What sense organ does a snake use to detect another animal? Snake vision. Infrared vision organs of snakes

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Scientists have been observing the behavior of snakes for quite some time. The main organs for reading information are thermal sensitivity and smell.

The sense of smell is the main organ. The snake constantly works with its forked tongue, taking samples of air, soil, water and objects surrounding the snake.

Thermal sensitivity. A unique sensory organ that snakes have. allows you to “see” mammals while hunting even in complete darkness. In the viper, these are sensory receptors located in deep grooves on the muzzle. A snake like a rattlesnake has two large spots on its head. Rattlesnake not only sees warm-blooded prey, it knows the distance to it and the direction of movement.
The snake's eyes are covered with completely fused transparent eyelids. Vision different types The snake may vary, but serves primarily to track the movement of prey.

All this is interesting, but what about hearing?

It is absolutely known that snakes do not have hearing organs in the usual sense. The eardrum, auditory ossicles and cochlea, which transmit sound through nerve fibers to the brain, are completely absent.

However, snakes can hear, or rather feel, the presence of other animals. The sensation is transmitted through vibrations of the soil. This is how reptiles hunt and hide from danger. This ability to perceive danger is called vibration sensitivity. The vibration of the snake is felt by the whole body. Even very low sound frequencies are transmitted to the snake through vibration.

Quite recently, a sensational article appeared by zoologists from the Danish University of Aarhus (Aarhus University, Denmark) who studied the effect on the neurons of the python’s brain from a speaker turned on in the air. It turned out that the basics of hearing are present in the experimental python: there is an inner and outer ear, but there is no eardrum - the signal is transmitted directly to the skull. It was even possible to record the frequencies “heard” by the python bones: 80-160 Hz. This is an extremely narrow low-frequency range. Man is known to hear 16-20000 Hz. However, whether other snakes have similar abilities is not yet known.

The organs that allow snakes to “see” thermal radiation provide an extremely blurry image. Nevertheless, the snake forms a clear thermal picture of the surrounding world in its brain. German researchers have figured out how this can be.

Some species of snakes have unique ability capture thermal radiation, allowing them to “look” the world in absolute darkness. True, they “see” thermal radiation not with their eyes, but with special heat-sensitive organs (see figure).

The structure of such an organ is very simple. Next to each eye is a hole about a millimeter in diameter, which leads into a small cavity of approximately the same size. On the walls of the cavity there is a membrane containing a matrix of thermoreceptor cells measuring approximately 40 by 40 cells. Unlike the rods and cones of the retina, these cells respond not to the “brightness of light” of heat rays, but to local temperature membranes.

This organ works like a camera obscura, a prototype of cameras. A small warm-blooded animal against a cold background emits “heat rays” in all directions - far infrared radiation with a wavelength of approximately 10 microns. Passing through the hole, these rays locally heat the membrane and create a “thermal image”. Thanks to the highest sensitivity of receptor cells (temperature differences of thousandths of a degree Celsius are detected!) and good angular resolution, a snake can notice a mouse in absolute darkness from a fairly long distance.

From a physics point of view, it is precisely good angular resolution that poses a mystery. Nature has optimized this organ so as to better “see” even weak sources of heat, that is, it has simply increased the size of the inlet - the aperture. But the larger the aperture, the more blurry the image turns out (we are talking, we emphasize, about the most ordinary hole, without any lenses). In a snake situation, where the camera aperture and depth are approximately equal, the image is so blurry that nothing more than “there is a warm-blooded animal somewhere nearby” can be extracted from it. However, experiments with snakes show that they can determine the direction of a point source of heat with an accuracy of about 5 degrees! How do snakes manage to achieve such high spatial resolution with such terrible quality of “infrared optics”?

Since the real “thermal image,” the authors say, is very blurry, and the “spatial picture” that arises in the animal’s brain is quite clear, it means that there is some kind of intermediate neural apparatus on the way from the receptors to the brain, which, as it were, adjusts the sharpness of the image. This apparatus should not be too complex, otherwise the snake would “think about” each image received for a very long time and would react to stimuli with a delay. Moreover, according to the authors, this device is unlikely to use multi-stage iterative mappings, but is, rather, some kind of fast one-step converter that works according to a permanently hardwired nervous system program.

In their work, the researchers proved that such a procedure is possible and quite realistic. They carried out mathematical modeling of how a “thermal image” occurs and developed an optimal algorithm for repeatedly improving its clarity, dubbing it a “virtual lens.”

