So, I'd love to have werewolves in the world I'm building, but as it's a sci-fi setting I don't really want them to be magical. I can stomach some pseudoscience, but I want the process to be as realistic as possible. To this end, I've removed the influence of the moon (it's just a cyclic transformation, happens based on an internal clock), silver bullets and holy water don't have any special potency, and I'd be willing to extend the transformation from man to werewolf to an entire day, or even a week if necessary. What I'd like to know now is what sorts of preparations a lycanthrope would have to go through in order to make this transformation seem plausible, if not entirely possible.

For instance, what would someone have to eat to support an increase in size, a reconfiguration of bone and muscle structure, and an extensive growth of hair? What sorts of exercises or therapies might be useful or necessary to help people through this painful process? Are there perhaps any good examples of animals that do something like this, and how do they prepare for it?

  • $\begingroup$ If you've ever broken an arm, you know how long it takes for even tiny amounts of bone to grow. Growing larger bones (especially the skull and teeth, both of which would have to enlarge significantly) would take months to years. You're going to have to stretch reality (no pun intended) to get down to a week. $\endgroup$ May 13, 2015 at 18:53
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    $\begingroup$ Perhaps a reality-check tag would be more appropriate than science-based? $\endgroup$
    – Seth
    May 13, 2015 at 19:02
  • $\begingroup$ @Seth I already know and accept that it's impossible, what I'm asking is how it can be made more plausible. Perhaps the science-based tag is out of place, but I don't know how else to ask for what I'm looking for. $\endgroup$ May 13, 2015 at 19:04
  • $\begingroup$ A wolf is going to weigh significantly less than an average human, so someone undergoing the human->wolf transformation would have to get rid of excess weight, or wind up as a really obese wolf. $\endgroup$
    – jamesqf
    May 13, 2015 at 19:11
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    $\begingroup$ @DaaaahWhoosh: Not really familiar with any of those. I suppose my mental image of a werewolf is highly colored by Angua from Discworld... $\endgroup$
    – jamesqf
    May 14, 2015 at 7:10

8 Answers 8


Science (not pseudo) is identifying that certain genes are active in different parts of the year. Most recently: Seasons May Tweak Genes That Trigger Some Chronic Diseases (When I say recent - that's from May 12th, 2015 and today is the 13th).

A study involving more than 16,000 people found that the activity of about 4,000 of those genes appears to be affected by the season, researchers reported in the journal Nature Communications. The findings could help explain why certain diseases are more likely than others to strike for the first time during certain seasons, the researchers say.

If one wanted to stretch this, the combination of a virus (inserting genes) and a monthly trigger of the expression of the genes inserted by the virus would not be that far fetched at all.

The transformation, again stretched from what is present in reality, isn't implausible either. Plants such as the Venus fly trap can demonstrate very rapid growth in a very short time (it is rapid swelling of the existing cells). Other mechanisms could include very rapid growing tumors that are rapidly consume stored energy (accumulated over the course of a month) to grow. Upon the conclusion of the night (a wonderful time to bite and spread the virus), the cells would experience apoptosis (the virus doesn't want to cause its host to die from the prolonged depletion of energy that the tumors would demand) - except for the cells that start the next cycle.


If you want something vaguely plausible in a scifi setting then you might go with a chrysalis. Every month would be far too fast and the change happening in a week would require high-scifi stuff like nanotech for anything the size of a human but you could have some kind of vaguely biologically plausible cyclic transformation if you allow more time.

You could probably spin it as some kind of parasite which causes the transformations which eventually reverts you to human form to hide as part of some kind of cyclic lifecycle. This also gives you an excuse to make your werewolves immortal like Turritopsis dohrnii.


The human ages and at some point feels a massive urge to eat. They fatten up then feel the urge to find somewhere secluded where they curl up and exude a chrysalis. A few months later your werewolf crawls out. Drama happens with wolf form and others are infected and eventually the wolf form feels the urge to find somewhere secluded again where it pulls the same trick to turn back into a youthful human who crawls out with vague memories of doing something terrible.

