In this video, CGP Grey lays out four criteria which determines whether or not an animal can be domesticated:

• Feedable. You need a bunch of grass to feed one cow, but you’ll need a bunch of cows to feed one tiger. So you domesticate herbivores, not carnivores. (And the herbivore shouldn’t be a picky eater.)
• Friendly. Whether carnivore, herbivore, or omnivore, you need an animal that isn’t dangerous, panicky, or both.
• Fecund. You generally want animals that breed a lot, and you absolutely need animals who will breed in captivity. They also need to reproduce frequently enough that you can selectively breed them to effect over the course of a single human lifetime.
• Family Friendly. Animals that have a social hierarchy lend themselves to domestication because we can exploit those instincts in order to herd them and lead them.

You can cheat a little bit around the edges here and there, but you basically need all four of these things to be true in a single animal in order to make it a candidate for domestication, which is why — despite there being thousands and thousands of animal species on this planet — we’ve only domesticated about fifteen or so.

(We can also domesticate plants, but for the purposes of this essay I’m largely going to ignore that.)

When it comes to worldbuilding, however, something interesting happens in fantastical settings: Magic can bypass — often trivially bypass — these barriers to domestication.

For example, in the real world we could never domesticate bears: They’re feedable (in practice, up to 90% of a bear’s diet is actually planet matter). They’re fecund (having litters of two to six cubs every couple of years). They have a family hierarchy you could hypothetically take advantage of (positioning yourself as the Mama Bear).

But it’s just too easy for humans to become tasty bear snacks.

With magic, though, you could employ charm or even dominate effects to avoid becoming a bear snack while selectively breeding your captive bear population for tameness so that, eventually, you would no longer need to use the magical effects.

This is also a good time to briefly discuss the difference between taming an animal and domesticating it: An animal is tamed when it is behaviorally conditioned to safely cohabit and even work with humans. An animal is domesticated when a population becomes genetically modified to have a predisposition towards and advantage for humans.

So with some fantastical elements of magic, alchemy, or genetics, you can just bypass this entire discussion by waving your hand and saying something like, “I’ve magically altered the creatures so that they and their descendants are instantly predisposed to humans.” But, in my opinion, taking the longer path has a distinctly different feel to it — it feels more societal, rather than mad scientist. (Your mileage may vary.)

In any case, you can see how magic and megafauna can give food security that historically didn’t exist for our ancestors; mitigate the risks from otherwise dangerous animals; or, as with the bears, make them subservient in the absence of a natural hierarchy.

Magic could also speed up breeding cycles, but that’s not even necessary if your fantastical setting includes long-lived species. Elephants take too long between generations for a single individual to selectively breed them and reap the benefits? Not if the breeder is an elf.

EFFECTS ON THE CREATURE

At this point we’ve more or less given ourselves permission to take advantage of the entire animal kingdom, simply asking ourselves how a domesticated (and/or trained) version of that animal might prove useful:

• Mercenaries with war bear auxiliaries.
• River barges pulled by domesticated dolphins.
• Zebra mounts.

With a sufficiently decadent civilization, it doesn’t even have to be that useful, just aesthetically pleasing:

• Hummingbird messengers.
• Giraffes bearing noble palanquins.
• Songbirds providing orchestral performances.

As we’re considering these almost limitless possibilities, it might also be useful to keep in mind the effects that domestication can have on the animals themselves: We made pigs larger, engorged cow udders, and added almost ruinous amounts of fluff to our sheep. So you can always ask yourself, “What if this… but more?” (Or less, if that’s appropriate.) Not just zebra mounts, but zebra ponies and draft zebras, too.

It’s also notable that the mere act of domestication itself can apparently have an effect on a creature’s appearance. For example, in the mid-20^th century Soviet scientists began a multigenerational experiment (still ongoing) to domesticate wild foxes. They did this strictly by selecting the tamest foxes in each generation and breeding them.

Selecting for tameness alone, however, also resulted in the domesticated foxes gaining:

• curly fur
• multicolored coats
• floppy ears
• shortened, curly tails

So could we imagine domesticated bears with floppy ears and curly hair? Yes. Yes, we could. And absolutely should.

EFFECTS ON THE WORLD

When you introduce a fantastical domestication, deepen its connection to your setting and fully integrate it into the campaign world by coming up with at least three distinct impacts the domestication has. For example, domesticated chickens mean:

• Chicken coops exist where they’re raised.
• Eggs are served at breakfast.
• Criminals were punished by tarring and feathering them.

And that’s obviously barely even scratching the surface, but if domesticated chickens didn’t actually exist, it would give us a good start at reflecting their presence in the world (even in scenes where there are no chickens directly present).

So if we had merpeople domesticating sharks, we would want to similarly have:

• Necklaces made from shark teeth as a popular fashion item.
• A military academy where shark-riders train and bond with their mounts.
• Shark races with circuits running through underwater grottoes.

And so forth.

NON-HUMAN DOMESTICATION

On that note, let’s remember that we’ve defined a domesticated animal as one that has been genetically modified to have a predisposition towards and advantage for humans.

But in a fantasy world, humans aren’t the only species capable of domesticating animals.

Thus, for example, our merpeople domesticating sharks in ways that land-bound humans would never be motivated to do.

What would dwarves find uniquely useful? Perhaps a bioluminescent worm to serve as their light and tunnel companion?

What about a lich? What needs do the undead have that humans do not? Or vice versa?

And we’re not limited to humanoids, either. If dragons decide to start domesticating stuff, what does that look like?

And, in fact, are the sapient species just what you end up with when the gods domesticate for their needs?

“Okay, we need something that breeds like a plague and has a predilection for idolatry.”

How deep does this rabbit hole go? And if fast-breeding populations are what the gods need, how nervous should the human kingdoms be about the new lapin-folk migrating from the Great Plains? Have you noticed that Artemis isn’t answering as many prayers as she used to?