Despite big name, the approach they used, of course, is not something fundamentally new, but just a type of deconvolution - restoration of an image spoiled by the imperfection of the detector. This is the reverse of image blurring and is widely used in computer image processing.

There was, however, an important nuance in the analysis: the deconvolution law did not need to be guessed; it could be calculated based on the geometry of the sensitive cavity. In other words, it was known in advance what specific image a point source of light in any direction would produce. Thanks to this, a completely blurred image could be restored with very good accuracy (ordinary graphic editors with a standard deconvolution law would not have been able to cope even close to this task). The authors also proposed a specific neurophysiological implementation of this transformation.

Whether this work said any new word in the theory of image processing is a moot point. However, it certainly led to unexpected findings regarding the neurophysiology of “infrared vision” in snakes. Indeed, the local mechanism of “ordinary” vision (each visual neuron takes information from its own small area on the retina) seems so natural that it is difficult to imagine something very different. But if snakes really use the described deconvolution procedure, then each neuron that contributes to the whole picture of the surrounding world in the brain receives data not from a point at all, but from a whole ring of receptors running across the entire membrane. One can only wonder how nature managed to construct such “nonlocal vision”, which compensates for the defects of infrared optics with non-trivial mathematical transformations of the signal.

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For some reason, it seems to me that the reverse transformation of a blurry image, provided that there is only a two-dimensional array of pixels, is mathematically impossible. As far as I understand, computer sharpening algorithms simply create the subjective illusion of a sharper image, but they cannot reveal what is blurred in the image.

Is not it?

In addition, the logic from which it follows that a complex algorithm would force a snake to think is incomprehensible. As far as I know, the brain is a parallel computer. A complex algorithm in it does not necessarily lead to an increase in time costs.

It seems to me that the refinement process should be different. How was the accuracy of the work determined? infrared eyes? Probably due to some action of the snake. But any action is long-lasting and allows for correction in its process. In my opinion, a snake can "infrasee" with the accuracy that is expected and begin to move based on this information. But then, in the process of movement, constantly refine it and come to the end as if the overall accuracy was higher.

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• I answer point by point.

  1. Inverse transformation is the production of a sharp image (as an object with a lens such as an eye would create) based on the existing blurry one. Moreover, both pictures are two-dimensional, there are no problems with this. If there are no irreversible distortions during blur (such as a completely opaque screen or signal saturation in some pixel), then blur can be thought of as a reversible operator operating in the space of two-dimensional images.

  There is technical difficulties taking into account noise, so the deconvolution operator looks a little more complicated than described above, but nevertheless is derived unambiguously.

  2. Computer algorithms improve sharpness, assuming that the blur was Gaussian. They don’t know in detail the aberrations, etc., that the camera that was filming had. Special programs However, they are capable of more. For example, if, when analyzing images of the starry sky
  If a star enters the frame, then with its help you can restore sharpness better than with standard methods.

  3. Complex processing algorithm - this meant multi-stage. In principle, images can be processed iteratively, running the image along the same simple chain over and over again. Asymptotically, it can then converge towards some “ideal” image. So, the authors show that such processing, at least, is not necessary.

  4. I don’t know the details of experiments with snakes, I’ll have to read it.

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  • 1. I didn't know this. It seemed to me that blur (insufficient sharpness) was an irreversible transformation. Let's say there is objectively some blurry cloud in the image. How does the system know that this cloud should not be sharpened and that this is its true state?

    3. In my opinion, iterative transformation can be implemented by simply making several sequentially connected layers of neurons, and then the transformation will take place in one step, but be iterative. How many iterations are needed, so many layers to make.

    Answer

    • Here's a simple example of blur. Given a set of values ​​(x1,x2,x3,x4).
      The eye sees not this set, but the set (y1,y2,y3,y4), resulting in this way:
      y1 = x1 + x2
      y2 = x1 + x2 + x3
      y3 = x2 + x3 + x4
      y4 = x3 + x4

      Obviously, if you know the blurring law in advance, i.e. linear operator(matrix) of transition from X's to Y's, then you can count inverse matrix transition (the law of deconvolution) and, based on the given players, restore the X's. If, of course, the matrix is ​​invertible, i.e. there are no irreversible distortions.

      About several layers - of course, this option cannot be dismissed, but it seems so uneconomical and so easily broken that one can hardly expect that evolution will choose this path.

