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Organisms on earth have a wide variety of ways to detect the presence of other objects. Echolocation, electrolocation, vision, etc. One kind they're missing is detection based around bouncing microwaves off things, i.e. radar.

On my planet I have a taxon of flying creatures that live their lives completely airborne. They mostly live at high altitudes except to feed on fish and other marine life that lives close to the surface. I'd like for them to be able to locate prey from high altitudes using microwaves or radio waves; it seems like a fairly logical adaptation and it's also just pretty cool. Echolocation is out due to its range being too short; my atmosphere is thicker than earth's but not that much thicker. (Echolocation in bats seems to be capped in the tens of meters; my creatures prefer to fly thousands of meters above the water.) In addition to locating prey they could also use their radar for communicating over long distances. (These creatures are fairly smart; not anywhere near human intelligence or probably even toothed whales, but around as smart as an elephant or racoon. They have some need to communicate, if only to find each other to mate, since they're often very far apart and unlike e.g. albatrosses they don't return to a specific area of land to mate.)

I'm wondering how feasible this is. Quite a lot of things on earth are bioluminescent but none, as far as I know, produce wavelengths beyond the infrared spectrum. My flyers don't necessarily have to do this chemically; producing electricity and using some kind of internal antenna to produce their radar would be fine too.

I realize radar does not penetrate water very well, but I think this isn't too big of a problem since they are only looking for things on or just below the surface.

In short: What sort of mechanism could my flyers use to generate their radar? How could they receive it? (antennas, special eyes?) What other sorts of problems might they encounter or what other uses could it have?

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  • $\begingroup$ A thicker atmosphere would help echolocation, not hinder it... and any range over a few centimeters would not be 'too short'. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 6:41
  • $\begingroup$ It would help, but like I said it's not thicker-enough to help that much. And if they're hundreds or thousands of meters in the air I think echolocation would be limited to when they're already right over the surface of the water—marginally useful but not quite what I had in mind. And definitely not enough for communication between individuals. $\endgroup$
    – Peter C
    Dec 3, 2020 at 6:57
  • $\begingroup$ You would mean that the range is too long for sonar to be effective, then. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 7:55
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    $\begingroup$ The surface of the water would function effectively as a mirror. The fish one meter behind it won't be distinguishable from the massive return of the water surface. There must be a reason why anti-submarine warfare doesn't even attempt to use radar, even if big metallic sumarines are very much better radar reflectors than tiny fish. $\endgroup$
    – AlexP
    Dec 3, 2020 at 8:57
  • $\begingroup$ @AlexP Water absorbs RF energy at the frequencies commonly used for radar. It tales ELF signals to penetrate water effectively, and the wavelengths are too long to use as radars against submarines. Given their ferrous construction, magnetic anomaly detectors are used instead. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 9:10

2 Answers 2

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In this answer, I show how a hive mind might evolve using metal-cored and shielded neurons. In this answer, I elaborate to show how biological radios might evolve, using partially shielded and unshielded metal-cored neurons.

So, if we have an organism with the ability to generate and receive RF energy - and, with direct mechanical rather than chemical-diffusion-based neural junctions - it is not a particularly large stretch of the imagination for such beings to evolve biological radar in much the same way that some species on Earth have evolved to use sound in a similar manner.

So... what would it need? It can already generate and receive RF energy, so to make a radar, it would need three things: directional transmission, a target that will reflect the emitted energy, and the ability to detect the reflected energy and calculate distance based on the duration between emission and reception.

To have directional transmission would require an organ similar to a bottlenose dolphin's melon, only for radio-frequency energy. This might be a metal-lined cavity similar to a microwave oven's emitter... though probably evolved to emit over a narrower angle. The organism would emit RF energy from this organ - or several of them, each tuned to a different frequency - and receive the reflected energy either with an omnidirectional receiver or a directional receiver, which might be the same organ, or it might be a different organ.

Once the RF pulse is emitted, reflected and received, with a faster brain that metal-cored neurons and mechanical neural junctions would allow, it would be little different to a dolphin's ability to interpret its sonar return for this being to interpret its radar return.

Being an evolved ability, this biological radar might ultimately be capable of feats that would make even the most capable man-made radar seem quite primitive.

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  • $\begingroup$ It would also need the ability to generate impulses. That is not trivial. $\endgroup$
    – AlexP
    Dec 3, 2020 at 8:55
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    $\begingroup$ @AlexP since each RF wave would be generated by one neural impulse, it is a given that these organisms would have that ability. This is in contrast to a man-made radar transmitter where the signal generator and the circuitry to switch the signal generator on and off are seperate. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 9:01
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    $\begingroup$ Neural impulses and radar impulses are very different things, which happen to be named with the same word. Generating usable radar impulses is definitely non-trivial. (Cowers under the blanket when remembering klystrons, magnetrons, wave guides and their cohort of horrendous acolytes.) (Yes, modern radar installations use all-solid-state phased arrays, but those are way beyond anything biology can make.) $\endgroup$
    – AlexP
    Dec 3, 2020 at 9:19
  • $\begingroup$ @AlexP True... but when it takes one neural impulse to generate one RF wave, the task of generating the RF impulse can be handled at least partially in the being's brain. If it is evolutionarily advantageous, there might even be a physical shutter. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 9:22
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    $\begingroup$ Generating the impulse is not the same thing as commanding the generation of the impulse. There must be machinery to generate (very) high-power high-frequency radio waves, machinery to direct them into one narrow beam, machinery to turn the beam on and off in a very very short time. Radar impulses and biology live on vastly different time scales, and on vastly different power scales. Remember that the point is to measure the time between emission and reception of the echo; this is measured in microseconds, and must be measured with a precision of tens of nanoseconds at least. $\endgroup$
    – AlexP
    Dec 3, 2020 at 9:28
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The biggest problem they would need to solve is how to not self blind themselves.

Let's say they fly 3 km above sea level, this gives a travel time to the surface of the water of 10 microseconds, which means that they should be able to emit their pulse while shutting off their listening mode and then revert it on in that amount of time.

Though that's doable with electronics it might be a tough cookie for a biological entity, where usually commuting times are in the order of milliseconds. Not mentioning that, even if they could manage to switch in 10 microseconds, they would still be blind to anything closer than 3 km, which often ends up being more dangerous the closer it is.

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  • $\begingroup$ You're assuming earth-animal-like neural transmission times and reaction speeds. This will probably not be the case with a species evolved to emit and receive RF energy. $\endgroup$
    – Monty Wild ♦
    Dec 3, 2020 at 7:47
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    $\begingroup$ When you throw a ball as hard as you can, the time between starting the throw and releasing the ball is so short that your body wouldnt be able to "react" to the start of the movement. But your brain basically engages a pattern, the signals to release the ball are already underway by the time your arm starts to move. It has to be evolved specifically, which explains why other creatures that throw stuff have such a lack of coordination when doing so. $\endgroup$
    – Demigan
    Dec 3, 2020 at 8:23

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