Just a silly idea for some sort of potentially major event, but what would happen if say the mind of cat entered the body of a mouse and vice versa, for every animal on Earth? Let's also assume that for hierarchies of predators and prey, the animal's mind is "shifted" down a level e.g. the hierarchy of bodies Large Bird -> Small Bird -> Insect would have the hierarchy of minds Insect -> Large Bird -> Small Bird.

  • $\begingroup$ Welcome to the site! While the question on its face is probably answerable, we do tend to thrive on detail around here; the more detailed the question you ask, the more detailed (and sometimes surprising) answers you tend to get. For instance, what happens in this scenario to animals like small birds that are both predators (to insects) and prey (to larger birds)? $\endgroup$
    – Cadence
    Jun 10, 2018 at 9:20
  • $\begingroup$ @Cadence Thanks for the tip. Would you like me to edit the question? $\endgroup$
    – user51778
    Jun 10, 2018 at 9:23
  • $\begingroup$ By all means. You can always edit your own questions with clarifications or if new details occur to you. You can also clarify in comments if it's specific to that one person's approach to the problem, but that's rare; you should usually edit the question so everyone sees it. $\endgroup$
    – Cadence
    Jun 10, 2018 at 9:35
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    $\begingroup$ For this question let's assume that they do indeed have minds. $\endgroup$
    – user51778
    Jun 10, 2018 at 10:28
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    $\begingroup$ I am having trouble understanding what you are proposing given a) the disparate numbers at different levels of food chains and b) which way animals in the middle of the food chain move. For example, baleen whales live by consuming vast numbers of krill etc, and are preyed on sometimes by killer whales and humans from certain nations. Given that there are orders of magnitude more krill than baleen whales, does one krill swap with the baleen whale? What happens to the other krill? If the baleen whale swaps with a killer whale, do any of the krill swap with anything? $\endgroup$ Jun 10, 2018 at 13:54

5 Answers 5


A wolf has fallen into a beartrap. He's trying his damnedest to set himself free, he's agonizing in the snare of the iron biting into his flesh.

A poacher arrivers. He's satisfied, a trophy to adorn his house, a pelt to sell for hefty money. He's moving with prudence toward his prey, ready to inflict the coupe de grace...


The poacher's vision turns to a world of different colors, smells, sounds, and pain, so much pain, his leg is on fire, oh God my leg! for a moment there is nothing but pain, he checks is leg and terror, sheer terror invades him as he sees an alien shape where a second ago was his body! He looks around...and sees himself standing there, in a state of shock. Do I really look that funny? he wants to elaborate...only to discover that he can't translate this concept into words. In fact, his mind is devoid of his own vocabulary! His mind is filled with...something else. He can't understand his own reflections, his own inputs. For now, there's only the pain. He tries to call for help, but only a canine yelp comes from his throat...

The wolf is frozen. Raw fear. Fight or flight? What happened to me? I am tall! I am free! I am...standing? His new body is hardwired to stand, but his mind is caught by a vertigo, he tries to stand on all four. His vision is filled with colors he didn't know now that his eyes can catch the red part of the spectrum. He sees himself. He growls. Is it a rival? A packmate? He smells vaguely familiar...but now his keen sense of smell is almost gone, and he's panicking, he can't focus. And the only smell he feels stronger it's the hated man's! It's all around him, as if he was coated in it! Reflexively, he uses a paw to clean his snout, founds nothings, no long snout. MY PAW! THIS IS NOT MY PAW! He tries to move, collapses, his body is not made for his natural posture. Pack! Pack, where are you?!? But he can't find his scent track. He is lost...

And this is just one case: In the seas, the crew of a fishing boat suddenly collapses on the deck in a fit of panic. Some of them will die of raw fear, some will plunge into the familiar sea to go home, just to discover that they cannot breath underwater and will drown, all the while their preys in the nets will meet their fate knowing, for just once, what's the feeling of asphixiating outside the sea...

All around the world, cats go into fits of panic, as they start to act like mice -and being mice able to fight back if threatened, they attack the owners who are only trying to calm them. Other felines just try to scurry away like lizards. A kid who was about to stomp an ant becomes a mindless mannequin, cut away from his nest...

