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This is a partner question to How do centaurs get enough oxygen to run

Centaurs are a common mythological figure, with the body of a man where a horses head would be. They usual exist in a fantasy world but lets say they are not sustained by magic but instead by biological processes.

This has obvious advantages in terms of speed, maneuverability, visibility, etc. There is however one obvious problem, they have the small mouth and throat of a human trying to support the energy and oxygen requirements of the massive body of both a human and a horse.

Humans are not adapted to eat grass or grains, however a centaur could potentially have a horse's digestive system so would centaurs be able to live on grass? If they could would they be able to graze? It seems their body shape would be more suited to giraffe-like eating fruit and leaves from trees rather than grazing of grass.

Could they get enough energy that way though given their smaller mouth? Would they need to be carnivorous or at least omnivorous?

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Tim B
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  • They have the combined space of a human body and horse body for lungs+digestion, the only real limit is how fast they can ingest it – ratchet freak Jan 06 '15 at 10:35
  • I think it depends heavily on their intelligence and civilization. If they eat high sugar/high fat foods combined with efficient vitamin/mineral supplements, they should have no problems at all. Humans can easily ingest their required daily nutrition in a few minutes if they use junk food and vitamin pills. (The long term effects of such a diet might be bad, though) I think it's more about WHAT they eat that determines how it would go. – Erik Jan 06 '15 at 11:00
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    Many humans, with small mouth and throat, are obese. This means that they can get much more energy than required by a human body. – mouviciel Jan 06 '15 at 14:07
  • @Erik Junk food may not be necessary... – Superbest Jan 06 '15 at 20:55
  • If your centaurs don’t have to live on actual Earth, but a fantasy world, make them depend on fictional high-energy fruits from certain trees that birds cannot digest and most other mammals couldn’t reach. In Greek mythology this could have been ambrosia, but I’m not sure what these original centaurs were actually supposed to feed upon. – Crissov Oct 16 '15 at 09:22

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A 1000 pound horse needs approximately 15,000 calories a day for maintenance, the average 160 lb human needs around 1800. Take 70% of a horse and 50% of a human, that gives you about 11,400 calories per day as a maintenance level. (Pretty much just breathing in and out).

A typical McDonald's meal (Quarter pounder, fries, non diet soda) runs in the neighborhood of 900ish calories, so a centaur to just exist would need to eat around 12 Quarter Pounder meals a day just to subsist.

While in the oxygen question there is the benefit of being a poor utilization ratio, the body is actually pretty well versed in conserving calories, and is very efficient (Which is one reason it's so easy to become overweight).

I would presume that a centaur diet would need to be high in fats, as fats carry 9 calories per gram, while meat/carbohydrate each weigh in at 4 calories/gram. For example, an avocado (21 grams fat) has 230 calories, a 146 gram serving of turkey (Same as the avocado serving) has 152 calories, and typical steak at 146 grams (5 oz) is around 400 calories (depending on fat content, lean meat has less calories).

So, a pound of steak comes in at 1200 calories, a pound of avocados comes in at 700ish, so if those were the only two foods available, you would need about 6 lbs each of steak and avocados per day to reach maintenance levels.

The average American I see chowing down manages to get through 900 calories in about 15 minutes at McDonalds, so I would guess that centaurs would need to eat for 1/2 hour to an hour 4-5 times a day to get their needs met, more if they are adapted to make better use of plant material than humans.

JohnP
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    +1 just for being something more than unbridled speculation. – KRyan Jan 06 '15 at 18:53
  • An excellent answer, just the sort of information I was hoping for. :) – Tim B Jan 06 '15 at 19:07
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    @KRyan +1 for clever pun – Michael Jan 06 '15 at 19:27
  • Let's be clear: A 1000 pound horse needs 15 million calories a day. – Christofer Ohlsson Jan 07 '15 at 14:49
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    @ChristoferOlsson - Yes, the basic calorie is 1/1000 of a Calorie. However, on food packaging everything is represented in kcals, and most people just see it as 200 calories and that's how they understand it. – JohnP Jan 07 '15 at 14:52
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    Michael Phelps routinely ate 12,000 calories a day while training for the Olympics: https://www.google.com/search?q=michael+phelps+calories – mskfisher Jan 07 '15 at 17:46
  • @mskfisher - Yeah, I swam competitively, you can burn through a lot of calories, especially if you have full day workout regimens like that. Guarantee that's not his retirement load. :) Also look at the calorie loads for cyclists during the major tours, things like that. It's staggering. – JohnP Jan 07 '15 at 17:55
  • Sumo wrestlers eat 8000 calories a day so 15,000 is not impossible. – Fred Dec 07 '16 at 07:10
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    @mskfisher In short, he ate like a horse. – SurpriseDog Nov 15 '19 at 01:54
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Since Centaurs are intelligent and have arms they can raise and collect a much larger array of foods than a horse. I would also expect them in general to have proportionally larger mouths with larger molars for helping ingest the tougher plant tissues.

