One of the coolest ways to say ‘You’re not in Kansas anymore’ is to have flying mounts in your world. Or if not a flying mount, some bad-ass horse-alternative like a giant flightless bird, or giant canine, or even a giant feline; in short, badass often means carnivore.
Done carelessly though, this can shoot a conworld’s believability full of holes. Let’s leave the questions of gravity and aeronautics aside for now, but focus instead on the factor that has the greatest impact on the rest of the setting; fuel. What does your big, badass, carnivorous, maybe flying mount eat? How much, and how often? And where do you get it?
An animal large and strong enough to carry a human in flight is certain to require lots of food. If it’s a carnivore, it needs a lot of meat; if a herbivore, it needs a lot of fodder, an even greater mass of it since plant matter contains a lower calorie concentration than meat. There’s also the issue of a herbivorous digestion requiring a larger stomach or constant feeding, or both. It’s why a cow spends more time eating than a tiger does.
Carnivorousness creates another problem: territoriality. Eagles, which weigh far less than a dog and would have difficulty carrying even a small child any distance, require huge hunting ranges just to feed themselves. This makes them highly territorial, and thus, rather antisocial among their own kind. How can we then keep giant eagles or the like in a stable?
In Anne McCaffrey’s Dragonriders of Pern series, the pastoral economy of Pern revolves around providing the dragon-weyrs with a tribute of livestock. The dragonriders are few, but their mounts consume a large proportion of their world’s food production. The weyrs’ requirements are so high, that in Dragonriders of Pern one of the lord holders threatens to rebel against the system.
In James Cameron’s Avatar, the Na’Vi tame giant raptors for hunting. Their entire planet is a jungle, and the Na’Vi are few, so as long as they keep their planet a jungle, there will be enough meat to go around. Avatar also offers a solution to the eagles-in-a-stable conundrum: the mountain banshees nest in rookeries like seabirds. They’re already social by nature, despite their carnivorousness.
In S.M. Stirling’s In the Courts of the Crimson Kings, a few elite Martians keep stables of genetically engineered giant eagles, Paiteng. At first I found this really odd by the lights of the setting – how do you get enough feed on a dying planet? But then you remember that the Martians are master biotechnologists, and their main source of meat is renewable; their domesticated, or rather genetically engineered Rooz bird grows a neck-flap of meat that regrows after harvesting. The Paiteng are very few, reserved only for the elites. As for their territoriality, again they’ve likely been genetically engineered to be social.
Jared Diamond’s book Guns, Germs and Steel offers a very valuable insight for world-builders in the section where he compares animal domestication patterns worldwide. Why, of all the animals large enough to carry a human being, did the horse end up our main carrier by such a huge margin? Diamond cites a host of factors that all came together in the horse that were lacking in other ungulates, even in its close relatives the zebra and the wild ass.
The horse had just the right mix of anatomical build, sociability and disposition, genetics (which allowed the development of different breeds for different purposes), dietary requirements, hardiness and adaptability to suit our needs. Zebras, donkeys, antelope, the South American camelids, buffaloes and oxen did not. Charles Saunders’ vision of African tribal cavalry on Cape Buffalos kicks ass, but it’s very unlikely; the Cape Buffalo is simply too badass to be tamed that way.
Finding the right balance between Rule of Cool and plausibility is always a challenge. I’m currently mulling over a new sword-and-planet novel, and yes, I want flying mounts in it; but coming up with a believable premise that hasn’t been done before is not easy.
Giant, social flying piscivores won’t work because the setting is a desert planet. The genetic engineering/advanced biotech angle doesn’t work for me either, because the setting is post-apocalyptic. That environmental premise also knocks out the Avatar-style notion that there’s simply enough to be hunted.
I think I have my idea down for the terrestrial riding animal though: A fleet desert-dweller, warm-blooded dinosauroid, lives in small herds, scratches insects and roots from the desert floor with its big foreclaws rather like a meerkat. Rears up into bipedal stance to fight with those same claws, thus battle mounts are fitted with thoracic armor.
Since I’ve a fascination with Asian history and war elephants, I couldn’t resist coming up with a giant-size war beast: A big ape-like creature, normally walks on four limbs but switches to bipedal mode to fight. Its hands are often armored in steel, because its favorite attack is to smash down with doubled fists, a la the Hulk. In sieges, it throws big stones and tears gates from their hinges. A living tank, catapult, and wrecking machine all in one … and yes, it’s a herbivore because otherwise it’d be too much to feed.
PS. I started writing meaning to say something about Tolkien’s wargs and He-Man’s Battle Cat, but I guess I said all I needed to about predators as riding animals already.