse at distinguishing details than we are. This is the first feature cat vision. It seems to be specialized in the perception of dimly lit space. This is why cats prefer shaded rooms where they like to rest and perform their toileting. And, naturally, those of them who like to hunt mice are forced to do this in low light conditions, because their victims lead a twilight and nocturnal lifestyle. But cats, in addition to hunting, also have to make love at night, which we can guess by listening to the heartbreaking screams of March cats at night.
During the daytime, a cat's pupils narrow significantly and turn into small dots. And at night they are wide open, letting all possible light into the eye.
The back wall of the eye is covered with a special substance that resembles polished silver. It reflects every ray of light that enters the eye. That's why cat's eyes sparkle in the dark like lit lanterns if you shine even a small stream of light on them.
http://www.potomy.ru/fauna/952.html
In the choroid, consisting of a network of feeding eyes blood vessels, at the exit site of the optic nerve there is a layer of cells with crystalline inclusions - a speculum. In the depths of the eyeball (retina) with visual cells - rods and cones. In a cat, as a twilight animal, the retina of the eye is mainly equipped with rods, and only in the central part of the retina, in the area of acute vision, are cones concentrated.
More recently, it was believed that cats do not have color vision at all, but it has now been established that cats are still able to distinguish, although worse than us, several colors. But what they distinguish much better than us are shades gray, up to 25 shades.
This visual feature can be explained by the coloring of their victims.
Watching a cat or kitten running after a ball on a string, it is easy to establish that they react much more acutely to the horizontal movement of the toy. So, a ball that you roll on the floor always causes an active pursuit reaction in a cat, while a ball that you move up and down in front of it, it reacts more sluggishly. This is a reflection not only of her hunting instincts, since mice and voles move only in the horizontal plane, but also of her vision. It has been established that a cat tracks the horizontal movement of objects in more detail and sharper than the displacement of the same objects in the vertical plane.
Cats have a good view of nearby space, but in the distance the contours of objects look slightly blurred to her. A cat's two eyes are located close to each other and point forward, creating an overlapping field of vision.
Thus, we see that many features of cat vision are in one way or another connected with solving the main life task - obtaining food.
The fauna is diverse. Even pets that have lived side by side with people for thousands of years sometimes make us wonder and ask questions. For example, why do cats' eyes glow in the dark? Perhaps you have already noticed the eyes of your pet sparkling in the semi-darkness, watching you from above. So why don't human eyes glow the same way?
Historical background: cat's eyes and superstitions
Cats' eyes glow due to reflection.
Cats in Europe, starting from the 14th century (the beginning of the Catholic Inquisition), were considered messengers of the devil and assistants to witches. The origins of these superstitions were supposedly glowing in the dark cat eyes, their vertical pupils and natural cat independence. Black cats were especially disliked, apparently for their fantastic ability to dissolve in the dark. Embittered fanatics burned beautiful girls and their cats, thereby permanently impoverishing the gene pool of both in nearby European areas.
Interesting fact: In ancient times, cats were considered protectors, hunters, and sometimes even idolized. Since ancient times, cats have been considered special animals; pagans believed that cats were messengers of the god Rod, the so-called “prelagatai”, observing what was happening on earth and transmitting the collected information to the gods. The legends that have come down to us say that Makosh, the ancient Slavic goddess of water, asked the clan for an observer to look after the people. Rod thought and created a furry domestic creature that walks between the boundaries of reality and will warn people about approaching trouble. He distributed one to all the gods and sent several to earth so that they would multiply and protect the home of each family.
Why do cats' eyes actually glow?
But biology does not agree with superstitious people. Moreover, cat's eyes do not glow in the literal sense of the word: they only reflect light.
Cats see better in the dark than humans.
To simplify, the process of obtaining an image by the brain can be described as follows: light reflected from objects passes through the pupil into the lens, through it it is imprinted on the retina, which captures the light and rewrites it into an electrical signal (neural impulse) entering the occipital lobe cerebral cortex. At the stage when light hits the retina, the so-called “glow” of a cat’s eyes appears.
Behind the retina is a layer of reflective cells– tapetum, special layer choroid. It is divided into two types - tapetum lucidum and tapetum nigrum. In all species of animals it is expressed differently, and even within a species, depending on the breed, the ratio of one and another type of tapetum, its location may change. Tapetum L. in cats is located in the form of a diamond or triangle and occupies a large area. Light hitting the retina passes through it, is reflected from the tapetum and falls back on the retina, strengthening the signal and providing a better image. That is why cats only need the weak light of the stars and the moon - they have eyeballs oh the built-in amplifier that allows them to see at night. And seeing eyes sparkling in the dark, we are observing just reflections of reflected light.
