No mythological creature is more varied than the dragon. From the compound-eyed, alien dragons of Anne McCaffery's Pern series to the chronically ill swamp dragons of Terry Pratchett's Discworld, dragons have been invented and reinvented countless times in popular fiction. It’s almost impossible to pin down traits that every fictional dragon shares with others—just look at the diversity of form that exists in the How To Train Your Dragon movies alone. But do any of these dragons have real-life counterparts in the animal kingdom? Dragons may not exist exactly as we know them from shows like Game of Thrones, but have any non-fictional creatures ever demonstrated distinctly draconic features?
To see how real-world creatures stack up next to fantasy's most beloved beast, I'm going to limit my analysis to three traits that most Western dragons share. Western dragons are most prevalent in North American fiction; when you shut your eyes and picture a dragon, the creature in your mind’s eye is probably huge, with wings and a propensity to breathe fire. I'll also be taking into account both extinct and extant non-fictional creatures to see whether dragons are, or at least were, real—in a way.
Big, Scaly Beasts
The dragons in fantasy are almost always depicted as reptiles, or at least reptilian, with scaly skin, horns, claws, and an egg-laying lifestyle. However, no living reptile reaches the gargantuan sizes that dragons typically do in fiction. Despite their draconic name, komodo dragons, the largest living lizard species, typically 'only' grow up to 150 pounds. The largest living reptile, the saltwater crocodile, can grow to a respectable length of 20 feet and a weight of 2,000 pounds—still no match for the immensity of The Hobbit's Smaug.
We have to look to the past to find creatures that really reach draconic proportions: the dinosaurs. Dinosaurs are one of the few non-fictional beasts truly comparable to dragons, because they grew so inconceivably large. The largest of the dinosaurs, the Titanosaurs, may have grown to lengths exceeding 130 feet, and weighed up to 90 metric tons. That’s longer than four school buses lined up end to end, and twelve times heavier than the heaviest living land animal, the elephant.
Of course, one couldn't just slap some wings on a titanosaur and call it a dragon. Animals that grow to massive sizes face important trade-offs. Mainly, the bigger you are, the more food you need. Not only that, but the bigger you are, the more energy it takes to move the sheer mass of yourself from place to place. Unlike speedy flying dragons, titanosaurs probably did not top three miles per hour walking all that bulk around. So even though animals of draconic size once existed, it's highly unlikely they even approached the speed of the dragons we know and love in fiction.
Things With Wings
In most dragon-centered fiction, dragons are able to fly. But in reality, flying is extraordinarily difficult, and the bigger an animal is, the more difficult flying becomes.
Take, for example, one of the largest animals ever to fly: the pterosaur Quetzalcoatlus. Standing as tall as a giraffe on all fours, this sky terror had a 35-foot wingspan, and could probably fly up to 80 miles an hour.
As with the Titanosaurs, however, there were important trade-offs to being so big. Like modern birds, Quetzalcoatlus had a lightweight beak instead of teeth, and utilized a system of air sacs within their bones and wing membranes. Most of the body was trimmed down for maximum aerodynamic efficiency, leaving Quetzalcoatlus looking less like a dragon and more like a giant, hairy stork with no tail.
Generally, dragons are depicted with fearsome teeth, long tails, and an assortment of bristling horns, which would all make them quite heavy in the air. To add even more weight, most fantasy dragons also have a third pair of limbs on their backs to serve as wings. It all adds up, and in reality, it would leave any creature—even with the best assortment of air sacs and hollow bones—struggling to get off the ground, let alone achieve true powered flight.
There aren't any animals today of draconic size that can fly, and few animals of that size that have ever been able to fly and look cool at the same time. (Sorry, Quetzalcoatlus–you looked something, but I’m not sure the word for it is ‘cool.’) So, if dragons as we know them from fiction were to suddenly become real, how would they get airborne? Here we may have to turn away from the world of biology and learn a little more about technology. The largest flying animal probably didn’t exceed 500 pounds, if that; however, one of the largest flying things, the Boeing 747, can weigh up to 485 tons. That’s five times as much as a Titanosaur! So how do such heavy planes manage to fly?
In theory, anything with the right wing shape can achieve lift: it just needs enough thrust to get up in the air, which can be hard to do as things get heavier. Planes achieve this with combustion engines, which provide enough force to lift the plane into the air. Now, I am not suggesting our hypothetical dragon could achieve flight by attaching engines to themselves (though that would be pretty awesome/terrifying). But the topic of combustion is a good segue into our next dragon-like animal.
Fire breath is likely the most magical aspect of the dragon, one that truly sets it apart as a fantastical creature: real animals may grow scaly and huge, and they may fly, but none are known to spit flames.
Considering the range of dangerous substances animals have evolved to harness—acid in our stomachs, venom in the fangs of snakes, cyanide in the tissue of a cassava plant—it’s almost surprising that none have ever used fire as a biological weapon. But there are animals who’ve evolved to use combustion for self-defense. The most famous is the bombardier beetle. These hot little bugs mix hydrogen peroxide and hydroquinone in special insulated chambers inside their abdomens. The chemical reaction releases so much heat that the liquid nearly reaches the boiling point, and a series of tiny explosions—yes, actual explosions—sends noxious, hot liquid spraying out of the beetle’s abdomen.
If a beetle can evolve chambers designed to contain explosions, it’s not too much of a stretch to reason that our imaginary dragon, perhaps utilizing the system of air sacs discussed before, might be able to store flammable liquid or gas in glands around their mouth, and combust them into fire for defense.
Combustion might also help our dragon get airborne. In series’ like Naomi Novik’s Temeraire, dragons have air sacs filled with lighter-than-air gas, allowing such behemoths to circumvent the weight issue by bobbing up like helium balloons. The ability to use chemical combustion could also theoretically heat the air inside and outside the dragon. Hot air balloons rise by the same principal, as heated air rises over cold air. Of course, the dragon would need to have specialized internal mechanisms to survive such heat!
Ultimately, dragons will only ever exist in the realm of fantasy, their abilities and prowess limited by our imaginations, not biological reality. But knowing a little about real animals who share some of their traits might help us gain better appreciation for the strange, diverse natural world around us...and will help the dragons in the media we enjoy start to feel that much more alive.
Featured still from "Game of Thrones" via HBO