Does your reptile see the world the way we do?

Reptile vision holds a few surprises and can be quite different from our own.

UV perception, colours that remain visible even in very low light, eyes capable of looking in two different directions, or even the ability to detect heat in certain snakes… These abilities vary enormously from one species to another and are closely linked to their way of life.

UV light is a good example. Its importance in the lighting of many species is well known in reptile keeping, but some reptiles can also perceive UV light. Experiments with the common wall lizard (Podarcis muralis), for example, have shown that it enables them to distinguish visual signals that remain invisible to us.

Two lizards that look very similar to us may therefore display differences that we simply cannot see.

So, what might the world look like through the eyes of a reptile?

Turn off the light… the rules change

Look at a colourful object in a well-lit room, then observe it as the light becomes very dim. Gradually, the colours become more difficult to distinguish.

For some nocturnal geckos, however, they remain visible for much longer.

The helmeted gecko (Tarentola chazaliae), for example, is able to distinguish colours under extremely low light conditions, comparable to a night faintly illuminated by the moon. Under the same conditions, our eyes are no longer able to distinguish colours.

This does not mean that it can see in the dark. Its eyes are simply particularly well adapted to make the most of the little light available.

But not all geckos have the same activity patterns. Phelsuma, for example, are mainly active during the day. Their eyes are adapted to activity in bright daylight, and their colour vision is particularly well developed.

Two geckos can therefore have eyes adapted to very different light conditions: one to make use of the little light available at night, the other to thrive in broad daylight.

A striking example of the diversity that can be found even within a single group of reptiles.

The chameleon’s amazing gaze

If there is one reptile whose gaze is particularly fascinating, it is the chameleon.

Its highly mobile eyes can move in different directions, allowing it to observe a large part of its surroundings without constantly having to move its head.

It is often said that its two eyes work completely independently of each other. In reality, things are a little more complex.

When exploring its surroundings, a chameleon can look in two different directions and even track two separate targets at the same time. But as soon as its attention turns to prey, both eyes can coordinate and focus on the same target.

This ability becomes particularly useful when hunting. Before its tongue shoots towards an insect, the chameleon must first spot it, track its movements and accurately assess its position.

Its eyes therefore allow it to switch from a broad view of its surroundings to much more focused attention as soon as prey enters its field of vision.

Does a snake really “see” heat?

You have probably seen images showing a snake looking at a mouse depicted in shades of red, yellow and orange, as though viewed through a thermal camera.

The idea is based on a very real ability, but that is not exactly how it works.

Some snake species have organs capable of detecting infrared radiation emitted by their surroundings. This is particularly the case with pit vipers, pythons and some boas.

The royal python (Python regius) provides an easily observable example: the small pits along its lips are heat-sensitive sensory organs capable of detecting very slight differences in temperature.

This information complements that provided by its other senses and can, among other things, help it locate an animal that is warmer than its surroundings, even in low-light conditions.

But contrary to what the expression “seeing heat” might suggest, it is not the snake’s eyes that detect infrared radiation.

Most importantly, there is no evidence that a snake perceives an image comparable to that produced by a thermal camera. We know that it receives this information and that its brain processes it, but we do not know what this perception actually looks like to the snake.

Now look at your terrarium

After all this, take another look at a terrarium.

The colours you see may not be exactly the same as those perceived by its inhabitant. An area that appears almost completely dark to you may still provide visual information to certain species. And some reptiles can even perceive information, such as UV light or infrared radiation, to which we have no direct access.

We can study their eyes, sensory organs and behaviour to gain an increasingly better understanding of their abilities. But there will always be one limitation:

Knowing what an animal is capable of detecting does not mean that we know exactly what it sees.

This is why images that claim to show “a reptile’s vision” are, above all, representations. They can help us understand certain differences, but they cannot truly show us the world through a reptile’s eyes.

Ultimately, we can look at the same terrarium, under the same light and at the same moment as its inhabitant… without necessarily seeing the same world.