If I genetically modified a human to have a foxtail of roughly 1 metre length through the use of handwaved genetical engineering - would this have an effect on his diet?

Of course an additional appendage means that the human would have to eat a bit more to power for example the muscles that are needed to move the tail. I was thinking about this while reading an article about Keratin, which is the main structural material that is used to construct hair. A foxtail of ~1 metre length would add a lot of fur to the human's body, so I would imagine that this slightly skews the kind of nutrients the human would need.

But I don't know if this would have any significant influence on the diet of this human - would it be like an intense craving for certain kinds of food as an essential part of their diet at times or would it be more like a preference to munch an apple every other day, something like a favourite snack?

My goal is to get an idea of how adding one fluffy upscaled tail similar to that of an Arctic Fox would influence my human's diet so that I could estimate the influence of adding multiple tails for my medieval anthropomorphic foxes. You've got to know how to properly feed your troops if you want morale to remain high.

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    $\begingroup$ Human with a tail may prefer snack bars to restaurants. $\endgroup$ Jan 4 '18 at 11:36
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    $\begingroup$ @CongenitalOptimist This is the best non-sequitur comment I've seen in a while. $\endgroup$
    – kingledion
    Jan 4 '18 at 13:50
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    $\begingroup$ I think @CongenitalOptimist was suggesting that Humans with a tail may prefer eating in places that have stools rather than booths or straight backed chairs. $\endgroup$ Jan 4 '18 at 14:20
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    $\begingroup$ As for knowing if you have properly fed your fox-tailed troops, that is easy. Just see if their tails are wagging. $\endgroup$ Jan 4 '18 at 14:58
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    $\begingroup$ Human with a tail might want to avoid foods that make feces sticky. - You might want to slightly modify the structure and activity of the lower intestine to produce drier feces. $\endgroup$ Jan 4 '18 at 18:28

Not noticeably.

While there's a considerable amount of fur on a tail, like all fur it has a relatively fixed growth rate and a maximum length, it doesn't just keep growing the way head hair does on humans. You may find a slight spike in needs for the sake of seasonal hair shedding if you want to go that way, but it'll be minimal and we're so disconnected from nature at this point it's unlikely your humans would get the appropriate hormonal/temperature triggers.

  • $\begingroup$ Interesting take on the seasonal hair shedding. I hadn't thought about that. You mention that there might be slight spikes in needs - which kinds of food would be needed the most if such a thing happened, even if it's just a slight spike? Or would this not have any effect on the composition of their diet? $\endgroup$
    – Secespitus
    Jan 4 '18 at 11:48
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    $\begingroup$ @Secespitus, what you're looking for there is vitamin supplements for a healthy dog coat, it's probably too swamped in commercial products to get a clear answer. $\endgroup$
    – Separatrix
    Jan 4 '18 at 11:50
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    $\begingroup$ FYI even hair will get to a max length and fall out (though there isn't a shedding season like there is for fur). $\endgroup$ Jan 4 '18 at 11:54
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    $\begingroup$ One has to wonder if it would be pubic-like hair :) If I'm not mistaken there are four? three? types of hair on the human body. You could probably have fun in the story with that. (Is it a "new type" of hair? or what.) $\endgroup$
    – Fattie
    Jan 4 '18 at 16:13
  • $\begingroup$ Domestic cats and dogs bulk up and shed on an annual cycle. $\endgroup$
    – Yakk
    Jan 4 '18 at 20:07

Locomotion could be more efficient? Particularly at high speed. Hence, saving food.

Obviously if you run/march more efficiently, you need less caloric intake each day.

Thus, in answer to your question it's quite possible that when moving at high speed a Foxtail would need less food each day.

The general point (as far as we know) of a tail on things like leopards, dogs, is some sort of counterbalance system while moving along at high speed. (Check out awesome videos about this in regard to leopards.)

It's possible that, quite simply, Usain Bolt would be faster over 100 with a tail. And that for conventional joggers, you'd use less energy - maybe much less - over everyday 5ks and 10ks.

Certainly, in a story-telling sense, it would be totally feasible and reasonable to assert this.

(Note that, indeed, human or any animal biomechanics is a fascinating field. Particularly with robotics coming along trying to equal it. The two human gaits of walking, running, are astoundingly efficient. There are some really fascinating results - for example, as any nutritionist / sports medicine person will tell you, when humans run, interestingly they use the same amount of energy per kilometer - it doesn't matter if you run fast or slow; energy use during walking gait is totally different again and interesting in other ways.)

Again, in a story-telling sense, it would be totally feasible and reasonable to assert that adding a tail makes, in particular running, maybe all locomotion, a little more efficient - so you need less food per day!

To put it another way, it's a commonplace thing in scifi that adding a monkey-tail makes it "easier to climb around in trees or zero gravity". Similarly, you could say adding a "balance tail" (think of those leopards) makes locomotion a bit more efficient - needs less energy, can go simply faster at top speed.

Thus, in answer to your question it's quite possible that, particularly when moving, a Foxtail would need less food each day. More efficient locomotion == less calories needed each day == less food needed each day.

Maybe it helps your story!

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    $\begingroup$ I always thought the counter balancing effect with a tail was more for cornering than for running in straight lines. As such I don't see how people would use significantly less energy during a 5 or 10k. Especially when offset by carrying a bit of extra weight in the form of a tail. $\endgroup$
    – Erik
    Jan 4 '18 at 17:39
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    $\begingroup$ Thanks for posting! But, this answer doesn't actually answrer the OP's question, which is about whether or not diet would change. Your answer appears only to comment on the value of having a tail, not whether or not the tail would require you to change diet. Could you update your answer to address the OP's question? $\endgroup$ Jan 4 '18 at 17:40
  • $\begingroup$ Hi @JBH - sorry man, I thought that was very obvious? Need less energy == change in diet. I will put it in explicitly, thanks !! happy new year BTW $\endgroup$
    – Fattie
    Jan 4 '18 at 17:48
  • $\begingroup$ Hi @Erik "I always thought the counter balancing effect with a tail was more for cornering than for running in straight lines" No, absolutely not - not at all. Check it out online - leopard locomotion is highly studied. (Particularly with all the interest in robotic locomotion.) It's inconceivable they could move that fast without their amazing counterweight system. Read all about it! $\endgroup$
    – Fattie
    Jan 4 '18 at 17:51
  • $\begingroup$ LOL thanks @JBH ! You know what they say "ASSUME makes an ASS out of U and ME" in this case I assume too much and made an ass of myself :) $\endgroup$
    – Fattie
    Jan 4 '18 at 17:52

Overall, I think that the nutrient requirements would be proportional to the weight increase, with a slight increase in protein requirments during the annual fall bulk up.

Tails are used for different things.

  • Cats use them as distractors. Get the birdie watching the tail twitch, then SNARK.
  • Canines have a whole bunch of social cues that use the tail. In addition, in cold weather, tails are parked over noses. Dogs like Newfoundlands and Labradors have heavy tails that can be used as rudders and as handles.

Humans are thought to be semi-hairless to shed heat more efficiently. You will need to decide if shaving your tail will help someone keep cool.

You also need to decide how prehensile it is.

Canine tails very often have a white tip, and sometimes lighter fur on the underside. Makes the position easier to discern from far away. Soldiers may dye the tip if they are night fighting. It also can be used for signalling.



  1. Bald people have negligible dietary requirements to people with hair all over their bodies.
  2. People who lose an arm have negligible changes in dietary needs.

...can predict that there would be negligible changes in someone's dietary needs due to gaining a hairy limb.


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