I'm designing an earth-like planet with a relatively similar biosphere to earth's. The explanation I have for the close parallels is mostly a hand-wave: This planet and earth are linked by a number of wormhole-like structures that randomly exchange material from one planet to the other. The exchange of living organisms has affected the development of life on both planets.

This planet has dragons (or perhaps I should say 'dragon-like creatures', since in my attempts to make them somewhat more realistic I've nerfed many of the traditional dragon-y characteristics). They are intelligent, but are naturally solitary and therefore do not usually form any kind of societal structure. They are around twenty feet long as adults (though they can grow somewhat larger), are lightly built, and are omnivorous (with a predisposition toward being carnivorous). I'd prefer for them to be warm-blooded if possible; however, if being cold-blooded makes more sense, I'll go with that.

So, given that background, would it make sense for a solitary dragon of the kind described above to raise an herbivorous mammal comparable to a goat as a food source (as compared to the obvious alternative of simply hunting for suitable prey items)? Also, if this is viable, what would the ideal breeding population be for such creatures (again, goats are for all intents and purposes an accurate substitute for these animals)?

  • $\begingroup$ Can your dragons build fences? $\endgroup$
    – Jasper
    Sep 30, 2019 at 20:19
  • $\begingroup$ Though it requires some reworking, I came up with a plane to further reduce a dragon's metabolic needs. Dragons in my setting have scales that are somewhat resilient to gunfire. These scales have a foamy internal structure to maximize the strength-weight ratio. Because of this, they double as heat insulators, since they cover the entire body, except the wings. The leathery wings would provide huge surface for the dragon to take up heat with and could be folded if it' gets colder. With the insulation, this can prevent heat from escaping. $\endgroup$ Oct 2, 2019 at 12:46

4 Answers 4


There's a significant difference in the caloric needs of endotherms and ectotherms. Large reptiles that regulate their temperature externally can often survive on a single, large meal per year, where the largest endothermic omnivores eat every day, with the exception of when they hibernate. Think Nile crocodile and brown bear.

Other issues are that the crocodile has to live in tropical and subtropical regions where there is enough heat to keep it alive, while the bear can live pretty much anywhere. The crocodile also lives a very sedentary life, except for when it's eating and mating. Herding goats would require a greater expense of energy, which would in turn require more goats to be consumed, and thereby necessitate a larger herd. It wouldn't be worth it -- easier just to find one big goat a year and eat it.

For the bear, it's a different story. Needing to eat a big goat every week means he's in danger of starvation every week if he doesn't make that happen, so maintaining and defending a herd is a safer option.

As far as the goats being afraid of the dragon, that's a non-issue. On earth, goats have a natural fear of wolves, yet domestic dogs, which are a type of wolf, are used in two ways to work goats (and sheep). Herding dogs use the goats' fear of predators to control their movements on the pasture, while livestock guardian dogs (LGDs) are raised with the goats and the goats learn not to fear them. (Note that herding dogs and LGDs are not generally used together, as the LGDs, like the goats, would view herding dogs as predators and would kill them.) The goat can be conditioned not to fear any animal, and it's likely that beyond a certain size threshold, an animal would stop looking like a predator and start looking more, to a goat, like a large herbivore, since the largest animals on earth are herbivores, and it is not uncommon for goats and other mid-size grazers to share the pasture with larger animals, in captivity (horses and cattle) and in the wild (buffalo, rhinoceros, etc.)

Also bear in mind that in both ectotherms and endotherms, the larger the animal gets, the greater its volume to surface area ratio, which means that its capacity to maintain body temperature increases and its caloric needs per unit of mass decrease. Since body heat is lost through the skin, the less skin you have in relation to your thermal mass, the less heat you lose. In other words, it takes fewer calories to sustain a pound of elephant than it does to sustain a pound of mice.

In my experience a 500 pound tiger or lion eats about its own body weight in meat every month. Since some of the mass of the prey animal is bone, probably 30% on average, we can say that a 500 pound cat would need 7 or 8 100-pound goats per month.

