Could a creature carry its own ecosystem around with it? What traits would it need to make this viable?

These self-sufficient creatures are native to planet which is for the most part frozen and covered with snow with a thin atmosphere that allows a lot of radiation through. These conditions don't allow much plant life to thrive except on a few habitable zones. The planets habitable zones host many native species but are rather restrictive in terms of space. So these creatures which are resistant to the cold environment carry around their ecosystem within their bodies. Due to this they can avoid the intense competition entirely by venturing in the less hospitable environments.

So here are the traits this specific creature needs:

1 Cold resistance.

2 A means to cope with their poor atmosphere.

3 Adaptations to survive solar radiation.

4 An inner biome to produce food and recycle waste.

They are gentle giants (about the size of a polar bear) with a nomadic lifestyle, thus they rarely ever visit the competition filled habitable zones. They lack any sort of natural defense against predators except maybe for their blubber and rely entirely on their hostile environment to keep predators away. They are slow moving, have very long lifespans and can communicate over long distances. They are not very intelligent but occasionally move in herds.

Edit: It seems there has been a misunderstanding about the term "self-sufficient". By that I meant an autotroph. A creature carrying around a biome of algae could recycle its waste using solar energy which is abundant on said planet. It is by no means a perpetual motion machine, which is why it uses solar energy and occasionally refills its recourses by visiting the habitable zone. Thank you for understanding.

Edit: A means of making up for the square-cub law would be most appreciated as you have done well answering the other aspects on this question.

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    $\begingroup$ Self-sufficient for how long? We have these creatures called humans who are perfectly able to carry enough environment with them in outer space to survive for quite some time. $\endgroup$
    – AlexP
    Commented Dec 31, 2019 at 19:58
  • $\begingroup$ I can't answer that, because I haven't received any details about how well the creature would function. Also how come every time I make a post about creature design, people throw the "humans can do it already" argument? This is creature design as I recall, humans have nothing to do with anything. $\endgroup$
    – user71341
    Commented Dec 31, 2019 at 20:59
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    $\begingroup$ Humans are creatures. If humans can do something, this means that the question already has an answer, in an example of a real living creature which can do it; and it shows that complicated evolutionary paths are not needed, humans being pretty close to the unspecialized archetypal general plancetal mammal as far as anatomical attributes are concerned. $\endgroup$
    – AlexP
    Commented Dec 31, 2019 at 21:04
  • $\begingroup$ That just makes the point of the question irrelevant. $\endgroup$
    – user71341
    Commented Dec 31, 2019 at 21:21
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    $\begingroup$ The solar radiation works in your favor here, that is energy that can be harvested. $\endgroup$
    – John
    Commented Jan 1, 2020 at 5:50

6 Answers 6


Our (distant) ancestors evolved to live in the ocean with particular salinity, nutrients, temperature, etc. To move into more hostile environments, we evolved ways to carry that "perfect" environment with us inside our bodies. For instance, no matter where you go, your body always has the same salinity level as the primordial ocean regardless of how much salt or water you consume (well, if taken to extremes, you die).

It's not difficult to imagine creatures that evolved inside a different "perfect" environment doing the same, nor evolving similarly to carry it into even harsher environments than we do. We have examples of your traits 1-3 here on Earth, so that seems settled.

Trait 4 is where it gets tricky. From your (edited) description, I think you're describing a photosynthetic symbiote. The problem is that photosynthesis doesn't produce much energy per area compared to how much energy an animal needs just to maintain homeostasis in a hostile environment, much less do anything interesting. For instance, XKCD estimated that a photosynthetic cow could only meet 4% of its energy needs. A big part of that is probably the square-cube law, though, so what if we inverted that to a flat-ish animal with a transparent bubble full of algae on its back? That seems plausible.