      Answer

      "Obviously, if you know in advance the law of blurring, i.e. the linear operator (matrix) of transition from X's to Y's, then you can calculate the inverse transition matrix (deconvolution law) and restore the X's from the given Y's. If, of course, the matrix is ​​invertible, i.e. there are no irreversible distortions." Don't confuse math with measurements. Masking the lowest charge with errors is non-linear enough to spoil the result of the reverse operation.

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“3. In my opinion, an iterative transformation can be implemented by simply making several sequentially connected layers of neurons, and then the transformation will take place in one step, but be iterative. How many iterations are needed, so many layers can be made.” No. The next layer begins processing AFTER the previous one. The conveyor does not allow speeding up the processing of a specific piece of information, except in cases when it is used to entrust each operation to a specialized performer. It allows you to start processing the NEXT FRAME before the previous one is processed.

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"1. Inverse transformation is the sharp production of a picture (which would be created by an object with a lens like an eye) based on the existing blurred one. Moreover, both pictures are two-dimensional, there are no problems with this. If there are no irreversible distortions during blur (such as completely opaque screen or signal saturation in some pixel), then blur can be thought of as a reversible operator operating in the space of two-dimensional pictures." No. Blurring is a reduction in the amount of information; it is impossible to create it again. You can increase the contrast, but if this does not come down to adjusting the gamma, then only at the cost of noise. When blurring, any pixel is averaged over its neighbors. FROM ALL SIDES. After this, it is not known where exactly something was added to its brightness. Either from the left, or from the right, or from above, or from below, or diagonally. Yes, the direction of the gradient tells us where the main additive came from. There is exactly as much information in this as in the most blurry picture. That is, the resolution is low. And little things are only better masked by noise.

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It seems to me that the authors of the experiment simply “produced unnecessary entities.” Is there absolute darkness in the real habitat of snakes? - as far as I know, no. And if there is no absolute darkness, then even the most blurry “infrared picture” is more than enough, its entire “function” is to give the command to start hunting “approximately in such and such a direction,” and then the most ordinary vision comes into play. The authors of the experiment refer to the too high accuracy of the choice of direction - 5 degrees. But is this really great accuracy? In my opinion, under no conditions - neither in a real environment nor in a laboratory - will a hunt be successful with such “precision” (if the snake is oriented only in this way). If we talk about the impossibility of even such “accuracy” due to the too primitive processing device infrared radiation, then, apparently, one can disagree with the Germans: the snake has two such “devices”, and this gives it the opportunity to “on the fly” determine “right”, “left” and “straight” with further constant correction of direction up to until the moment of "visual contact". But even if the snake has only one such “device”, then in this case it will easily determine the direction - by the temperature difference in different parts of the “membrane” (it’s not for nothing that it detects changes in thousandths of a degree Celsius, for which - then this is necessary!) Obviously, an object located “directly” will be “displayed” by a picture of more or less equal intensity, one located “on the left” - by a picture with greater intensity of the right “part”, and located “on the right” - by a picture with greater intensity of the left part. That's all. And there is no need for any complex German innovations in the snake nature that has developed over millions of years :)

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“It seems to me that the precision process should be different. How was the accuracy of the infrared eyes established? Surely, by some action of the snake. But any action is long-lasting and allows for correction in its process. In my opinion, a snake can “infra-see” with that accuracy, which is expected and start moving based on this information. But then, in the process of movement, constantly refine it and come to the end as if the overall accuracy was higher." But the mixture of a balometer with a light-recording matrix is ​​already very inertial, and the heat of the mouse frankly slows it down. And the snake’s throw is so fast that cone and rod vision cannot keep up. Well, maybe it’s not the fault of the cones themselves, where the accommodation of the lens slows down and processing. But even the whole system works faster and still can’t keep up. The only thing Possible Solution with such sensors, all decisions are made in advance, using the fact that there is enough time before the throw.

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“In addition, the logic from which it follows that a complex algorithm would make a snake think is incomprehensible. As far as I know, the brain is a parallel computer. A complex algorithm in it does not necessarily lead to an increase in time costs.” To parallelize a complex algorithm, you need many nodes; they are of decent size and slow down due to the slow passage of signals. Yes, this is not a reason to abandon parallelism, but if the requirements are very strict, then the only way to meet the deadline when processing large arrays in parallel - use so many simple nodes that they cannot exchange intermediate results with each other. And this requires hardening the entire algorithm, since they will no longer be able to make decisions. And it will also be possible to process a lot of information sequentially in the only case - if the only processor works quickly. And this also requires hardening the algorithm. The level of implementation is hard and so on.

