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By active night-vision I mean that it emits light in a wavelength other animals can't see, but it can perceive that wavelength, so it can see even in zero-light conditions.

Being able to emit light already exists, some insects, and some deep-water fish can do it. Although it's still strange what intermediate steps can be useful, in order to be selected for.

The biggest hurdle, I guess, would be that if the prey species evolved the ability to see in those wavelengths, the predator would be disadvantaged, as it would be shining brightly in the night.

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  • $\begingroup$ unlikely unless you are talking about blind cave dwelling species. $\endgroup$
    – John
    Dec 30, 2017 at 17:33
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    $\begingroup$ The intermediary steps might not have anything to do with emitting light. IOW, they were either harmless mutations, or valuable on their own. $\endgroup$
    – RonJohn
    Dec 30, 2017 at 20:59
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    $\begingroup$ A fun idea - your I.R. Panther could have some sort of symbiotic relationship with, say, some insect which emits IR light. So, for some reason a small cloud of these insects fly around with the IRP. There/s some kind of signaling process from the IRP to his IR-Emitting-Crew. (Say, when during hunting the IRP tenses, blinks, or whatever.) {Maybe they even know to disperse themselves circularly, so that there is no real target for the prey.} At that moment the IREC give a flash of IR light. The IRP then easily kills-N-eats the prey. The IREC insects benefit somehow - rinse and repeat! $\endgroup$
    – Fattie
    Jan 1, 2018 at 14:56

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Ah - it turns out this already exists!

Who knew?

I was going to point out in a comment: "on our planet, many creatures do emit light. So the only question is, would it be feasible to emit infrared light via that mechanism?"

I then thought .. "Hell, I maybe I should search 'infra..' on the wiki bioluminescence page."

https://en.wikipedia.org/wiki/Bioluminescence

Bingo!

enter image description here

So there's no barrier at all to a creature emitting IR - it exists already.

LDutch mentioned "to any prey [sensible] to IR light this will look like a ringing bell"... However, echo-location type techniques are common in animals (and electro-location also is known to exist and is amazing). So I'd say it would be perfectly plausible that the hunting animal would simply flash the IR source very briefly and in a very controlled, precise way (as with -location techniques) to get a reading - it wouldn't be on all the time as a giveaway.

It's actually surprising that we don't already have a predator (perhaps an insect) with active-IR night vision - maybe we do but haven't found it yet.

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Every body at a certain temperature already emits light according to the black body theory. For living range temperature this light is in the infrared spectrum.

Your predator can evolve an area with higher temperature on his body, somewhere on the forehead, that shines infrared light. The emitted light is then reflected by surrounding, allowing the predator to see even when no outer light source is present.

Conceptually this is not so different from safety camera which have a circle of IR LED around the iris. (see pic)

security camera

Shortcoming of this configuration:

  • to any prey sensible to IR light this will look like a ringing bell
  • additional metabolic needs to keep the area warmer
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What about alternatives?

Cat eyes work differently: there is a higher sensitivity in the cornea, the cornea itself is large, the shape of the pupils and that famous reflective layer (the actual "cat eye" reflection) that boosts sensitivity. The price is worse colour perception. Details here.

Sending out some ways and fishing for reflection is the way radar/sonar works, just with different frequencies. Sonar in biology spells "bats".

Some species of deep sea fish function the way you describe (but I doubt the way you want it). They can emit light, have sensitive eyes, and mostly use the light as a lure for their prey.

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Bear in mind the inverse square law; double the distance the intensity falls to a quarter. Also, there's presumably some ambient light, so your animal's emissions would have to be all the stronger to not get lost in this.

Angler fish operate in almost pitch darkness and at short range (the lantern is literally right in front of its face), negating both these drawbacks.

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