Interesting fact: This system for improving night vision is another remarkable invention of evolution. Not only cats can boast of eyes sparkling in the darkness: all nocturnal predators, to one degree or another, have similar abilities. Owls, for example, see 10 times better in the dark than cats, and are able to detect the movement of a mouse 300 meters away; but during the day they are practically helpless, since their eyes are too sensitive for bright daylight. The marsupial loris, a resident of Australia, has huge eyes and ears, as it hunts insects at night, and has adapted to hear and see even a praying mantis crawling by.
Green and red
The color of the reflected light is also explained by the properties of the tapetum. Tapetum L. produces a predominantly yellow, green, and bluish glow. Tapetum N. practically does not change the reflected light, so we see a red glow - from the blood vessels of the choroid. Depending on the angle of incidence of light and the location of the tapetum, we can see how the eyes glow green - when reflected from Tapetum L., or a reddish dim glow - these are reflections from Tapetum N. It is interesting that the eyes glow red even in humans - remember these reflections on Polaroid photos, red eye effect? It is also a reflection of the flash in our eyes. Humans do not have such a powerful tool for enhancing night vision as cats do, so our tapetum is practically invisible - unless you point a flashlight directly at the eye, of course.
Cats are one of the most beautiful views animals 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 since ancient times 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 somewhat of a misconception. The fact is that on the inside of a cat’s eye (like any other animal capable of nocturnal existence), there is a special transparent (“luminous”) layer - tapetum. It consists of guanine (a nitrogenous base) and various pigments that give the animal’s eye a particular color (yellow or green in cats, dark brown or green-blue in dogs, milky white in fish, etc.). Shiny layer plays important role for cats. The fact is that not the entire light beam is perceived by photoreceptors. The tapetum reflects the “remnants” of light onto the retina, as a result of which many more signals enter the brain. In this regard, the answer to the question why cats’ eyes glow 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 entirely correctly. And the answer to the popular riddle “How to find black cat in a dark room? There is really only one option - turn on the light. In absolute darkness, the tapetum simply has nothing to reflect; accordingly, a “glow” will appear only if there is a light source of at least minimal intensity. And if you point, for example, a flashlight towards the animal, the eyes will “flare up” very brightly.
The eyes can “catch” the reflection from a street lamp, the glare of a crystal chandelier, or the light from the screen of a tablet or phone. 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 that same shine.
Sometimes it is so intense that it is even a little scary. The “force” depends on the angle at which the light beam falls on the eye, and at which the person looks at the cat. The brightest reflected rays are those hitting the retina at an angle of 45 degrees, if you look exactly “in the face” of the animal.
The cats themselves do not feel this effect in any way. This conclusion can be drawn by the absence of squinting during the appearance of the glow.
But if a bright beam falls directly, the cat will definitely close her eyes. Indeed, in this case there will be an “overload”, overstimulation 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 completely into the eye, and the animal sees well without any reflection.
Red eye effect
It would be interesting to note that a person’s eyes can also “glow”. Of course, this property is much less pronounced, because we are freed from 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, the eyes begin to glow red in the photo from a bright flash.
Thus, glowing eyes in cats it is not magic at all, but an adaptive element.
Even a child knows that cats' eyes glow in the dark, but adults cannot explain why. No, cats do not produce light, and the mysterious reflection of their eyes is a consequence of special physiology and a tool for survival. Curious to know the details? Read on, below we will look at all the complex nuances in simple language.
Cats have been domesticated since ancient times. It’s interesting that no matter how hard people try to completely domesticate the purr, nothing works. Cats have been and remain versatile and the most successful hunters in the world. In everyday situations, cats are calm and affectionate, but have you ever seen a purr when angry? Their strength, agility and ability to inflict wounds are so deeply embedded in their DNA that even the most peaceful pet can greatly surprise the owner.
Cats belong to a large family and are relatives of pumas, lynxes, ocelots, tigers, and lions. People became interested in domesticating these magnificent creatures even before our era. It’s interesting, but cats became people’s companions earlier than dogs. How an ancient, vulnerable man came up with the idea of encroaching on the will of a universal predator is not entirely clear. However, the fact remains that cats have lived next to people for centuries, they are loyal in their own way, but there is still something wild in them. If you carefully observe your pet, you will find in its gait and manners many features similar to wild cats. There is only one reason: the cat is a hunter and its skills have not atrophied despite domestication.
