There is a predator that lives in the forest. It is roughly the size of a large bear, and moves quite slowly - a person could outrun it at a light jog. Nor is it agile - although its arms and jaws could easily crush a human once it has a firm hold of them, a person would have little difficulty slipping out of its clumsy grasp.

The reason this predator is dangerous is because its prey does not perceive it as a threat until it is too late. Somehow, it causes nearby animals to completely lose their sense of fear, which allows it to slowly nuzzle up against them in a big, furry hug before crushing their bones.

Is such a creature plausible?

I am assuming that the only way of achieving this would be for the creature to produce some kind of chemical or airborne drug. Is there any real-life chemical that could produce such a response quickly enough for this predator to catch prey?

If possible, the chemical should have as few side effects besides the removal of fear as possible; its victims should behave more or less normally, aside from the fact that they aren't concerned by this giant furry beast wrapping its arms around them.


The question is more about the gas than the creature; whether or not such an "anti-fear" chemical exists or can exist.

The chemical does not need to be strong enough to make the victim ignore pain; once the predator has a firm grasp it can continue squeezing or biting until the prey dies. It only needs to not be resisted while it's getting the grasp in the first place.

The effect should work on humans, but should not be exclusive to humans.

The creature does not need to be actively roaming; it can sit in a thick cloud of its own gases and wait for prey to stumble into it. But it's too slow to be a proper ambush predator; even if it snuck up from behind, without the gas the prey would quickly jump away in alarm the moment it felt the creature's arm starting to wrap around it.

  • $\begingroup$ Plants do similar things to lure insects. Plants usually do not move. Some predators attack by ambush - the animal doesn't fear because it doesn't know the predator is there, ready to attack. Your approach seems just so much less convenient. $\endgroup$ – Raditz_35 Jul 18 '17 at 12:22
  • $\begingroup$ Best I can find is a substance called Propanol, but that's not airborne and I doubt it can be made gaseous to retain the same function. ncbi.nlm.nih.gov/pubmed/20102667 $\endgroup$ – Hyfnae Jul 18 '17 at 12:30
  • $\begingroup$ @Raditz_35 I dunno, letting your prey come to you seems like a good way to predate. Save energy others would use hunting. If the creature has a slow metabolism on top of that, it could live for a stupidly long time on little food, and last an even more stupidly long time with an abundance of food. $\endgroup$ – DisturbedNeo Jul 18 '17 at 12:32
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    $\begingroup$ Right, but predators that ambush their prey generally do so by hiding and then striking very quickly when the prey comes close. This is something different... as for being less convenient, it would probably have evolved from a more conventional predator, developed the chemical to make hunting easier, and then became slower once it no longer needed speed to catch prey. $\endgroup$ – IndigoFenix Jul 18 '17 at 12:41
  • $\begingroup$ I think the tags are wrong. You are asking if it is plausible, and that is reality-check; you shouldn't use it together with hard-science; And even if you don't agree to swapping the tags above, you should add creature-design. $\endgroup$ – Mindwin Jul 18 '17 at 13:55

The thing about fear or alarm is that it arises in response to a stimulus. When conditions are right there should be fear. To get your predator to work you would need 1: an organism whose reactions were largely pheromonally mediated. So, an ant. 2: The predator would need to make some pheromone that was a receptor antagonist against the alarm pheromone. The thing is, usually alarm pheromones are something you give off as you are attacked, and then I come to help (or I run. Probably run. To get help, of course.) The individual being attacked does not need an alarm pheromone to realize what is up.

I think a better way for the predator to work is to use a different pheromone from a different signal system, in amounts and potency so great that it overwhelms other competing pheromonal signals (like fear or alarm). I know there are animals that pheromonally imitate ant / bee larvae and so are fed and cared for, sort of like cuckoo birds. I thought there was a predator that smelled like a larva but then ate the ants who tried to care for it. Plausible, even if I did not turn it up. Your huggy bear could be a huggy killer fake baby with fake baby smell. Everyone around is busy thinking about babies and is not alarmed that their friends are getting hugged and eaten.

But on looking for that I found this wasp: not only are its larvae fake ant babies, but the adult emits rage pheromone: the ants go insane and attack each other, leaving the wasp to do as it will. So cool I have to link.

from http://www.sciencemag.org/news/2002/05/treacherous-wasps-turn-ant-against-ant

In European grasslands, Maculinea caterpillars fall off their host plants partway through development and attract red ants, which carry them to their nests. There the caterpillars, protected by chemicals that mimic those of ant larvae, are fed and tended by adult ants. Meanwhile, the wasp Ichneumon eumerus comes calling. It lays eggs in the caterpillars; the wasp larvae feed off the caterpillars and hatch during their pupation. They then leave the nest, soon ready to mate and find more nest-bound caterpillars. But how the wasps get in and out of the nest without being killed by the ants has been a mystery.

In the 30 May issue of Nature, ecologists Jeremy Thomas and Graham Elmes of the Centre for Ecology and Hydrology in Dorset, United Kingdom, and colleagues reveal the wasps' trick. The researchers isolated and synthesized six chemicals that the wasps secrete--four of them new to science. Experiments in the lab showed that these chemicals whip the ants into a frenzy, wildly biting and stinging one another--providing a distraction that allows adult wasps to enter nests and hatching wasps to escape.

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    $\begingroup$ For example releasing huge amounts of en.wikipedia.org/wiki/Oxytocin? $\endgroup$ – Alberto Yagos Jul 18 '17 at 15:14
  • $\begingroup$ I think oxytocin is strictly vertebrates. We have other inputs which clue us in as to when it is time to run. A bunch of airborne oxytocin would definitely confuse the matter. Its role as an amnestic would be an interesting use by a predator... $\endgroup$ – Willk Jul 18 '17 at 15:37

Oxytocin analogues

Oxytocin is a complicated hormone, and we still don't fully understand how it works. It's commonly called the "love hormone" because of its role in bonding, but it has many other functions as well; its scientific name, for instance, comes from its role in childbirth, and it's been found to affect everything from dishonesty to drug addiction.

But it does have one function which is fairly well understood. After using a nasal spray including oxytocin, subjects showed significantly less amygdala activity when shown frightening images. The amygdala tend to be involved in fear responses; if they're damaged, people tend to show no fear whatsoever. So inhaling airborne oxytocin can certainly reduce fear responses.

Almost all vertebrates have oxytocin, or a hormone very similar to it. So if your predator hunts vertebrates, releasing large amounts of oxytocin into the air (or water, depending on habitat) would help prevent immediate panic.

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It's not on the same scale, but here is an article from Nature that talks about a spider attracting moths by mimicking their sex pheromones:


Some quotes:

A spider lures two moth species to their doom by mimicking both their sex pheromones, researchers have discovered. The spider changes the blend through the night, to attract species that are active at different times.


Next the spider releases chemicals that imitate the sex pheromones of female moths. Male moths come in search of female company; the spider swings its silky lasso and hauls in a meal.

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