Final effect: civilization ceases to exist, food chain collapses at all level, except for the microbiotic level. Plants that need impollination will soon follow since there will be no more impollinators able to do their job. Soon Earth is on its way to become all-green again, in a new ecosystem where plants have no enemy and microfauna can thrive on the remains of the larger biomass. How this will affect its relationship with the greenery remains unknwon.

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    $\begingroup$ This is probably the best written on World Building, maybe even SE! Sounds more like a short story rather than a regualr answer. +1 $\endgroup$ Jun 10, 2018 at 14:00
  • $\begingroup$ A few typos and some narrator/character POV jumping mid-sentence, but apart from that: very well written. $\endgroup$
    – wizzwizz4
    Jun 10, 2018 at 16:03
  • $\begingroup$ Sorry, English is not my mother language, will do better next time^^ $\endgroup$ Jun 10, 2018 at 16:10

There are several "levels" of predators, from predatory insects that can only feed on specific prey, to hypercarnivores like cats, which can survive on just about any kind of meat, to hypocarnivores like bears and humans that eat meat, but can do without.

Marine life will be hit the hardest, as it's got a very long food chain. Only specialized marine life can consume plankton. Since all the minds got swapped, though, lifeforms violating their role won't become easy prey.

All in all, most primitive carnivores will die out, as they have little diet variety. Bird bodies will mostly die out, as flying requires specialized instincts. Some bird-to-bird swaps may survive. Probably 99% of non-reef and 90% of reef marine life will die out.

Human bodies will die out, as they can't be sustained without intelligence. Human minds in our primary animal food, large herbivores, should have a good survival rate. But boy it's going to be boring with no internet and SX!


They would starve, because they lack the necessary knowledge and instincts to feed themselves.

First, they might not even know how to control their new bodies.

If they do learn how to even walk before starving, the mouse in the cat's body would try to eat fruits and grain. It wouldn't be aware that its digestive system can not metabolize them. The cat in the mouse's body would try to hunt with its weak claws and small teeth, which would be unsuccessful too.

  • $\begingroup$ Is it possible that some species would survive? Predators and prey that have somewhat similar diets or mindsets? $\endgroup$
    – user51778
    Jun 10, 2018 at 10:37

Its going to get bloody, and quickly.

Lets look at a Fox and a Rabbit for now, because the cycle you described was one of predator eating smaller predator eating smaller predator while you are really asking for a predator/prey swap. Despite the anatomy, many nerves and muscles will have the same wiring, and brains adapt quickly to change so they'll be able to move effectively before starvation/dehydration.

The Fox thinks its prey now. It also thinks leaves and such are now its food. That will eventually kill it. But that eventuality is going to have to wait.

The Fox is standing in a field somewhere as it happens. It is suddenly surrounded by maybe 200 rabbid Rabbits per one Fox, not to mention all the other critters that are suddenly lusting for Fox. Rabbits are now sneaking up on the Fox, and the first Rabbit takes a sprint at it.

The Fox will take off, and any direction it goes in more and more Rabbits give chase until the Fox stumbles or is foxed (heh) in. Now the Rabbits will try to give the Fox a fluffy Grave, but the Fox will now try his last stand as he thinks he's about to be devoured... Only to find that its rather effective at defending itself. The Rabbits can scratch and bite but have trouble killing. Many Rabbits will succumb to their wounds or stop the attack upon finding too much resistance.

Unfortunately for the Fox, by the time he's fought off his first round of attackers the second round is looking to see if all that noise might be a wounded prey they can easily devour. It'll eventually die of exhaustion or the slow flaying of its skin caused by all those Rabbits and critters.

End result: most of them die from wounds and exhaustion, the remainder dies from starvation.


Any species that gets our minds and can eat plants will survive

Humans are very adaptive and have a rather large variety of foods we eat. As such any animal that gets ours minds and has a diet not critically dependent on a different animal will likely survive.

Apocalypse Happens for Humanity

Humans rely heavily on their minds to keep things going, so for all humans to have the minds of the most basic creatures would result in everything humans maintain falling apart.

Chickens Survive

Humans eat a lot of chicken and we are their primary predator, so it makes sense that they would get a large share of the human minds. Combined with the information in the linked question, I am going to assume intelligent chickens will take over the world.