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>German researchers have figured out how this can be.

but the cart, it seems, is still there.
You can immediately propose a couple of algorithms that may solve the issue. But will they be relevant to reality?

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• > I would like at least indirect confirmation that it is exactly like this and not otherwise.

  Of course, the authors are careful in their statements and do not say that they have proven that this is exactly how infravision functions in snakes. They only proved that resolving the “infravision paradox” does not require too much computing resources. They only hope that the organ of snakes works in a similar way. Whether this is true or not must be proven by physiologists.

  Answer

  > There is a so-called binding problem, which is how a person and an animal understand that sensations in different modalities (vision, hearing, heat, etc.) refer to the same source.

  In my opinion, there is a holistic model in the brain real world, rather than individual shard-modalities. For example, in the brain of an owl there is an object “mouse”, which has, as it were, corresponding fields that store information about what the mouse looks like, how it sounds, how it smells, and so on. During perception, stimuli are converted into terms of this model, that is, a “mouse” object is created, its fields are filled with squeaks and appearance.

  That is, the question is posed not as to how the owl understands that both the squeak and the smell belong to the same source, but how the owl CORRECTLY understands individual signals?

  Recognition method. Even signals of the same modality are not so easy to assign to the same object. For example, a mouse tail and mouse ears could well be individual items. But the owl does not see them separately, but as parts of a whole mouse. The thing is that she has a prototype of a mouse in her head, with which she matches the parts. If the parts “fit” onto the prototype, then they make up the whole; if they don’t fit, then they don’t.

  It's easy to understand at by example. Consider the word "RECOGNITION". Let's look at it carefully. In fact, it's just a collection of letters. Even just a collection of pixels. But we can't see it. The word is familiar to us and therefore the combination of letters inevitably evokes a solid image in our brain, which is simply impossible to get rid of.

  So is the owl. She sees the tail, she sees the ears, approximately in a certain direction. Sees characteristic movements. He hears rustling and squeaking from approximately the same direction. Feels a special smell from that side. And this familiar combination of stimuli, just like a familiar combination of letters for us, evokes the image of a mouse in her brain. The image is integral, located in the integral image of the surrounding space. The image exists independently and, as the owl observes, can be greatly refined.

  I think the same thing happens with a snake. And how in such a situation it is possible to calculate the accuracy of just a visual or infrasensory analyzer is not clear to me.

  Answer

  • It seems to me that recognizing an image is a different process. It's about not about the reaction of a snake to the image of a mouse, but about the transformation of spots in the infra-eye into the image of a mouse. Theoretically, one can imagine a situation where the snake does not infrasee the mouse at all, but immediately rushes in a certain direction if its infra-eye sees ring circles a certain shape. But this seems unlikely. After all, with ORDINARY eyes the earth sees precisely the profile of the mouse!

    Answer

    • It seems to me that the following may be happening. A poor image appears on the infraretina. It transforms into a vague image of a mouse, sufficient for the snake to recognize the mouse. But there is nothing “miraculous” in this image; it is adequate to the abilities of the infra-eye. The snake begins an approximate lunge. During the throw, her head moves, her infra-eye moves relative to the target and generally gets closer to it. The image in the head is constantly supplemented and its spatial position is clarified. And the movement is constantly being adjusted. As a result, the final throw looks as if the throw was based on incredibly accurate information about the target's position.

      This reminds me of watching myself, when sometimes I can catch a fallen glass just like a ninja :) And the secret is that I can only catch the glass that I myself dropped. That is, I know for sure that the glass will have to be caught and I start the movement in advance, correcting it in the process.

      I also read that similar conclusions were drawn from observations of a person in zero gravity. When a person presses a button in zero gravity, he must miss upward, since the forces usual for a weighing hand are incorrect for weightlessness. But a person does not miss (if he is attentive), precisely because the possibility of correction “on the fly” is constantly built into our movements.

      Answer

“There is a so-called binding problem, which is how a person and an animal understand that sensations in different modalities (vision, hearing, heat, etc.) refer to the same source.
There are many hypotheses http://www.dartmouth.edu/~adinar/publications/binding.pdf
but the cart, it seems, is still there.
You can immediately propose a couple of algorithms that may solve the issue. But will they be related to reality?" But this is similar. Do not react to cold leaves, no matter how they move or look, but if there is a warm mouse somewhere there, attack something that looks like a mouse in optics and this falls into the area. Or some kind of very wild processing is needed. Not in the sense of a long sequential algorithm, but in the sense of the ability to draw patterns on nails with a janitor's broom. Some Asians even know how to harden this so much that they manage to make billions of transistors. And that one too sensor.