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    $\begingroup$ This is not at all what I was expecting, but I really like it. $\endgroup$ May 13, 2015 at 19:07
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    $\begingroup$ I've never heard that we have any real understanding of the metamorphic process. If so, you could spin your own rules without being considered unrealistic. $\endgroup$ May 13, 2015 at 20:31
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    $\begingroup$ It could be a derivitive of technology developed for rejuvination. It was tried on other animals first, so profiles are available for dogs and other mammals. Someone thought it would be cool to turn himself into a wolf (bio geeks...) and had no idea that he was contagious. $\endgroup$
    – JDługosz
    May 13, 2015 at 23:31

Requirements for Transformation

In order to perform this transformation in a relatively short period of time a day, our lycanthrope is going to need a lot of calories. A lot. Consider that active male teenagers are well known for consuming impressive quantities of food on a daily basis while undergoing their growth spurt, a lycanthrope about to undergo a transformation will have similar caloric needs in a vastly compressed time frame.

Calcium & Phosphorus Requirements for Bone Growth

According to this article, the ratio of calcium to phosphorus is 5:3. If between the ages of 10 and 20, the average human male accumulates about 17 pounds of bone to achieve a height gain of 15 inches, that means our lycanthrope needs to consume 0.5 lbs of calcium for each inch of height gained. This quantity doesn't account for any increases that might be required for increased bone strength as a result of the cube-square law. Please note that 0.5 lbs of calcium is just for structural growth. Calcium is also an electrolyte so you'll need extra to counteract losses through sweating or urination. In terms of food consumed to get this much calcium, assuming a dry skeleton is 20% of total body weight, our lycanthrope will need to eat the bones of two chickens for each inch of height he grows.

Protein Requirements

Speaking of chickens, a 140 gram (5oz) chicken breast offers 43 grams of protein. For each inch a human male grows during puberty, he gains two pounds of muscle. Since muscle is approximately 80% water, each inch of growth requires 181 grams of protein (and 726 grams of water to hydrate the muscle (about a 3/4 liter)). The lycanthrope must eat four chicken breasts to get sufficient protein to grow an inch. In addition to the chicken breasts, he will need to drink half a liter of water just to hydrate the new muscle.

Ha! This is working out nicely, each inch of growth for the lycanthrope equals two chickens for calcium and protein. Better eat the whole chicken though instead of just the breasts because dark meat has lots of fat in it.

Digestion Caloric Intake

Each calorie a human consumes carries a 10% digestion cost so all of our estimates thus far will need to increase by that much.

Maximum Temperature

Brain damage in humans happens when body temperatures go above 107°F (41.6°C) thereby setting an effective limit on metabolic burn rates. Elevated body temperatures may inhibit some metabolic reactions (though I'm not biochemist so I can't say for sure). Increased body temperate means lots of sweating, so he will need even more water and electrolytes just to stay alive.

Thermal Output of Growth

To simplify calculations, let's assume the lycanthrope is just a water bag weighing in at 100 kgs at 35°C. Note that a nutritional calorie is 4.2 kilojoules. To raise the temperature of one gram of water by one degree Celsius takes 4.179 joules. Assuming no heat loss, the lycanthrope has a 2.7 megajoule heat budget going from 35°C to 41.6°C. (I'm going to ignore natural heat loss through radiation or sweating. My physics are not that strong.)

Let's say our lycanthrope is going for 2 inches of growth for this transformation. That's four whole chickens or 6 lbs of which only 30% is protein, fat or bone. We need to digest 1.8 pounds of raw materials. To make calculation easier, I'm going to assume a uniform digestion cost of 0.7 calories (2.94 kjoules) per gram. (Fat yields 9 calories or 37.8 kjoules per gram. Protein yields 4 calories or 16.8 kjoules.) 1.8 pounds is 816 grams. 816grams * 2.94 = 2.39904 megajoules, or just under our heat budget of 2.7 megajoules.

Keep in mind that this thermal output is just for digestion and does not include basal metabolic rates or the cellular work required for transformation. Regrowing bone and muscle is expensive so I would expect increased energy costs to do it.


