So there is a race that is supposed to be able to switch from the visible spectrum to infrared, in about 10 seconds.

I was thinking it might be a double retina, and the eye has some muscles to move them about, or the eye has two holes and it can turn up enough so light now engages the other retina, or just a more complex lens construct. Or it could be some physics or chemistry based mechanism in the retina cells, that turns them sensitive to the different wavelength. Or it can all be in the brain.

It's fairly standard fantasy, and some slightly magical explanations could also work.

Which one of these or any new ones you can think of would work best as something that could have developed, not necessarily entirely naturally, but it can be inherited to half breeds to a lesser degree.

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    $\begingroup$ Infrared vision is tricky for warm blooded creatures since they innately shine in infrared from within. $\endgroup$
    – alamar
    Mar 25, 2021 at 11:56
  • $\begingroup$ @alamar it may not be as hard as you might think; it [could be done artificially right now], for example. An organic system obviously faces more engineering difficulties, but they aren't necessarily insurmountable. $\endgroup$ Mar 25, 2021 at 13:00
  • $\begingroup$ Is it important that it switches (one or the other) or can the 2 be used simultaneously $\endgroup$
    – Stilez
    Mar 28, 2021 at 10:18
  • $\begingroup$ @Stillez It is important, since I try to build the background for a world that is already has some fixed details. $\endgroup$
    – Martin S.
    Mar 29, 2021 at 11:29

1 Answer 1


Before I begin, it's important to tell you that infrared light is something that essentially all warm blooded creatures release (yes we all constantly glow, just not in a wavelength that we can notice), so depending on whether your creature is exothermic or endothermic it'll make it easier or harder to make use of this ability. With that said: let's look at our possibilities for perceiving infrared light:

1-Like frogs

As it turns out, both fish, particularly salmon, and amphibians have an enzyme that allows them to see infrared. What this chemical does is that it essentially changes vitamin A, related to better vision in low light, from A1 to A2, which means what the enzyme does is, and I quote:

switches the visual systems of some fish and amphibians and supercharges their ability to see infrared light.

This however seems to be linked to the eye being undewater where it's harder to see, as when analyzing bullfrogs which could see both above and below the water, they discovered that only the part of the eye underwater had the enzyme acting. Nevertheless, we see it exists, and as their tests showed, if a fish that normally had this enzyme had it disabled while in a dark aquarium they'd not react to infrared light while a fish that had the enzymes working would swim towards said light, so we can see that it could theoretically be a "toggable" ability if your species can control when these enzymes are produced and when they stop to work.

2-why use your eyes?

You see, your eyes are already working just fine as they are, they let you see, just not in infrared. Instead of going in like frogs and fish and go changing your eyes, why not use something else to see infrared? Like what? Let's look at pit vipers and bats shall we?

enter image description here

If you pay attention to the face of the snake you'll notice how it seems to have 2 nostrils, a bigger one and a smaller one right in front. Those bigger ones aren't nostrils, they're pit organs, these sensory structures possess a membrane that detects infrared light, and is mostly used by the snake to hunt warm blooded animals at night. While this doesn't work by "seeing" infrared per see, as the organ works more like extreme termoreceptors than it works as eyes, but the fact it can work even when the snake is blindfolded is clearly an advantage.

enter image description here

Another little guy that makes use of a similar strategy is, surprisingly, a mammal. The vampire bat, due to its lifestyle as a sneaky parasitic mammal, has evolved a series of adaptations that make it unique in several ways, one of which involves its face having evolved so that its nose is just far away enough from the body for it to remain constantly at ambient temperature. Why? Because much like pit vipers, vampire bats also have their own variation of "pit organs" located around their nose, which they use to find warm blood vessels closer to the surface of the skin. While this ability of theirs isn't quite as impressive in terms of detecting at longer distances (they can detect blood vessels from up to 20 cm away, while pit vipers can "see" warm prey up to a meter away), they still show that, with the right configuration and by not relying on your eyes for it, mammals too can detect infrared light if they have their faces adjusted in the right way (in this case, as a lovelier, fuzzier version of Nosferatu) .

  • $\begingroup$ Hah, I did not know that about vampire bats. Fascinating stuff. $\endgroup$ Mar 25, 2021 at 13:01

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