I'd estimate the weight of a 20-foot dragon at 4000 pounds at the absolute most. Since it takes less food to sustain a pound of dragon than a pound of tiger, the number of goats required per month might be something like 35-40 goats per month. That means a minimum herd of about 500 does, to be safe, unless you go with a large breed and allow significant time for them to grow. It's a lot of goats and would require a lot of real estate. This is based on 100 pound goats at time of slaughter. You can raise them larger, it just takes longer for them to get to that size.

Cattle range as heavy as 3000 pounds, though 1500 for a steer at slaughter is more typical. Fewer animals to manage, but they still breed once a year, so you have to maintain a large number of animals all year long.

Rabbits reproduce every month, and can give birth to a dozen kits every time, and can reliably raise 6 kits to weaning time. Pound for pound, they produce the most meat with the least feed of any livestock, because they are so prolific. If I was inventing animals, for this purpose, I'd make them like very large rabbits, maybe something like a capybara, with the rabbits reproductive cycle. Or just invent goats that breed like rabbits. Of course, the larger an animal gets, the slower it grows and matures, and that means longer gestation too. You could compensate by having your giant rabbit only give birth to one offspring at a time. That way, a herd of 50, 100-pound rabbits might be enough to sustain a 4000 pound dragon.

Also, consider giant chickens. Then your dragons can have eggs too.


Depends on two things: one, how intelligent your dragons are, and two, how non-threatening they look to your goats.

Are your dragons the human analogue of your planet, or are they a threat to some other species that is a closer human analogue? Can the dragons speak to each other or to the humans with the complexity of human language? If they can, they're probably clever enough to figure out how to keep a herd of their favorite food captive, or at least learn how to do it from others. If they are not, I wouldn't count on them building fences anytime soon, but I could see them being smart enough to keep tabs on one or two wild herds in their territory and take steps to keep them within the territory, such as scaring them away from boundaries or creating obstacles like trenches or felled trees. This latter case would be much more like standard hunting (just with "their own" pet prey) than like proper domestication, but I'd say it's valid.

Complicating the matter is the fact that your goats will likely be terrified of your dragon, if the dragon is as large as you say and looks and acts typically dragon-ish. They will know the dragon is a predator out to eat them, and unless your dragon has some way to make itself seem like a friend, it will have a hard time doing any proper domestication of them. To avert this, it may be worth considering possibilities for a symbiotic relationship. Perhaps the goats trust the dragon because the dragon gives the goats something: a home, protection, warmth, a nutrient or treat of some sort, safe breeding grounds? The bottom line is that for the goats to trust the dragon, they need to get something out of it that is worth members of their herd dying when the dragon gets hungry. Maybe the dragon helps them harvest a certain type of fruit that is a much more efficient energy source than grazing but grows too high up in trees for them to reach, for example. There's room for a lot of cool speculative symbiotic evolution if you take this route.

  • 1
    $\begingroup$ I suspect that in the process of domesticating the goats for breeding the dragon could also select for lack of fear of dragons. We've been raising and slaughtering goats for ten millennia and they aren't particularly afraid of us. The dragon protects the goats from predators and provides them a safe place to graze. $\endgroup$ Nov 9, 2015 at 6:08

If your dragons are smart enough, you can definitely have a drago-shepherd caring for his flock while playing his drago-flute.

As for breeding pop, you'll need to provide us with the size and weight of your average adult dragon and the pop size of your dragon tribe.

You can compare with dinosaur sizes/food consumption at Wikipedia or here: https://what-if.xkcd.com/78/

I'd go with cows for large dragons, or maybe elephants?

  • $\begingroup$ +1 for elephants! Even cows, if domesticated by intelligent Dragons wouldn't have been pressured into a smaller domesticated size. $\endgroup$
    – Jontia
    Oct 1, 2019 at 8:41

Make the herd animals intelligent. The dragon guards the herd from predators in return for a monthly sacrifice that dragon uses as food.


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