  • $\begingroup$ Could you edit your answer please? As soon as you started talking about trait 4 you seemed to have misunderstood the question entirely. The environment was set so that this specific adaptation would be worth it, the creature avoids its dangerous environment just like a seal would go on land to avoid predators. Lastly you realize that carrying your own biome means you get energy via photosynthesis right? Was that not obvious? I even specified that the planet gets a lot of solar radiation. Oh well... the first answers are never perfect. $\endgroup$
    – user71341
    Commented Dec 31, 2019 at 21:19
  • $\begingroup$ Wonderful! I have nothing else to say. $\endgroup$
    – user71341
    Commented Dec 31, 2019 at 23:19
  • $\begingroup$ 4% of their energy needs. So you're saying if you froze this critter solid reducing their energy use to 0% for 25x longer than they are active you could have a freezable space cow? Assuming the radiation energy of blue and red light is roughly equal to the space radiation energy. $\endgroup$
    – Tatarize
    Commented Jan 1, 2020 at 7:07
  • $\begingroup$ Don't reptiles use much less energy than mammals? Especially the ones that live in deserts. $\endgroup$
    – endolith
    Commented Jan 1, 2020 at 13:37
  • $\begingroup$ @Tatarize If it could survive the freeze/thaw cycles, that also seems plausible, but we don't have any examples on Earth of large animals that can do that, so there may be something I'm missing. $\endgroup$
    – StephenS
    Commented Jan 1, 2020 at 23:10

Could a creature carry its own ecosystem around with it?

Absolutely. As some of the other answers have pointed out, all life on earth currently does exactly this. Your idea takes this to an extreme, but the fundamental theory is well grounded.

As for how probable this is, I think that is irrelevant. How probable is it that Eukaryotes incorporated a separate, simple organism (now the mitochondrion) that uses oxygen (toxic!) to produce energy? Of course it's improbable, the very concept of life is improbable. But possible? Very.

What traits would it need to make this viable?

Radiation resistance, as you mention, is definitely important. The radiation resistance could neatly resolve another matter - collecting energy solely through light. Photosynthesis using Terran chloroplasts probably isn't going to cut it in terms of raw energy output. A chloroplast-equivalent that evolved on that planet could very well be able to take advantage of intense radiation levels. With this one adaptation, your creature can solve it's energy and radiation troubles.

Temperature resistance adaptations are more easily cited as there are plenty of examples of animals here on earth managing to get along just fine in frigid climates. To further incorporate the inner-biome idea however, consider an internal organism that metabolizes some simple compound very exothermic-ally. Granted this heat is just energy that could have been used elsewhere, but maintaining a stable temperature for the other symbiotes to thrive seems worthwile. For bonus points make the compound a waste product to help solve your recycling issues.

Maintaining a stable internal temperature and collecting enough radiation will prove to be a delicate balance. As surface area increases, so does radiation absorption and heat loss. Hair would interfere with radiation absorption, but provide valuable insulation.

Your creature would also need some way to collect micronutrients that aren't available as gasses in the atmosphere. Even though plants collect their energy from the sun, they must collect their nutrients from the soil. This might be one of the trickier parts to figure out, but definitely doesn't kill the idea. You may also want to consider how this creature reproduces and what the young look like. Small offspring will struggle to maintain thermal equilibrium and present enough surface area to collect radiation. Large offspring require a considerable energy investment from the parent, but would probably have a better change of not freezing.

All in all, awesome creature idea that definitely holds water (and other creatures).

  • $\begingroup$ Would using methane gas as a waste product be sufficient to keep the symbionts at an adequate temperature? $\endgroup$
    – user71341
    Commented Dec 31, 2019 at 21:57
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    $\begingroup$ Hair is an Earth thing for amniotes you could certainly replace the hair with radiation-autotrophic heat-insulating moss like stuff, the problem is the energy from the radiation falling on the surface of a bear sized thing would basically need to be so high as to warm the planet. If the creatures only needed to be active for like 6 months every 50 years or so, you'd get by. I mean long living, maybe they hibernate a couple decades enough to build up their energy reserves to travel to their breeding grounds. Otherwise there's just not enough energy on the table. $\endgroup$
    – Tatarize
    Commented Jan 1, 2020 at 7:04

It doesn’t sound very plausible to me. The problem is that the organism will need to get a supply of energy from somewhere to be able to move and have an active metabolism. Carrying a biome around with you to supply that need might sound like a good idea but it would not be efficient enough. For example an adult elephant consumes 200-600lb of food a day or at least a ton a week.

