Goat pupil. Why do goats and sheep have rectangular pupils? Unusual pupil shape

And swooning goats competing for attention can't divert attention from what goats' eyes are like. Their horizontal, rectangular pupils seem alien compared to the round pupils of humans and dogs and the vertical pupils of cats. Why do goat eyes look like this? And for that matter, why do cat eyes look the way they do?

In a new study, Martin Banks, a vision scientist, found that the shape of an animal's pupils is the key to its place in the food chain . Banks and his team examined the eyes of 214 various kinds land animals and found a clear relationship between the shape of their pupils and their ecological role.In predatory animals that ambush their prey, as a rule, vertical section pupil, while herbivores, which are prey for other animals, have horizontal pupils.The pupil-predator separation suggests that both hunters and hunted individuals derive some benefit from a specific pupil type.

To find out what those benefits might be, the researchers analyzed the abilities of the two pupil shapes and how they might serve the different visual needs of predators and prey. Goats and other herbivores (e.g. deer, large cattle and elk) that are hunted by predators have a fairly simple strategy for avoiding being eaten: pay attention to danger and run if they see it.

To support such a strategy, their eyes must be able to do two things. “On the one hand, these animals must have panoramic vision in order to detect predators that may approach from different directions," the researchers wrote. “On the other hand, they need to see clearly enough in a straight line to move quickly over potentially uneven terrain.”

Horizontal pupils help here because their shape creates a sharp panoramic view that is wider and shorter than what others get with round or vertical pupils, and such a pupil allows the animal to see almost everything around it. A long horizontal pupil also improves the image quality of objects in front of and behind the animal, and helps the eye capture more light along the surface and less dazzling light overhead.

Of course, these advantages do not work if the pupil remains directed in the same way and becomes vertical when the animal tilts its head to graze. However, after observing grazing animals at the zoo, the researchers found that their eyes rotate in such a way as to remain horizontally aligned when their heads are held upright.

The researchers say that a long horizontal pupil seems ideal for these animals. In other words, goats strange eyes because they help them survive.

At the same time, the research team found that vertical, slit-like pupils help small predators such as squirrels to ambush and judge the distance to prey and other objects so they know how far they should jump.

“For those species that are active both day and night (for example, domestic cats), the incision of the pupils provides dynamic range necessary to help them see in dim light and not go blind in the midday sun," Martin Banks said in a statement. “However, this hypothesis does not explain why the cuts are placed vertically or horizontally. Why don't we see diagonal cuts? This study is the first attempt to explain this."

Round pupils, such as those of humans (or those of adult cats), tend to belong to predators. The eyes, which are slanted on the sides, like those of goats, belong to animals that graze in the pasture and are prey. Using computer models, the researchers confirmed that lateral eyes produce a much wider field of vision than eyes like ours.

Researchers say that next accent will be made by them on the study of the shape of the pupil of animals that live in water. This will be much more difficult, since the lateral position of the eyes of a sea creature, such as an octopus, for example, may indicate it as a predator and as a prey.

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Scientists have concluded that the visual system in animals began to develop approximately 540 million years ago. At first it had a simple structure, but over time it became more complex and improved for each type of vision. So, for example, fish see remarkably underwater, eagles with great height they will easily notice a small rodent on the ground, and cats are perfectly oriented in the dark.

Take a look at a selection of the most unusual eyes animals and see the uniqueness and wisdom of mother nature!

1. Mountain goat.
We are used to the fact that the human pupil has round shape. But in most ungulates, in particular the mountain goat, it has rectangular shape.

2. This pupil shape and horizontal vision is the best for mountain survival. So, without turning his head, the goat sees around him at 320-340 degrees. For comparison, a person sees only 160-200 degrees. Animals with such an eye structure see remarkably at night.

3. Trilobite.
Long before the advent of dinosaurs, the entire Earth was inhabited by marine arthropods, trilobites. Paleontologists have counted about 10,000 species of these animals. This class is now extinct.

4. Some representatives of this class were eyeless, but the majority had eyes that were unique in their structure. eye lens they consisted of calcite. It is a transparent mineral that is the basis of chalk and lime.
The shell of the eyes of modern invertebrates consists of chitin, a hard translucent substance. Unusual composition the eye gave these arthropods the ability to simultaneously keep in focus objects in the near and far distance. The vision of trilobites was either horizontal or vertical. But regardless of this, the animal saw only at a distance of approximately equal to the length own body.

Depending on the habitat, the eyes of trilobites were located either on elongated eyelids or covered with an eye cover that protected from the bright sun. Paleontologists have studied the vision of trilobites very thoroughly, as calcite fossils are well preserved.

