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Could an animal use radiation as a defense mechanism?

Some animals use electricity, claws, venom, or poison, but could an animal evolve to use radiation as there main defense/means of hunting? How realistic is this? How would they do it?

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  • $\begingroup$ Keep in mind that the glowing green and purple stuff called radiation you see in video games is as divorced from reality as any magic. $\endgroup$
    – sphennings
    Sep 24 at 18:16
  • $\begingroup$ Short answer is no. Radiation takes too long to kill to be a useful defense mechanism against anything except microbes. Even in the worst radiological accidents we've ever had, the victims didn't die immediately. $\endgroup$
    – stix
    Sep 24 at 18:28
  • $\begingroup$ If the creature can maybe develop some kind of linear accelerator to create a beam of highly energetic partials to create ionizing radiation, then maybe. Then the creature would not need to carry around highly toxic metallic isotopes with them. However, that wont exist in nature. $\endgroup$
    – Sonvar
    Sep 24 at 21:06
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Some Already Do

In the Chernobyl exclusion zone, flora and fauna are doing better, in many ways, than they did pre-irradiation, by means of the radiation driving off their major competitor - namely, us. They have to suffer the effects of the radiation, but it's a lot less trouble than human civilization/human predation.

More Realistically

Radiation is a terrible means of both defense and hunting, because at levels that don't just destroy cells wholesale, it's neither immediately painful nor immediately lethal.

It doesn't do a predator any good to expose its prey to a subcritical source of radiation and then find them two days later when they've bled to death. Similarly, it doesn't do a prey animal any good to expose a predator to a radiation source and then have the predator die a couple days later.

If a creature had radioactive materials in their flesh to act as a sort of poison to dissuade predators, the heavy metal poisoning from those materials would occur before radiation poisoning.

So beyond adapting to live in radioactive areas (or simply tolerating it), no, there's no realistic fashion where a creature would use radiation for hunting or defense.

Edit: I should follow that up with "at levels that do destroy cells wholesale, you have two problems." The first is trying to find a means of defending against the cell-destroying radiation intensities. I can't imagine earth-based life evolving to the point where its cells are so radically different that they aren't susceptible. The second is that radiation doses sufficient to kill prey quickly will have strongly negative effects on their nutritional value. The denaturing of proteins and destruction of cell walls quickly breaks down key nutrients, which would make it an undesirable outcome.

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  • $\begingroup$ "the heavy metal poisoning from those materials would occur before radiation poisoning" - this depends on level of their radioactivity. But in general, I agree with your reasoning. $\endgroup$
    – Alexander
    Sep 24 at 17:37
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    $\begingroup$ Highly radioactive isotopes have commensurately short halflives, @Alexander, so anything that violently radioactive would have to be regularly replenished and spread through the critter in question. Even if we assume they can withstand that, it's energetically expensive. $\endgroup$
    – jdunlop
    Sep 24 at 18:08
  • $\begingroup$ Assuming an animal has a lifespan of one to two years, consuming isotopes with 6 month half life would likely present more danger from radiation than from heavy metal poisoning. $\endgroup$
    – Alexander
    Sep 24 at 18:12
  • $\begingroup$ There are a few isotopes that are highly radioactive and with relatively long half lives, it all depends on how energetic the decay is and what method it decayed, (such as alpha or beta.) isotopes of plutonium is one. However, like you mentioned, its toxicity is far more lethal than the radioactivity. $\endgroup$
    – Sonvar
    Sep 24 at 21:03
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    $\begingroup$ "it doesn't do a prey animal any good to expose a predator to a radiation source and then have the predator die a couple days later" -- Actually, having predators die after eating you is quite useful when the predator knows the danger. $\endgroup$ Sep 25 at 2:18
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Yes, for a given value of radiation

When you say radiation, you probably mean ionizing radiation. As jdunlop explained, using this is suicide.

But guess what, visible light is also electromagnetic radiation! Some jellyfish that live in the abyssal zone are bioluminescent, but they only light up when they are attacked. One idea is that if they are predated, the display they put on would attract even bigger predators to ruin the day of their attackers:

While it has been observed only anecdotally, some siphonophores and ctenophores (see phylogenetic tree) are presumed to use bioluminescent body parts as “sacrificial tags.” If an organism loses part of its body to a predator, the lost tissues can continue to glow, even in the predator’s stomach. Since many deep- sea creatures are transparent, this draws attention to the predator and makes consuming bioluminescent prey risky.

So even if the jellyfish dies, its attacker will die as well, thus making an appetite for jellyfish a deletarious trait.

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    $\begingroup$ A good example of this would be some guy in the quiet place universe screaming at the top of his lungs whenever someone tried attacking him with a machete or other bladed weapon. $\endgroup$ Sep 24 at 17:44
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As others have said, ionizing radiation won't be any good at short-term killing, but it may kill in a couple days. Although far-fetched, one could imagine prey that held a shielded radioactive core within them, where the shield requires active maintenance. Therefore, a dead animal would soon enough start emitting radiation, which would kill predators in a few days. Now, this won't do any good for the dead prey, but as a species predators would eventually learn and stop hunting them. Couple this with a characteristic mark such as bright colors or a certain pattern on their skin and predators will soon enough learn to recognize this pattern on prey.

In fact, this kind of happens already in nature, although not with ionizing radiation, but with poison. Poisonous animals usually have bright flashy contrasting colors, a phenomenon called aposematism. Many poisonous animals are not toxic enough to stop the predator before it is done killing the prey, but will serve as a deterrent for future predators. Since radioation can be considered as a type of poison (in fact the effects of radiation are called radiation poisoning), it could be used in the same way.

So yes, radiation could be used as a defense mechanism, but not as you might expect.

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