To grow that amount of food would require a huge area. Even with modern farming methods at say 1-8ton /acre/year would not be nearly enough and an animal with an foot print of an acre would weigh more than an elephant.

To make things even harder it’s a cold climate so sunlight is weak and not conducive to mass production of food.

The best that could be hoped for would be an organism that hibernated for most of its life and moved very little and very infrequently, but even then I doubt there would be enough energy available to sustain the organism with requirements for growth, some mobility, bodily repair and some basic metabolism.

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    $\begingroup$ Yup, this is the real problem. Coral and some jellyfish are a good model for carrying it's own food source, but if you're carrying your own food source you're operating at plant level energy, not animal level energy. $\endgroup$ Commented Jan 1, 2020 at 15:23

I think this question is rather terrestrian. In that it's asking for a lot of stuff for an alien creature that only really makes sense in context of human-like or earth life. And kind of views the world at the level of organism. First off, life forms are themselves carrying around their own biome. Like all of them, it's kind of what a multicellular lifeform is. It's a lot of different cells that work together in important and cooperative ways. I cannot digest most the things I eat but there's a bunch of stuff in my gut that can turn that into things. Also, my body heats itself up because that's the chemistry runs faster in the warmth, a lot of that chemistry is done by mitochondria which is a different critter than my cells are, or I am.

So note, everything you're asking for is perfectly reasonable and to some degree stuff that life does well. We live in an atmosphere that is one filled with oxygen, one of the most corrosive substances known as communities of cells, and in cooperation with bacteria etc. And things live in habitable zones. That's why those zones are habitable, things live in them. Extremophiles are often more the rule than the exception. Life is quirky like that.

The only thing you need is energy. You have a bear sized creature that is lives a nomadic lifestyle. It needs energy to perform this movement. And generally it will tend to need a reason to be nomadic. Animals don't waste energy going places if they make their own food. Trees are not known for being the quickest creatures on the planet, in part because they make their own energy. But, while some trees are bear sized, they are absolutely not nomadic. They move a bit towards the sunlight but it's certainly not very fast.

Bears can easily gobble up 20,000 calories a day, sometimes as much as 100,000 when the energy is plentiful and then hibernate when it gets cold. So what exactly on your planet provides this massive amount of energy, in some particular place, that these animals must go to in order to survive? And if there's a bunch of energy out in the snow, why aren't there other creatures that eat it?

You could certainly make them basically as large as bears and active as rocks sucking down the energy of the space radiation, because they live in a communal relationship with some crystal fungus but that's not really nomadic. Or you could make them kinda active like bears but then they need the alien equivalent of scarfing down a whole crap-ton of fish, or a consistent diet of some other energy source calories a day, which then wouldn't really require the nomatic part of it. They could very much graze some kind of radiation consuming moss like stuff for energy, or rather take it with them in some fashion.

But, there'd be some reason the radiation consuming moss would need to get around on a bear like creature. Plants, because they make their own food aren't the most cooperative of species. You might be able to get 3000 calories a day from intense space radiation, but that amount would certainly warm the place up pretty significantly, if it had to fall on the surface of a bear. Is there something else, like methane snow a bunch of oxygen around? If you have chemicals that can release a lot of energy together, you could certainly have some biome help with the conversion to usable energy.

--Edited to add:

1 Cold resistance. - This isn't a thing. If you live optimally at these temperatures they aren't cold for you as an organism. We like the temperatures our bodies maintain because our chemical reactions go well at those temperatures.

2 A means to cope with their poor atmosphere. -- This isn't a thing. If you live with a thin atmosphere then this would be poor for humans, since we need to breathe oxygen and don't do well with solar radiation, but if you didn't evolve for that then it's not something that matters.

3 Adaptations to survive solar radiation. -- This is a slight thing. In theory high energy stuff can break complex things but oxygen is one of the worst and most destructive things and we breathe it like a boss. And this sounds like a lot of nummy nummy energy.

4 An inner biome to produce food and recycle waste -- All bodies are doing this. That's life's jam. If it's something you can recycle bodies do this. The producing food is a problem. Since you still have to obey the laws of thermodynamics.