Eating two chickens plus other foods plus drinking enough water is going to be a severe test of digestion. Buffering the minerals, fats, and proteins for use during transformation will also be difficult as the circulatory system can only hold so much. Reconfiguring muscles and bones in a day or so could be possible but growth that rapid is akin to extremely aggressive forms of cancer. In short, our lycanthrope is going to be a hot, sweaty, greasy, stinky, comatose mess during the transformation. From his perspective, it will feel like every bone is broken and every muscle will have third degree muscle tears. So either he gets really lucky with his transformation where it completes and he's completely healed or it's gonna take a few days/weeks to recover. Also, the lycanthrope can't eat solid food while transforming because his jaws may lack the strength to actually chew.

So yeah, it's possible over a period of weeks but it's gonna be really really really uncomfortable. Transformation in less than a day isn't feasible.


On this Answer I mused about science-based transformation details.

For plausibility, nanotechnology is the magic word. He can't change mass or transmute elements, but could re-arrange atoms in the extreme case, or be put together with rapid transformation in mind so tissues can be reconfigured rather than rebuilt from scratch. He might look like a man/wolf on the outside but have some funny features on the inside, if he was examined medically for example. Bones might be modular, breaking and joining to form different lengths, or telescoping and not made of bone at all. Muscles might split into different bundles and re-attach to different points, without having to grow different muscle tissue.

Different "brands" might stress different feature trade-offs. One group of enthusiasts might want rapid on-and-off transformation, or prefer "wolf-man" anatomy rather than full anatomic wolfness; others might go for the most authentic anatomy possible and need special IVs to aid the transformation.

A problem with full anatomically correct transformation is brain size. If people are all simply ephemeral arrangements of nanotech utility goo and actually live in cyberspace, they could rez-up any kind of body they want at the moment, at any location in the world.

If the physical brain is altered with nanotech, it could very well be smaller while still being the same architecture. Not modifying the brain, however, makes it much more plausible for a near-ish future nanotech world. That could be an issue, as the head would need to be large and have a large enough brain case not just in total volume but to allow the human brain to fit shape-wise.


My suggestion would be cybernetics, that would allow you to transform almost at will and also explain the increased strength and resilience of the creature.

Imagine a wolverine-like metallic skeleton attached to or replacing the humanoid one, along with artificial muscle to reinforce the human ones and metal plating to defend the vital organs. Normally the enhancements are mostly inactive and beyond being a little heavy you look like a standard human.

When they engage though bones telescope and expand to increase reach and leverage, close combat claws extend from the fingertips, and the jaw expands and metal fangs extend there for additional close-combat potential. Muscle that is usually coiled up stretches as the bones extend while the skin opens up revealing previously hidden folds.

The newly exposed skin is covered in metallic wires that extend out to cover the body and provide some defense against electrical and ballistic while also being insulating (they also look like a lot like fur).

There you go, instant cybernetic werewolf :)


Vast and varied are the environmental triggers for the expression of genes, so the door is wide open for you. Histones are structures which expose sections of the DNA to the rest of the nucleus for purpose of producing specific proteins. Many online resources source old text and incorrectly label the nucleus as the 'nerve center' or 'command center' of the cell. This is completely incorrect. The nucleus is more like a sex gland with a harddrive. Actual processing is done across the entire cell, and mostly in the cell-wall. Anything which can affect the cell has the potential to trigger the Histones to 'allow' the production of proteins. DNA also contains information on what conditions trigger which histone state, and its these 'conditional' genes which will ultimately influence over an organism's morphology.

Human DNA probably already contains all the information needed to produce lychanthropic forms, all they lack is the proper 'triggering' mechanism. You're looking at an organism-wide alteration of morphology at regular intervals, which means you're going to have to, suppress, inhibit, or otherwise override the existing genetic conditional modifiers, and then you're going to introduce NEW conditional statements.

Genetic engineering would allow lycanthropy to be a hereditary trait, the first generation would probably be conceived in a lab and and finding surrogate mother might whose body wouldn't reject the fetus could be difficult. Simply gene splicing wolves and humans won't do. You're looking at an extensive, horrifically clinical trial period while your geneticists develop and perfect their brood.

If you want the condition to spread virally, the virus would be similarly engineered, except the trial 'participants' don't need to be grown form birth and so your research could progress faster.

The implementation of Nanotechnology would be identical to the virus. The difference being the potential to 'program' or 'hack' the triggering mechanisms (if you can find the drivers!).

