Posts Tagged ‘dragon’

Building the Dragon II

Part II (Part I is here)

Continuing the question: will it breathe fire?

I threw out the idea of fire-breathing being a mating display, as there isn’t any biological need for a creature to breathe fire. Let’s put aside the question of why and look at how.


One commenter brought up hydrogen gas, which has the double advantage of being both flammable and lighter than air — it can be used to lighten your dragon for easier flying, whether by storing it on hollow bones or a gasbag (like a bullfrog’s throat pouch, or perhaps by going all the way to designing a zeppelin-like dragon).

However, hydrogen gas isn’t as common in nature as one might hope. Generating it by splitting water is simple — if you have electricity. Electricity-generating organs do exist in nature, of course, but most of them generate only mild fields. A small, specialized organ generating enough current to split water into component gasses could work, given a ready supply of water and enough metabolic energy to generate enough gas.

Hydrogen can be produced by some forms of algae (there has been some research on that in the bio-fuels field) but those require sunlight and the inside of a dragon is notoriously dark (or can you fix that?) Some sort of symbiotic microbe in the dragon’s gut, generating hydrogen from yesterday’s lunch, may be your best bet — your dragon gets his gas with minimal effort.

One more side note: no need for your dragon to eat rocks. Hydrogen is everywhere. It’s just a matter of separating it out.


Far less sexy than hydrogen, admittedly, but methane has the advantage of being easy to generate using existing microbes. It’s generated in the gut by bacteria which require neither light nor air, and could be accumulated in a specialized organ for siphoning back toward the head for ignition.

Or, you could be really brave and let the methane continue on its way to be expelled in the usual manner with a less-than-usual ignition organ under the tail… so that both ends of your dragon are equally dangerous… hey, it could still be a heck of a mating display.

And a non-flammable option


Hydrochloric acid, as produced in the stomachs of meat-eating animals, is quite able to burn exposed skin and eat through fabrics. More potent acids like sulfuric or nitric acid aren’t produced biologically but if one can invent a tough enough organ to store the stuff, I think it could be made quite plausible.

Unlike fire being a mating display, acid spraying makes more sense as a defensive mechanism along the lines of secreting surface poisons or explosive defecation. An acid-spraying dragon may well be short on the fangs and claws and other armaments, eat things that don’t need intensive hunting and killing, and be subject to predation by bigger, scarier monsters.

Which could be just as interesting as your standard-issue dragon, of course.

Building the Dragon

Part I (Part II is here)

Everybody loves dragons. And while wingless ones built along the lines of Komodo dragons or alligators can be a viable part of your fantasy ecosystem, let’s admit it. We want them up in the air and breathing fire or electricity or something fun.

A quick survey of existing flying creatures: the flying fox can get as large as 2.5 to 3 pounds and a wingspan of nearly four feet. The harpy eagle‘s wingspan can be 6 to 6.5 feet and they top out at 20 pounds or so.

Mind you, I would not want to meet a 20-pound dragon with a 6.5-foot wingspan, or be on the wrong side of its talons. And a hero would look really bad-ass when his pet swooped down to land on his (steel-reinforced) falconing glove.

Quetzalcoatlus scale comparison, by Matt Martyniuk (Dinoguy2), Mark Witton and Darren Naish, courtesy of Wikimedia Commons

In green, the Quetzalcoatlus northropi, with a human for comparison. Modified from a diagram featured in Witton and Naish (2008).

Let’s aim higher.

Quetzalcoatlus is the largest flying dinosaur discovered so far. Estimates vary, but it seems safe to assume a wingspan of 30 to 35 feet (9-10.5 m). Weight estimates have varied from as light as 150 to over a thousand pounds (68-453+ kg) (in a 2010 estimate generated mathematically). The first question is, of course, can this creature get into the air? Ostriches are the only current birds of similar weight — and they top out at 300 pounds.

Will it fly?

The issue was addressed by Witton and Habib in a 2010 paper on giant pterosaur flight dynamics. Their analysis of existing fossils and reconstructions of musculature led to some interesting possibilities. For their analysis, they settled on a Quetzalcoatlus of 32-36 foot (10-11 m) wingspan and 400-550 pound (180-250 kg) weight. Witton and Habib assert that these giant pterosaurs had sufficient bone strength and muscle for flying — with some mild caveats.

  • Assisted launching. The pterosaurs may have launched themselves with a strong jump followed by vigorous flapping. You can find a wide variety of birds using this strategy, especially larger ones like eagles. Others have suggested that pterosaurs may have used the running-start approach to launch or jumped off cliffs to get that initial burst of speed. Witton and Habib lean toward the jumping method, though.
  • Soaring. Rather than flapping constantly, pterosaurs may have done most of their flying by finding thermals and winds to soar on. Albatrosses and vultures do this a lot — it saves a great deal of energy, and when you’re big you need to save energy.
  • Moving on land. Pterosaurs were not built for it. But the authors theorize that they may have been able to get about by hopping/jumping (saltation, as sparrows do) and possibly bipedal walking (many birds do this — ducks, robins, hawks…).

What does it eat?

Witton and Naish wrote a 2008 paper on morphology, in which they addressed some of the questions of the morphology and ecology of giant pterosaurs, including Quetzalcoatlus. It’s good reference material, but chances are you aren’t building a dragon with a stork-like beak and a neck that’s long like a stork but less flexible — like a lizard. They lay out some reasonable options for such creatures, but a traditional dragon with a shorter muzzle, teeth, and greater neck flexibility will have more predatory options.

Bearing in mind the three rules of predators as formulated by me (and only me): 1. Don’t get hurt. 2. Don’t work too hard. 3. If it gets you food, do it. Also bear in mind that while an earth-bound predator can gorge on a kill and then slink away to digest, a flying predator can’t eat so much at once that he can’t fly away if threatened. Many small meals throughout the day are probably the best strategy.

  • Fishing. This is a perfectly good way to acquire a relatively large amount of calories with a reasonable amount of work. Given the general structure of a Quetzalcoatlus-based dragon, I would think that divebomb-style fishing (as done by ospreys and eagles) could work.
  • Carrion. It’s not glamorous, but it fulfills rules 2 and 3.
  • Traditional airborne hunting. This could be hunting birds, other dragons, or earth-bound prey, as falcons and hawks do. But bear in mind the stipulation about over-eating and the fact that it’s easier for a rabbit to hide in a forest than for a fish to hide in a lake. Hunting animals that congregate in large groups in meadows (or other open terrain) will make hunting easier… but also remember that we’re talking about a 30-foot wingspan dragon blotting out the sun. It’s difficult to miss that flying overhead, one would think. Or can you find a work-around for that?

Will it breathe fire?

Scientifically, the problem with breathing fire has always been the question why does it need to? Anne McCaffrey came up with one of the best answers (we bred them to do it) but in strict ecological terms, teeth and talons are quite sufficient for all your hunting needs. And if a feature isn’t useful to a creature’s survival, it isn’t done. Right?

Well, except for things that the opposite sex finds attractive. Such as peacock tails, silly dances, and the ability to compose sonnets.

Your mission, should you choose to accept it: imagine fire-breathing (or lightning bolts, what-have-you) as a mating display. We will get back to this in Part 2.