You could make it hibernate for like 25 years when the radiation absorbing moss covering its body builds up enough energy reserves to power its bear to the spawning grounds, and all the bear/moss cooperative critters go and have bear babies and moss babies. Or have some additional energy around. Maybe the radiation absorbing moss stuff is optimally adapted for the pole, and can't breed that far south, and only by riding a bear-like creature south and then north could it get successful.

Calling something inhospitable is just wrong without context, things only need energy, beyond that life finds a way. Nothing else from the planet lives there because nothing else can really harvest the energy (whatever energy is has). But, if stuff lives there it's both hospitable and habitable. Things like radiation and heat and cold and atmospheric pressure seem inhospitable because we, as humans, can't live there. An alien that lived there would have no issue at all.

Ps. I used moss as a shorthand for the only radiotrophic stuff I know about from Earth. That went and very quickly took extreme radiation of a nuclear meltdown and turned it into energy. Because, again, these aren't problems. Extreme radiation like that isn't a problem, it's a food source.



I'll divide the answer in two, first how something similar can live on a smaller scale and then where can it take the additional energy to scale up.

Living on smaller scale


I'll first introduce some characteristics of lichens:

Problems of lichens

The first potential problem is the cold, in case that planet is colder than the arctic tundra or in case the changes require this kind of compensation. There are various methods to survive in colder environments, among which antifreeze proteins https://en.wikipedia.org/wiki/Antifreeze_protein for up to -30°C and other substances like https://en.wikipedia.org/wiki/Xylomannan for up to -60°C. Freeze tolerance doesn't seem to be suitable in a planet covered in snow. It'd just stay frozen.

The second problem would be the inability to move, for which I think there are two two possible ways:

  • just have the fungus move. The answer to this question Biology of mushroom creatures says that it's possible and it seem they'd be able to have the behaviors you ask, just not that big due to how it gets its energy (As per eventual additional energy required, it could use the additional energy mentioned above).
  • Alternatively having the mycobiont being a sufficiently small animal instead of a fungus.

The last one is that they take their energy from their surface which exposes them to the square-cube law as by increasing the size, the surface increases like a square while the total cells and the energy they need grows like a cube (unless you have something flat, which wouldn't be much like a polar bear).

Additional energy

Cold fusion

The missing part is the energy to allow it to scale up to the size of a polar bear. My suggestion is cold nuclear fusion.

I know that as a topic it's not well received by most scientists, but even if marginalized there are still various scientists that are currently researching on it (for example this conference in 2019 https://iscmns.org/iccf22/program/ ) including university professors https://en.wikipedia.org/wiki/Yoshiaki_Arata (around 2008) and there are some known ways that could theoretically make it possible https://en.wikipedia.org/wiki/Muon-catalyzed_fusion . I hope that the presence of theoretical possibility is enough as the question wasn't tagged with 'hard-science'.

Nuclear fusion could be powered with just deuterium, which could be taken in large doses from sea water from the habitable zones. Than the organism could use the energy it still retain from the previews time to process the water. At first it could reduce the amount of normal water with something with the same result to what done industrially ( https://en.wikipedia.org/wiki/Girdler_sulfide_process followed by distillation). This is made even more plausible because the required amount of water processed every day would be 68 mL.

Frequency of eating

The energy needed for a polar bear is the equivalent of 2Kg of fat/day https://kidzfeed.com/what-do-polar-bears-eat/ or around 74MJ/day. But this could be much lower as this creature wouldn't need to move as much as a polar bear (if anything it doesn't hunt). Applying the same ratio from active to sedentary as humans https://health.gov/dietaryguidelines/2015/guidelines/appendix-2/ the resulting estimation is 60MJ/day.

A polar bear can take a meal of 50 kilograms. Drinking 50Kg of sea water could be refined in that way to 0.5Kg by removing the non heavy water. In https://en.wikipedia.org/wiki/Heavy_water#Toxicity_in_humans it says that the ratio is 1.1 g deuterium / 32 Kg normal water. This means 1.7 g of deuterium. From https://en.wikipedia.org/wiki/Nuclear_fusion#Neutronicity,_confinement_requirement,_and_power_density it seems that hot deuterium fusion has a specific energy of about 225 million MJ per kilogram of deuterium.

