A Tree snake.
Environment | Wildlife

Can snakes See Us As We See Them?

Afraid of snakes? You know nothing about them

Snakes are always scary creatures for people in general. It is because the world has been depicting snakes as a symbol of devil from the time immemorial. In fact, out of more than 3500 species of snakes reported from this planet, only a small percent (~600 numbers) are venomous. And, among these, deadly venomous snakes are only a few. However, those who don’t know much about snakes will consider all of them equally dangerous. Also, there are many misconceptions and stories spread about them which make people scared. For example, an indigenous group in Kerala believes that if our shadow falls on a basking King Cobra, it will follow and attack that particular person when it gets an opportunity! The question here is, can snakes see us? if yes, how? How well they can see us and observe our movements?

An indigenous group in Kerala believes that if our shadow falls on a basking King Cobra, it will follow and attack us when it gets an opportunity!

Can snakes see? Know, how snakes’ eyes work

We always wonder whether snakes can see us clearly. Can they hear our voice? If not, how they are moving (or dancing!) when snake charmers play the music?
A study led by scientists and vision experts from Natural History Museum, London revealed that most snakes have three visual pigments. Among these three, two are in cone that enable them to see two primary colors. Remember, we humans can see three primary colors. Scientists also found that some snake species are very sensitive to Ultraviolet (UV) light that allows them to see objects even in low light conditions based on their lifestyles.

The snakes that hunt during daytime have eyes that can block UV light and help them see clearly in bright light conditions. But, those species hunt in night have eyes that allow more UV light which makes them more efficient in low light conditions.

A burrowing snake (Bhupathy’s shieldtail, Uropeltis bhupathyi) with poorly developed eyes
A burrowing snake (Bhupathy’s shieldtail, Uropeltis bhupathyi) with poorly developed eyes. Copyright. Jins V.J.

Can snakes hear the charmer’s music?

Snakes can detect the vibrations on the ground and some low-frequency airborne waves with the help of their inner auditory system

The snake charmer can make a cobra dance only because of the movement of his instrument (Pungi) not because of the music he plays. Snakes simply move by looking at the Pungi and by sensing the direction of the charmer’s hand as a defensive strategy towards the threat. Since snakes do not have an outer ear, they cannot hear music. But, they can detect the vibrations on the ground and some low-frequency airborne waves with the help of their inner auditory system. This is how a snake can run away from us even before we reach close to them.

Evolutionary significance of snakes’ eyesight

A nocturnal species (Ceylon Cat Snake, Boiga ceylonensis) with a vertical pupil like a cat
A nocturnal species (Ceylon Cat Snake, Boiga ceylonensis) with a vertical pupil like a cat. Adapted for night hunting. Copyright. Jins V.J.

Most of the studies on the molecular basis of vision were performed on mammals, birds, and fishes. But studying snakes’ vision will help us understand how vision functions have evolved in vertebrates more generally‘; Dr. David Gower from Natural History museum says. Reptiles are the first group of vertebrates that evolved to live entirely in terrestrial conditions. They are very much diverse in their life histories, behavior, and body shapes compared to any other vertebrate taxa. Based on their lifestyle and habitat conditions, they have developed different kinds of vision functions and abilities.

Can snakes see? Evidence of evolution speaks

Tree snakes have well-developed eyes that help them to see their prey or predator from a fairly long distance clearly.

The evidence from various studies indicates that snakes’ eyes adapt to living in low light conditions in land. Snakes are the limbless reptiles that are adapted to live in a wide variety of microhabitats from underground soil to the top of a tree. The species that live under the soil (burrowing snakes) has poorly developed eyes. However, tree snakes have well-developed eyes that help them to see their prey or predator from a fairly long distance clearly.

Since the burrowing snakes spend most of their life under the soil, vision becomes less important for them. Snakes that ambush their prey and hunt at night tend to have vertical pupils like that of a cat that can enhance night vision. But, diurnal species (those who are active during the day) mostly have round pupils. A study conducted in Australia on the shapes of the pupil in snakes revealed that round and vertical pupils evolved in snakes based on their hunting behavior. Narrow vertical pupil helps a snake to project a sharper image into its retina.

More ways for snakes to detect prey or predator

Apart from their visual abilities, some snakes like Vipers, Boas, and Pythons can identify the presence of prey or predator by detecting infrared radiations, using their pit organs. Pit organs are a pair of holes in their faces which can detect infrared radiations from warm bodies even from one meter or more distance. The molecular heat detectors and nerve fibers of pit organs help snakes to form a thermal profile. And, at night, these organs can work like an infrared camera allowing snakes to see their prey or predator as thermal images.

Also, we see that snakes flick their bifurcated tongues in the air when they get vibrations of our movement. It picks up chemical particles from the air, and once it puts its tongue back, a special organ called Jacobson’s organ sense these particles. Jacobson’s organ situates on the roof of their mouth. With this sense of smell, they can detect the presence of their approaching prey or predator.

The large-scaled pit viper, Trimeresurus macrolepis has pit organs (hole between nostril and eye) that can detect infrared radiations. Arboreal and nocturnal.
The large-scaled pit viper, Trimeresurus macrolepis has pit organs (hole between nostril and eye) that can detect infrared radiations. Arboreal and nocturnal. Copyright. Jins V.J.

How do you see snakes? An annoying question

Now we know how snakes see us. But, it is also important to think about how human beings look at them. We often perceive them as dangerous or useless animals which are a threat to our life. Due to this misconception, the first thing people do when they encounter a snake is to kill it. Firstly, we need to realize that all snakes are not venomous. Although we have about 300 species of snakes in India, major death cases due to snakebite in the country occur from four or five species only.

Although we have about 300 species of snakes in India, major death cases due to snakebite occur from four or five species only

Undoubtedly, snakes are important elements in every ecosystem as they regulate the populations of their prey. In agricultural fields, snakes feed on rats and other pests and maintain the balance of the system. Snakes are an essential part of sustainable farming. Being ectothermic organisms (those who use external energy for their body metabolism), snakes are under serious threat by global climate change and local changes in temperature. Habitat destructions and the use of pesticides in agricultural fields will also harm many species of snakes.

Hence, it is our responsibility to understand their life better and change the way we look at them. Protecting their habitats and boosting our knowledge about snakes is the most important things that we can do for their conservation.

For more reading:

  1. Simões, B. F., Sampaio, F. L., Douglas, R. H., Kodandaramaiah, U., Casewell, N. R., Harrison, R. A., … & Gower, D. J. (2016). Visual pigments, ocular filters and the evolution of snake vision. Molecular biology and evolution, 33(10), 2483-2495.
  2. Fang, J. (2010). Snake infrared detection unravelled. Nature, doi:10.1038/news.2010.122 . Retrieved from https://www.nature.com/news/2010/100314/full/news.2010.122.html

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10 Comments

  1. Hi Jins,
    I wonder how one could explain such difficult scientific aspects in such a simple way. I normally skip articles written on such subjects as they are beyond my level of comprehension. But, this one was something unique for its readability and preciseness. Expecting more from you.

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