For what merits did the cat receive the title? best hunter? This list is quite long, but there is one key factor - success. It doesn't matter if the cat is wild or domestic, it will have a number of skills:
- Silent gait and ability to sneak.
- Sharp teeth and fangs with grooves that allow normal breathing while holding the victim.
- Acute sense of smell.
- Sensitive hearing.
- Agility, flexibility, ability to move in difficult terrain.
- Acute vision and the ability to record any movements of the victim at a great distance.
- Wide angle of lateral vision.
- The ability to hunt in the dark as in the light is the main and very remarkable feature of cats, given that they are not nocturnal animals.
Cats are generalists; they can hunt during the day, at dusk and at night, while most predators hunt at certain times of the day. The eyes of a cat are very sensitive and vulnerable, at the same time they are the main “weapon” and mystery of the purr.
Features of cat vision
Cat's eyes function in the same way as human eyes, with only one difference - humans do not see well in twilight and darkness. Let's briefly look at the structure and features of a cat's eyes. So, there is such an expression - the eyes are the brain out. Although it sounds a little strange, this statement is completely justified. The eye is a sensory organ that has direct contact with both the brain and the outside world.
The outer layer of the eye consists of three layers: sclera, vascular tissue and cornea. The sclera is like an elastic film that helps maintain correct form eyes. The vascular layer nourishes the outer chamber of the eye. Blood constantly circulating in the vessels delivers nutrients and oxygen. With the blood and through the same vessels, decay products are removed from the outer chamber of the eye. Next is the cornea layer. This is the very part by which eye color is determined. The cornea has a hole - the pupil, which expands and contracts at the command of nerve impulses. The pupil performs the function of focusing vision, that is, thanks to it, the cat can see objects nearby and far equally well.
The next important organ of the eye is lens. This part of the eye is not solid, as you might think; its structure resembles a viscous liquid. The lens refracts light rays transmitted by the sclera and pupil. The rays of light are collected into beams and travel further to the retina.
Note! It is believed that too much light can harm the health of a cat's eyes.
Retina, this is the most sensitive part of the eye, it is dotted with photoreceptors different forms: cones and rods. Each type of receptor is responsible for the perception of images in the dark and in the light, so a cat has approximately the same number of them. The retina, like the pupil, has a round hole; it connects to the optic nerve. The retina, struck by light rays, transmits electrical impulses to the nerve, which carries information to the brain. Optic nerve entwined with a large number of blood vessels that supply the second (dorsal) chamber of the eye.
This is interesting! The holes in the retina create a blind spot, which is located exactly in the middle of the picture seen.
It is interesting that when passing through the lens, the rays of light are refracted so that the picture seen is turned upside down. The brain, which cooperates with the vestibular apparatus, is responsible for the correct perception of the picture. In its turn, vestibular apparatus is responsible for the sensation of the horizon, that is, thanks to this organ, the cat understands where is up and where is down and in what position it is in relation to the support.
In addition to the eyeballs, the external or protective organs of the eye play an important role in the visual acuity of a cat. Eyelashes protect your eyes from damage and your eyelids from drying out. Blinking is a reflex, and every time the cat closes its eyelids, the eyes are moistened with tears and secretions of the mucous membranes. Main role The conjunctiva plays a role in moisturizing the eyes - the layers of cells located on the lower and upper eyelids. Cats also have third eyelid or nictitating membrane, it is transparent and thick fabric, attached to the muscles of the eyelids. When a cat blinks, the nictitating membrane also closes and helps keep the eye moist.
This is interesting! Thanks to the nictitating membranes, the cat can sleep with the eyelids open without harm to the eyes or the threat of dryness. In humans, this membrane is atrophied, but for cats it serves as a tool to “ward off” larger predators.
Unlike humans, cats have oval pupils that can expand to cover almost the entire area of the iris and narrow to barely noticeable slits. If you compare the proportional structure of the eyes of a cat and a human, it becomes clear that the former are superior to the latter in visual acuity. At the same time, a person is able to distinguish between seven colors and three spectra, while a cat sees the world in bluish-green light. It is known that purrs can distinguish some shades of yellow and orange, but they see red as gray.
Cats' eyes are located on the front of the head and point forward. This type of vision is called binocular. In comparison, herbivores have eyes on the sides of their heads and this type is called peripheral. The cat has no blind spot, since the brain receives information from both eyes simultaneously. Herbivores have a blind spot, it is right in front of their muzzle. This difference is due to the fact that predators do not attack head-on, but attack from the side or from behind.