If the hypothetical cold fusion is able to make the organism use 20% of this energy, than it would have 225000 MJ/g * 1.7g * 20% = 76500 MJ. By dividing this by the requirement of 60MJ/day would give us 1275 days or 3 years and half. From this we must subtract the energy needed to refine the sea water and prepare the deuterium and based on my understanding this should be a fraction of what a nuclear fusion would produce. But even giving it half the energy this animal should still be able to survive while visiting the habitable zones only once every two years, which I guess is within what asked.

The remaining problem would be the generation of neutrons and protons, which I guess could be solved by using the same characteristic as https://en.wikipedia.org/wiki/Deinococcus_radiodurans or other internal protections.


The resulting being would need to have some of the properties of lichens, namely the ability to survive out of thin air, but it would need to be able to move and have the size of a polar bear. Additionally for some strange evolution path and coincidences (akin to when life started) it was able to develop the complex machinery and chemical reactions to allow the cold nuclear fusion to happen.

If my estimation are right this organism would need to return to the habitable zones only one day every two years. Additionally the amount of water that it needs to drink each time would justify its size even if the rest of the time it lives in a mostly desert place.

Edit: added cold fusion as energy source and adapted the rest to it. Additionally I fixed the readability of the part about the cold.

  • $\begingroup$ The -60c stuff is for Earth biology. Developed in the oceans moved onto land, then moved into extreme colds. There's plenty of creatures that can freeze completely solid and be fine. And the only reason it matters is that our chemistry that we developed at a core level doesn't work very well at the extreme ends. Throwing in antifreeze proteins only matters if you have water in your body and freezing it the wrong way will break your cells. We put in a lot of evolutionary design work in chemical conversions that kinda need Earth room temperatures to work. If you didn't then you don't need that. $\endgroup$
    – Tatarize
    Commented Jan 1, 2020 at 7:41
  • $\begingroup$ @Tatarize I know of creatures that survive freezing, but that make sense only if you are going to unfreeze in spring, thing that is not going to happen in a planet covered in snow. As per the earth biology, yes, I provided a creature based on earth biology because I know it works. Just saying "alternative biology with lower temperature" is magic, not science-based. I tried to be as grounded as possible with a concrete example, I can't see how that can be a problem. Not to mention that likens already live in arctic tundra, so it shouldn't be a problem anyway. $\endgroup$
    – user71425
    Commented Jan 1, 2020 at 11:18


As others have noted, your big problem is energy. If your surface is cold enough to have a polar climate, then it seems likely that the planet does not receive sufficient irradiation to maintain a large autotrophic animal. However, there are some caveats:

  • A thin atmosphere without significant greenhouse gases + a high albedo surface could allow for significant irradiation + low surface temp
  • Even though Venus is much closer to the sun than Earth, the surface temp would be about -40 C if it didn't have any greenhouse gases!
  • Problem: water vapor is both high albedo and a greenhouse gas :/ On the other hand, it doesn't drive climate, but rather responds to it

There are a couple scenarios I can think of that might power enough handwavium to get you to your goal. At any rate, you should give up on the polar bear body plan in favor of a large, flat creature, like a land-based manta ray. It would ideally be black, because it's absorbing as much radiation as possible, including UV! Think "2-D snake" that moves via gentle undulations that travel across its surface.

Cloud City

The trick is that you want enough clouds to keep the surface below freezing most of the time (or you don't have much of a polar biome), but not so many that your creature starves to death. Instead of flat, uniform cirrus clouds, you want billowy cumulus which are very patchy/clustered and create large spots of cold darkness over the land they pass. A nice feature of such clouds is that they pose an environmental hazard for your creatures. When a cloud passes over them, they either have to burn stored energy reserves, or rest and go into a quiescent state until they get the warming rays of their star again.