5. Tarsiers.
Tarsiers are primates only 9-16 cm tall and weighing only 80-150 grams, living on the islands South-East Asia. The small size does not prevent the animal from being a predator at all. Moreover, tarsiers are the only primates in the world that eat only food of animal origin. They deftly catch lizards, insects and can even catch a bird during its flight. But their most important feature is their large glowing eyes in the dark. Their diameter can reach 16 mm. In relation to body size, these are the largest eyes among all known mammals.

6. Locals are still sure that tarsier is a messenger of evil spirits. And European tourists, when they first see such a baby, shudder and then remember this meeting for a long time. Imagine you are huge glowing eyes on a small round head. A second, and you are already looking at the back of the animal's head. He just turned his head...almost 360 degrees. Is it really impressive?

In addition, tarsiers have excellent night vision. Based on this, scientists conclude that animals recognize ultraviolet light.

7. Chameleon.
Many people know that the chameleon is able to change color. So he disguises himself and shows his mood and requirements to other lizards. The vision of these animals is also unusual - tightly fused eyelids cover everything. eyeball leaving only a small opening for the pupil.

The eyes of these lizards seem to fall out of their sockets and can rotate 360 ​​degrees independently of each other.

8. The eyes of a chameleon look in one direction only when its gaze is fixed on the prey. The lizard feeds on insects and small rodents. The chameleon notices its prey at a distance of several meters. Like the tarsier, it can see ultraviolet light.

9. Dragonfly.
The organs of vision of a dragonfly are also unique and unusual. They occupy almost the entire head of the insect and are able to cover the space 360 ​​degrees.

Each eye of a dragonfly is made up of 30,000 tiny photosensitive cells. In addition to two huge eyes, she has 3 more small eyes. Such a special vision makes the insect a dangerous aerial predator, capable of responding to any movement in just a split second.

10. There are also dragonflies that successfully hunt at dusk. Under these conditions, a person is not able to see much.

11. Leaf-tailed gecko.
Very unusual geckos live in the tropics of Madagascar. It is very difficult to notice them, because the shape and color of this animal is very similar to a dry leaf of a plant. For their large red eyes, these reptiles have received such names as "satanic" and "fantastic" geckos. The vision of these lizards has high sensitivity. Geckos are nocturnal animals. Even in total darkness they easily distinguish all objects and colors.

12. In comparison, cats see six times in dim light. better than a man. In the same conditions, geckos see 350 times better.

These reptiles owe such remarkable vision to the special structure of the pupil.

13. Colossal squid - the mystery of the ocean.
It is the largest invertebrate known to scientists. He is also the owner of the most big eyes among all representatives of the animal world. The diameter of his eye can reach 30 cm, and the pupil is the size of a large apple. The vision of squids is simply 100 percent even in dim light. This is very important for him, because these animals live at a depth of at least 2000 meters.

14. But besides this, the eyes of these squids have a built-in "spotlight" that turns on in the dark and gives required amount lights for successful hunting

15. Four-eyed fish.
This is a small fish up to 30 cm long, living in the waters of Mexico and South America. Its main food is insects, so it can often be seen on the water surface.

16. Despite the name, the fish has only two eyes. But they are divided by the flesh into four parts. Each part has its own lens.
The upper part of the eyes is adapted for vision in the air, the lower part for underwater observation.

17. Stalk-eyed fly.
Another unusual representative of the animal world. It got its name because of the thin long stem-like outgrowths on the sides of the head. At the ends of the stems are the eyes.
Males and females have different eye stalks in length and thickness. Females choose males with the longest stems.

18. During the mating season, males are measured by stems. To win, they even go to the trick - they inflate their eyes and stems with air, which increases their size and, of course, the chances of a female they like.

19. Dolichopteryx longipes.
This is a small deep-sea fish up to 18 cm long.

20. Only dolichopteryx has unique mirror vision. Her organs of vision work on the principle of a lens, and allow a small predator to see both surface and underwater space at the same time.

21. Spiders - ogres.
These are six-eyed spiders. But the middle pair of eyes they have is much larger than the rest, so it seems that the spiders are two-eyed.
Ogres are nocturnal predators. The spider's eyes are covered with a membrane of ultra-sensitive cells, providing excellent night vision.

22. Scientists believe that these spiders navigate in the dark at least a hundred times better than humans.

23. Crayfish - praying mantises.
These are the most dangerous representatives of arthropods in tropical waters. With their sharp claws, they can easily leave a person without fingers. They are the owners of the most unique eyes in the world.