While a human can survive on bread and water for a very long time, other foods would keep them much healthier. I imagine that Centaurs would eat quite a bit of fruits and vegetables and nuts having a higher calorie content, even though they could 'survive' on grasses and grains.

Omnivorous? Possibly, though I would expect the animal protein to be primarily seafood or birds, more like a vegetarian vs. a Vegan.

Carnivorous? Very unlikely, Carnivores tend to be smaller than herbivores and a Centaur is pretty big and would require a LOT of meat to itself going.

bowlturner
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    A centaur (using a horse for size) is smaller than a dinosaur, a polar bear, or an orca. Size doesn't appear to be a good argument on why centaurs cannot be carnivorous. – March Ho Jan 06 '15 at 15:03
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    The carnivorous dinosaurs were not the largest. The polar bear is the only bear that isn't omnivorous, and this is likely because there isn't anything but other animals for it to eat in it's habitat. A carnivores size is dependent on the size of it's prey. Solitary hunters are larger, pack hunters are smaller (than their prey). – bowlturner Jan 06 '15 at 15:26
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    http://en.wikipedia.org/wiki/Baleen_whale#Diet – March Ho Jan 06 '15 at 17:17
  • Nice one. How about land based carnivores? – bowlturner Jan 06 '15 at 17:20
  • Doesn't meat have a higher energy density than any other type of food? Meaning wouldn't you have to eat less meat than grains/fruits/veggies to get your daily caloric intake? – James Jan 06 '15 at 19:16
  • @James I think your right. – bowlturner Jan 06 '15 at 19:25
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    Spinosaurus were the biggest carnivore at 8 tons. Whereas the sauropods (vegitarians) weighed in at double that. – crthompson Jan 06 '15 at 20:34
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    This comment thread seems to boil down to "animals come in lots of different sizes" – Dancrumb Jan 06 '15 at 22:00
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I mentioned birds in my other answer so why not here as well,

Using a gizzard centaurs would be able to digest fibrous foods that humans wouldn't be able to. Then allowing the food to be fermented in a rumen stomach would allow the remaining digestive system to get more out of the plant matter. (breaking down toxins as needed)

Having dexterous hands would allow them to get to food that other animals would have a hard time getting behind spines or in burrs/cupules.

ratchet freak
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The subject of centaurs eating was (briefly) addressed by C.S. Lewis in The Chronicles of Narnia. In that world, centaurs had two stomachs, one human and one equine, and had to eat to fill both, which meant that they ate a lot, both human and horse food, and spent some time doing so. (ref) Though the mechanics of how they grazed was not mentioned, as far as I remember.

Another point is that, depending on the world, the "human" portion of the centaur may not actually be human-sized, but instead sized proportionately such that the torso of the human half is the same size as the neck/torso joint of the horse, so "small mouth and throat" might not be applicable. - Again, in Narnia, the human portion of the centaur was compared to giants, rather than normal humans. In Nick O'Donohoe's Crossroads series the increased size of the human half of centaurs is also explicitly referenced. (Though their dietary needs aren't mentioned, if I recall.)

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user5285
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    There is another example in the first of the "World of Tiers" books by Philip José Farmer. It's been a few years since I read them, but if memory serves they have a largish torso and head allowing for a large mouth. They are carnivorous as well. – Tonny Jan 06 '15 at 19:50
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I cannot imagine centaurus to be ruminant - chewing the cud all day in the shade? Just the opposite, centaur would be much better hunter than humans are.

Also better farmer: plowing the fields would be easier.

My bet is carnivore like neanderthal man, diet is mostly meat with fruits, cheese and grains added. Just eats three times as much as average human.

Peter M. - stands for Monica
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