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>in the brain there is a holistic model of the real world, and not separate fragments-modalities.
Here's another hypothesis.
Well, what about without a model? There is no way without a model. Of course, simple recognition in a familiar situation is also possible. But, for example, when first entering a workshop where thousands of machines operate, a person is able to single out the sound of one specific machine.
The trouble may be that different people use different algorithms. And even one person can use different algorithms in different situations. With snakes, by the way, this is also possible. True, this seditious thought may become a tombstone for statistical methods of research. What psychology cannot tolerate.

In my opinion, such speculative articles have a right to exist, but it is necessary to at least bring it to the design of an experiment to test the hypothesis. For example, based on the model, calculate the possible trajectories of the snake. Let physiologists compare them with real ones. If they understand what we're talking about.
Otherwise, there is a binding problem. When I read yet another unsupported hypothesis, it only makes me smile.

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• > Here is another hypothesis.
  Strange, I didn’t think this hypothesis was new.

  In any case, she has confirmation. For example, people with amputated limbs often claim that they continue to feel them. For example, good motorists claim that they “feel” the edges of their car, the location of the wheels, etc.

  This suggests that there is no difference between the two cases. In the first case, there is an innate model of your body, and sensations only fill it with content. When a limb is removed, the model of the limb still exists for some time and causes sensation. In the second case, there is a purchased car model. The body does not receive direct signals from the car, but indirect signals. But the result is the same: the model exists, is filled with content and is felt.

  Here, by the way, good example. Let's ask the motorist to run over a pebble. He will hit you very accurately and will even tell you whether he hit you or not. This means that he feels the wheel by vibrations. Does it follow from this that there is some kind of “virtual vibrating lens” algorithm that reconstructs the image of the wheel based on vibrations?

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It is quite curious that if there is only one light source, and quite strong, then the direction towards it is easy to determine even with your eyes closed - you need to turn your head until the light begins to shine equally in both eyes, and then the light is in front. There is no need to come up with some super-duper neural networks in image restoration - everything is simply terribly simple, and you can check it yourself.

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Reptile eyes indicate their way of life. In different species we observe a unique structure of the visual organs. To protect their eyes, some “cry”, others have eyelids, and still others “wear glasses”.
Reptile vision , like the diversity of species, is very different. How the eyes are positioned on a reptile's head largely determines how much the animal sees. When the eyes are set on both sides of the head, the visual fields of the eyes do not intersect. Such animals see well everything that happens on both sides of them, but their spatial vision is very limited (they cannot see the same object with both eyes). When a reptile's eyes are set at the front of its head, the animal can see the same object with both eyes. This position of the eyes helps reptiles more accurately determine the location of prey and the distance to it. IN land turtles and many lizards have eyes set on both sides of their heads, so they can clearly see everything that surrounds them. The snapping turtle has excellent spatial vision because its eyes are set at the front of its head. Chameleons' eyes, like cannons in defensive towers, can rotate independently 180° horizontally and 90° vertically - they can see behind them.