I would opt for a slow, steady, more fluid and cyclical change. Our werewolf would be more 'human-like' during the new-moon, and more 'wolf-like' during the full-moon, and in some transitional form during the waning and waxing. I'd say the dietary requirements of maintaining a transformative state as roughly proportional to a propetually-stoned-teenager.


Upon reading the question, my first thought was the same as @Murphy - a chrysalis form that converts between the two. While that stage of life is still not entirely understood, the vast change in forms is clear.

As for science, there are biological ways that this could happen, especially given our rapidly increasing understanding of genetics over the past few years. Some combination of altered Hepatocyte Growth Factor Activator (HGFA) (also here) activation/expression, stem cell activation, imaginal discs that the creature has at birth. There are a whole large variety of cell groups, cell types, and gene expression that could account for this type of thing. A vastly enhanced or evolved homeobox, perhaps?

The funny thing about genetics is that it follows the old saying "the more we know, the less we understand." And also "truth is stranger than fiction." The past few years have seen scientists create new DNA "letters" (Floyd Romesberg and team), how endogamic groups have specific markers in their DNA, which could include lycanthropy (why not?), really just all manner of interesting things.

So, from a science-based tag, no... because it's not something we have any tangible evidence of. From a reality-check perspective, it's not implausible at all.


here are alot of great idea's here so i wanted to post my own.

The only realistic one to me is the hybrid form. As a complete change of body plan is not workable in biology.there for your werewolf most remain humanoid. The way i would do it would be a a mix of stem cells cancer and virus all in one. This metamorphic cells or meta cells for short destory the human cells and replace them with the hybird ones in a form of cancer like repeated growth.this combined white hand ,leg and face boons made to come apart in to platelets and reshape in to claws legs and a muzzle .that gets you most of the way.

The real hard part is paying the energy cost for the transformation. It would be huge and need vast amouts of bio mass. But you could get around this by haveing the werewolf store enargy as ATP in vast amounts. This is like storing fat only more effective.

So what you have would be a larger , heavyweight human
with high body temperature and crazy appetite. Then as a repose to strace hormones wold trace form in to a werewolf like monster.

The side effects would be crazy alsome like things cooking and burning 🔥around the were wolf when tracesforming do to ATP porbouseing heat and the huge amount need to transform. thay would uncontrollably eat everything when trasformed do to the huge amount of enargy need to stay alive plus exstra to change back.

How change back works would be the stame Mate cells . when the heman cells were destroyed /replace there dna replaced the hybird bna with in the meda cell. So when the hormon levels go down and there is the enough ATP with in the body the werewolf would change back.

This maens that werewolfs would be not beable to tracefrom unless will feed and would beunable to change back until will feed. The transformation could be at will or a danger fight or felt thing. Brain were wolfs would change uncontrollably and die vary qickly. (Hours at most)

If you want the full moon thing you could say that werewolfs most transform mouthly or there body would over hate killing them bo to stored ATP reasing the body heat.

In combat werewolfs of this type would be faster stronger and able to heal super quickly . plus there claws could beused in human form and thay would be uneffect by exstrame cold.

Some side notes Tails

If your were wolfs have tails then thy would be prehensile tail as humans carry porment bna already for prehensile tail. This also maens thy would have tails in human form as will but most like there remove at burth to blend in with humans bether .

Hair The hair all over the werewolfs body could be a side effect of the high metabolic resporashion need for there trans formashion as keratin the porten hair is made form uses byproducts of resporashion in its make up. Meaning change back would creat more hair and lead to alot of shading.

Think skin Were woulds could have exstreamly think skin makeing them hard to cut or burn bo to the body reuseing keratin in the skin created when transforming.

Armer werewolf

Werewolfs would ether a offout or sub spaces of human and could have sub spaces of there own. One cold have bio armor instead of hair all over its body as keratin is used to make boon horns and other hard biological materials.

  • $\begingroup$ Please proof read your posts and try to fix all the errors and typos. Also, add images if they bring value to the post. Not just for the sake of it. Lastly, I don't see how you are answering the OP's question. To me it looks like you are restating their question. $\endgroup$
    – L.Dutch
    Nov 11, 2018 at 16:41

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