The clouds, as mentioned before, conveniently reflect a lot of solar radiation before it hits the surface, preventing the surface from heating up despite high average radiation flux at the planet's orbital distance. But you want just enough clouds to keep the temps freezing, but not deathly cold freezing (ideal average surface temp closer to -10 C rather than -50 C). And they need to be sparse enough that your plantimals can feed regularly.

Tidal Lock

Another idea which can be used separately or together with Cloud City is the idea that the planet is nearly tidally locked with its star. So there are, say, 4 "days" per "year". If it were tidally locked, it would be 1 day == 1 year. With the slow rotation, you have half the planet frozen on the dark side, with the other half balmy on the warm side. Near the terminator (dawn side), you have ice coming into the sun. Obviously, the autotrophs wouldn't venture onto the night side, because that is a desert for them, and certain death (without major stored reserves). But perhaps the polar region persists for quite some time before "thawing out", so you have a nice temperature gradient from freezing-cold to tropical-UV-burnout across the day side.

Axis of Winter

Also, a more extreme axial tilt would also facilitate more extreme winter/summer variation. So maybe it isn't polar conditions all year round, but only most of it. The amount of winter you have and its variation can be controlled by the day length and the axial tilt. Extreme tilt will give extreme seasonal variation, while long days will bring more stability within each longitude. You can tweak these to control the weather on your world. Freezing cold all day every day is probably too much for a walking plant. But even bears hibernate! Your snowmat could do something similar, foraging during spring through fall and going dormant during winter.


While your creatures can get carbon from the air via CO2 (though presumably this is very rare in your atmosphere) and can fix its own nitrogen using symbionts, it will still need to replace elements like iron, phosphorus, sulfur, and lots of trace metals. If the continents are constantly being subjected to freezing/thawing conditions, then you can just say that they sometimes "graze" on exposed soils containing vital nutrients, and absorb them that way. They can also feed on microbes and worms in both the soil and the ice. I don't think the density of worms/algae is high enough to support a mobile animal, so it will only feed on these to replace essential minerals, relying on its chloroplasts for primary energy.


While earth does not receive enough solar energy to support autotrophic animals, your planet might. Most of the plants and creatures on the surface use dark pigments to protect them from radiation damage to their DNA, but your walking plant may actually harness UV photosynthetically via scintillation. Now, coral don't actually harness the reflected yellow light because they are hunters, not plants. And unfortunately, chlorophyll is specialized to absorb blue and red light, not green-yellow. On the other hand, both red and blue-green algae are specialized to absorb yellow and green light. If your creature carries a mix of all of these, it can literally harness the full visible spectrum (though not at 100% efficiency). Some researchers believe that land plants are green exactly because cyanobacteria were the first autotrophs and occupied the green-yellow niche, and that chlorophyll was invented by bacteria that were forced to feed on "greenless" sunlight.

While animals use melanin to absorb UV and reduce radiation damage to DNA, this UV energy otherwise goes to waste. It is probably better for your creatures to use the "coral skeleton" trick to down-convert the UV into visible light. You obviously can't rely on a normal endoskeleton for this. You would want something more like a semi-hard shell, or at least lots of little bony plates near the surface of the skin to act as "UV reflectors" for your creature.

Good luck!

  • $\begingroup$ I'll take not of your explanation on weather condition and rotation axis of the planet. Other than that the shape of the animal may indeed be flat, but it would lose heat that way. Slithering on the cold snow and ice may not be a good idea. Your "coral skeleton trick" is good, however this suggests that the algae would be exposed to the cold. I mentioned in my question that the symbiont is inside the creature to make use of its internal heat. A creature with a glass bottle body might be more likely. $\endgroup$
    – user71341
    Commented Jan 1, 2020 at 23:54
  • $\begingroup$ Ectotherms are commonly called "cold-blooded" and occur in every ecological niche: nature.com/scitable/knowledge/library/…. Even fish that swim near Antartica are ectotherms: esi.stanford.edu/temperature/temperature3.htm. Endothermic mammals are the exception, not the rule. Also, they don't need to be in full contact with the surface. They can have a layer of stiff bristles on their bottom which gives insulation and an air gap, or some similar mechanism. Anything inside the "skin" of a creature is "inside" it. $\endgroup$ Commented Jan 2, 2020 at 0:32

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