Their eye consists of 10,000 supersensitive cells. Each of the cells performs a strictly defined function. For example, some are responsible for determining light, others are colors. This type crayfish captures shades of colors 4 times better than humans.

They are the only ones with ultraviolet, infrared and polar vision at the same time. In addition, their eyes can rotate 70 degrees. It is also surprising that the information received from these cancers is processed not by the brain, but by the eyes.

24. But that's not all. These crayfish have "trinocular vision". Cancer's eye is divided into three parts, and he can see everything that happens from 3 different points of the same eye.
This is the most unique structure of the visual system. Scientists are still unable to fully explain it, let alone recreate it. We can only marvel at the wisdom and originality of nature.

The veterinary ophthalmologist, microsurgeon, Ph.D. Konstantin Perepechaev

The pupil is, in fact, the diaphragm, which, narrowing or expanding, regulates the flow of light to the retina of the eye. In addition, its size and shape affect the field of view and the quality of the image obtained on the retina. In different animals - depending on the ecological niches they occupy, their location in the food chain, lifestyle and type of nutrition - these characteristics differ from each other.

Herbivorous ungulates (goats, sheep, cows, antelopes, horses, etc.) in the food chain are always victims of any predators. In accordance with this, they visual analyzer forms visual information, and the brain processes it in terms of "prey mentality" (prey mentality). Any fast-moving object, even if it is not clearly visible, may well be an attacking predator, so any unexpected movement immediately causes the herbivore to defensive reflex: defense and/or flight.

All herbivores have large eyes, slightly protruding, located almost on the sides of the head. This provides the widest field of view. For example, overall width The horse's visual field is approximately 350º. Thus, the horse does not see only a narrow sector immediately behind the poll. (In the article "My Planet" you can read and even watch how a horse, a bee, a cat, etc. see the world.)

AT daytime in strong light, the eyes of goats and sheep look like a narrow slit; in the dark, the pupil expands, taking the form of rectangles or even squares. The long horizontal pupil enhances the image of objects in front of and behind the animal, making it easier to move quickly over uneven or mountainous terrain.

The rectangular, or rather, horizontally oval pupil in herbivores just helps to see the widest possible panoramic picture around them. Due to the stretched shape of the pupil, a goat, for example, has a viewing angle of almost 340 °, that is, when grazing, it calmly observes what is happening around it, without even raising its head. In the daytime, with strong illumination, the eyes of goats and sheep look like a narrow slit; in the dark, the pupil expands, taking the form of rectangles or even squares. Such a mechanism contributes to all the same - better view during the dark hours of the day. A goat, like other animals with such pupils, is able to notice a moving predator almost behind itself at night. When a predator appears in the field of view of at least one of the goats, the entire herd will have time to escape.

According to latest research, a long horizontal pupil also enhances the image of objects in front of and behind the animal, making it easier to move quickly over uneven or mountainous terrain, as well as helping the eye capture more light along the surface and less blinding light overhead. In addition, when observing grazing animals in a zoo, the researchers found that the animals' eyes rotate in such a way that the line of pupils always remains horizontally aligned, even when the animals' heads are lowered vertically down.

The shape of the pupils of animals is predominantly rounded, but there are enough exceptions. One of these representatives is among artiodactyls - this is a goat (goat). She has rectangular pupils, deployed horizontally. In bright light, they narrow down to the formation of a line, and in the dark, they expand to a maximum. The latter determines the origin of the expression "bug-eyed goat".

At a large number hoofed pupils have a rectangular shape. We exclude the giraffe.

Who else

We list other animals endowed by nature with rectangular pupils:

• cow, horse, llama, hippopotamus, mongoose, octopus;
• a sheep (ram) is a relative relative to a goat, which determines the shape of the pupils under consideration;
• shark, stingray - looks like a rectangle with vertical arrangement. Found in some species;
• gecko - to a lesser extent resembles a regular rectangle, but the shape is elongated, which allows it to be included in the list. Not all representatives of this family of lizards have such pupils;
• amphibian (aka frog) - depending on the type of amphibian, the pupils are located horizontally or vertically.

Why are pupils rectangular?

The explanation here is simple. Let's take a goat for example. She needs to constantly receive food - she grazes. Previously, goats were wild and hunted by other animals. In this regard, it became necessary to survey the surroundings without taking your head off the ground. This led to the expansion of the pupils horizontally. The viewing angle began to reach 340 degrees without turning the head.

The same explanation is suitable for other representatives of the animal world with rectangular pupils.