How do snakes exhibit their heat source?.
The most important sensory organ of a snake is the tongue in combination with Jacobson's organ. However, reptiles also have other adaptations necessary for successful hunting. To identify prey, snakes need more than just their eyes. Some snakes can sense heat emitted by the animal's body.
Pit-headed snakes, which include the true pit snakes, got their name due to the fact that they have a paired sensory organ in the form of facial pits located between the nostrils and the eye. With the help of this organ, snakes can sense warm-blooded animals by the difference in temperature between its body and the external environment with an accuracy of 0.2 ° C. The size of this organ is only a few millimeters, but it can detect infrared rays emitted by potential prey and transmit the received information through nerve endings in the brain. The brain perceives this information and analyzes it, so the snake has a clear idea of ​​what kind of prey it encountered on its way and where exactly it is located. Different kinds Reptiles see and perceive the world around them very differently. The field of vision, its expressiveness and the ability to distinguish colors depend on how the animal’s eyes are set, on the shape of the pupils, as well as on the number and type of light-sensitive cells. In reptiles, vision is also related to their lifestyle.
Color vision
Many of the lizards can perfectly distinguish colors, which for them is important means communication. Some of them recognize scarlet ones on a black background poisonous insects. In the retina of the eyes of diurnal lizards there are special elements of color vision - bulbs. Giant turtles distinguish colors, some of them respond particularly well to red light. They are even thought to be able to see infrared light, which the human eye cannot distinguish. Crocodiles and snakes are color blind.
American night lizards react not only to shape, but also to color. However, their retina still contains more rods than cones.
Reptile vision
The class of reptiles, or reptiles, includes crocodiles, alligators, turtles, snakes, geckos and lizards such as the hatteria. The reptile needs to receive accurate information about the size and color of its potential prey. In addition, the reptile must detect and quickly react when other animals approach and determine who it is - a potential partner, a young animal of the same species, or an enemy that may attack it. Reptiles that live underground or in water have rather small eyes. Those of them that live on earth depend more on visual acuity. The eyes of these animals are structured in the same way as human eyes. Their very part is the eyeball with the optic nerve. In front of it is the cornea, which allows light to pass through. The cornea is the iris. At its center is the pupil, which contracts or dilates, allowing a certain amount of light to pass onto the retina. Under the pupil there is a lens through which rays hit the light-sensitive back wall of the eyeball - the retina. The retina is made up of layers of light- and color-sensitive cells connected by the optic nerves to the brain, where all signals are sent and where an image of an object is created.
Eye protection
Some species of reptiles use eyelids to protect their eyes, just like mammals. However, reptile eyelids differ from mammalian eyelids in that the lower eyelid is larger and more mobile than the upper.
The snake's gaze appears glassy because its eyes are covered with a transparent film formed by the fused upper and lower eyelids. This protective coating is a kind of “glasses”. During molting, this film comes off along with the skin. Lizards also wear “glasses,” but only some. Geckos do not have eyelids. To clean their eyes, they use their tongue, sticking it out of their mouth and licking the eye shell. Other reptiles have a "parietal eye". This is a light spot on the head of a reptile; like a regular eye, it can perceive certain light stimuli and transmit signals to the brain. Some reptiles protect their eyes from pollution using lacrimal glands. When sand or other debris gets into the eyes of such reptiles, the lacrimal glands secrete a large number of a liquid that cleanses the animal's eyes, making the reptile appear to "cry". Soup turtles use this method.
Pupil structure

The pupils of reptiles indicate their lifestyle. Some of them, for example, crocodiles, pythons, geckos, hatteria, snakes, are nocturnal or twilight image life, and take sunbathing during the day. They have vertical pupils that dilate in the dark and constrict in light. In geckos, pinpoint holes are visible on the constricted pupils, each of which focuses an independent image onto the retina. Together they create the necessary sharpness, and the animal sees a clear image.

You can read interesting things about penguins on the website kvn201.com.ua.

Of all the many different animals living on Earth, the eyes of a snake are capable of distinguishing colors and shades. Vision for a snake plays a big role in life, although it is not the main sense for getting to know outside world. Snakes on our planet are about . As many people know from school, snakes belong to the order of squamates. Their habitat is areas with warm or temperate climate. .

How do snake eyes work?

The snake eye, unlike other animals, does not have visual acuity. This is because their eyes are covered with a thin leathery film, they are very cloudy, and this greatly affects visibility. During molting, the snake sheds its old skin, and along with it the film. Therefore, after molting, snakes are especially “big-eyed”. Their vision becomes sharper and clearer for several months. Because of the film on the eyes, people since ancient times have given the snake's gaze a special coldness and hypnotic power.

Most snakes living near humans are harmless and do not pose any danger to humans. But there are also poisonous ones. Snake venom is used for hunting and protection.

Depending on the way of hunting - in the daytime or at night, the shape of the pupil of snakes changes. For example, the pupil is round, and snakes that engage in twilight hunting have acquired vertical and elongated eyes with long slits.

But the most unusual eyes have the species of whip snakes. Their eye is very similar to a keyhole located horizontally. Because of this unusual structure of the eyes, the snake skillfully uses its binocular vision - that is, each eye forms a complete picture of the world.

But the main sense organ of snakes is still smell. This organ is the main one for thermolocation of vipers and pythons. The sense of smell allows one to sense the warmth of its victims in pitch darkness and quite accurately determine their location. Snakes that are non-venomous strangle or wrap their bodies around their prey, and there are also those that swallow their prey alive. Most snakes are small in size, no more than one meter. During a hunt, the snake's eyes focus on one point, and their forked tongue, thanks to the Jacobson's organ, tracks the subtlest odors in the air.