This is interesting! The viewing angle of a cat is approximately 285°, while a person covers only 210° of what he sees.
About glow in the dark and more
Purring eyes shine different colors: blue, red, green, yellow, and sometimes purple. It is believed that the color of the reflection varies depending on the ratio of the number of cones and rods (photoreceptors), although this version has not been proven. The gases of cats do not glow (do not produce light), but rather reflect, that is, reflect rays of light. You may have seen sparkling eyes in pitch darkness, but this only proves the superiority of cats over humans. Reflection is impossible if there are no light sources in the room, even very weak ones. In complete darkness, anyone is blind, because the eyes do not see a picture or objects, but rays of light reflected from them.
Do you think that this feature is unique to cats? This is not true, people's eyes also glow, but it is not so noticeable. The red eye effect in the photo is direct proof of this. The glare of a cat's eyes is more intense due to its physiology.
The back, hidden part of the eye has a concave shape. In front of this fossa is the lens, which acts as a lens. You played as a child magnifying glass? Directed Sunbeam on paper? Much the same thing happens when you see the reflection of a cat's eyes. Note that a cat’s eyes glow not only in the dark, but in the daytime this phenomenon is invisible.
This is interesting! It is believed that cats can see seven times in the dark better than people. It is difficult to realize this, but this is exactly the ratio that was voiced by scientists.
The reflector that allows the lens to be used as a lens is called a tapetum. In this case, it is necessary to distinguish between the glow effect and the so-called tapetum effect. The fact is that in some spiders and even mollusks, glowing eyes are observed, although due to physiology it is impossible. When the eyes reflect light contrary to physiological structure, this is called the tapetum or lucidum effect.
The tapetum is located just behind the retina, the structure resembles a dense, pearlescent film. In zoology, the tapetum layer is called the speculum. It is interesting that the structure of the tapetum different cats is the same, but its chemical composition may be different. In some cats, the mirror is more pearlescent and the eyes glow brighter; in others, the tissues of the tapetum are pigmented, which gives a rare violet glow.
Behind the tapetum is the fundus of the eye, which also has a shiny, slightly pearlescent surface. This is why the glare in the eyes is characteristic of many warm-blooded animals, but in cats it is more intense. It is known that the tapetum may not completely cover the cat’s fundus, which will affect the shape of the eye glow you see.
One of the observations of the color of the reflection of the eyes led scientists to an interesting conclusion. In cats whose fundus is not completely covered with tapetum, eye glow of varying intensity and even light may be observed. The fundus gives a red sheen, and the tapetum is green; in the case of partial coverage, the colors can mix and form new ones (blue, violet, yellow).
How to explain to children
If your interest in this topic was sparked by a child's question and you are looking for an easy way to teach about the structure of a cat's eyes, the video below will help you:
The baby is still very young, but very interested by the question asked? Well, fairy tales will help you. Usually, in order not to mislead the child, they talk about a cat that got lost in the dark. The plaintive call of the animal was heard by the moon or the lunar sorceress. Taking pity on the purr, she endowed the cat’s eyes with a special property: collecting light in the darkness of the night. The cat returned home and everyone lived happily ever after.
As you can see, this fantastic story tells about the real reason for what is happening, but in a soft and understandable form for a child. It’s up to you to decide whether to use real data or imagine something unnatural, but keep in mind that most strong beliefs are formed precisely during the period of whys.
Myths and legends
Do stories about the structure of cats' eyes and reflective layers seem boring to you? Well, the glow of a cat's eyes can be explained in more ways in an interesting way, attracting mysticism and old fads. In ancient times, for their ability to sparkle with their eyes, cats were considered servants of the devil and were greatly disliked. To strengthen their authority, rulers and especially churches publicly dealt with the purrs... not in the most humane ways. People were encouraged to fear and not want to go into details. The public reaction was predictable - seeking protection from the rulers and the church.
The apogee of the persecution of cats “coincided” with the witch hunt. The Inquisition pursued only one goal - to instill fear in people, to make lost people out of the people, obeying them in everything. The tactics were successful and so intense that there were no cats left in some regions of Europe. Retribution came quickly... in the form of a terrible epidemic of bubonic plague.
The absence of cats led to a disruption in the food chain; the cities were overflowing with rats, which “brought” the virus. Realizing where salvation lay, despite intimidation from religious concessions, the remaining cats of Europe were collected and brought to the infected regions. Naturally, there were not enough European purrs and cats began to be imported from Asia. Saving humanity from death, cats have earned a positive reputation and received the status of “man’s friend.”
The glow of a cat's eyes Ancient Egypt explained differently. According to legend, Bastet (the goddess of love, fun, joy, beauty, hearth) came to people in the guise of a cat. In addition, cats served the goddess in their “natural” form, they drove the Bastet carriage across the sky. In Ancient Egypt, cats were revered; many beliefs and traditions were associated with purrs, which is described in detail and interestingly in the video below:
In Ancient Rome, purrs were a symbol of independence, freedom and independence. Considering the warlike nature of the Romans, the qualities of the cat deserved special respect. There were also legends of bravery. According to one legend, a large circus in Italy lost its four-legged performers, thanks to the cat, which was able to get out of captivity and freed its “colleagues.” Naturally, according to legend, the circus owner was a terrible and cruel person, people were afraid of him... but they silently but dutifully sympathized with the animals.
The Romans also explained the glow of a cat's eyes in their own way. According to this version, the cat was endowed with the gift of lighting the way in pitch darkness. This event took place after the acquaintance of the purrs and the goddess named Freedom (Libertas). The goddess was so amazed by the combination of independence, independence, devotion and affection that she decided to mark the cat with a special “sign”.
In Japan, the attitude towards cats was twofold. Purr was feared and respected, which is natural, given the lack of information of those times. For quite a long time in Japan, cats had their tails cut off, believing that this part of the body contained all the evil... the rest of the cat, as you understand, was considered good. Incredibly, this ridiculous tradition lasted almost a century.
Later, attention was switched from the tail to the eyes, which glow in the dark. Suspecting something was wrong, namely the prospect of being punished by the gods, the Japanese “accepted” cats as mystical animals. Murlyk were settled in temples, and with their help they communicated with the gods. Quite quickly, the glow of a cat’s eyes came up with a special meaning. It was believed that if a person saw a magical reflection, then a big joy, luck and good fortune.
Glowing cat eyes served as the basis for the emergence of a huge number of superstitions, fairy tales and hypotheses. Since ancient times, people have been interested in why cats' eyes glow in the dark? What are the reasons for this effect in nocturnal animals? How does this help cats see perfectly and why don’t humans have a similar feature?
Scientific explanation
In the dark, cats' eyes glow due to their ability to reflect light that hits them. By themselves, they are not able to produce any radiation, so in complete darkness there will be no glow. The principle of operation of a cat's visual organs is the same as that of human eyes, but there is one significant difference that causes the glow at night - the tapetum.
The inside of a cat's eyes is covered with a layer of transparent cells called the tapetum. It is the similarity of this layer to a mirror that causes the reflection of light and, as a result, the glow. Even the faintest reflection, passing through the cornea and lens, is not fully absorbed, but is reflected and returned back by a thin beam of light. It is this feature of the structure of the eyes of felines that allows them to see excellently in the dark.
The color of the glow may vary depending on the pigment located in the tapetum:
- green;
- yellow;
- bluish;
- at Siamese cats it is crimson in color.
A cat's eyes are 7 times superior to human eyes in their ability to discern images in the dark. People may also experience a faint red glow. This is clearly noticeable when photographing using a bright flash.
Why is this necessary?
The cat's glow-in-the-dark eyes provide signal amplification and improved image quality in the dark. This is explained by the fact that a weak ray of light penetrates the retina, is reflected from the tapetum and re-enters the retina, but now enhancing the signal and improving the visibility of the picture.
It is thanks to the built-in amplifier that cats perfectly distinguish objects even in the light of the stars. This allows them to be nocturnal and accurately strike in conditions of almost complete darkness by human standards. A cat is able to see the movement of objects from seven hundred meters away and can distinguish them perfectly from a distance of one to 57 meters.
In the dark, a cat’s eyes glow and at the same time can not blink thanks to the existing third eyelid. It does protective functions and prevents the eye from drying out, which is achieved by moving fluid.
The human eye responds to bright lighting by making the pupils very narrow (they narrow). In cats, the pupils transform into long narrow slits. This property allows the animal to regulate the amount of light that enters the organs of vision. It is the ability to control the intensity of light that distinguishes cats from other animals.
Previously, there was a hypothesis that cats see all objects as gray. The basis for this conclusion was that this is not necessary, because in the dark all images look in shades of gray. It is now a scientifically proven fact that cats distinguish the color spectrum, but much worse than humans.
Noticing a cat's eyes burning in the dark, a person sees only the reflection of a beam of light reflected from the tapetum.
Who posted
Site administration
