While a link between dragons and fire is obvious, I would go further that volcanic environmental conditions are dragons preferred habitat, and possibly necessary for dragons to lay clutches of eggs.
Much has been known and discussed of the specific environmental conditions dragon eggs require to hatch. Targaryen attempts to induce hatching ranged from placing them in their children’s cradles to the horrors of Summerhall, and through Dany we witness eggs hatching within a fiery pyre. However, there has been almost nothing on the possible conditional requirements for dragons to lay eggs.
Below is an analysis which I conclude that dragons are very sensitive to their environments, possibly requiring volcanic habitat to survive as a species. Reviewing WOIAF I was able to identify only four locations of established volcanic activity. I also review the other locations that potentially have volcanic activity and non-volcanic locations where dragons reside.
Identified Volcanic Locations
The fourteen volcanoes of the freehold was a highly active volcanic region. Volcanic activity seems to be continuing with a smoking sea. Post doom Valyria appears to be extremely dangerous, even to dragons, for exact reasons unknown as no visitors have returned to explain why. Unless you believe Eron Greyjoy.
Valyria was a natural habitat of dragons among fourteen active volcanoes. According to Valyrian legends dragons seemed to thrive in the wilds of Valyria, and once tamed and ridden by the Valyrians as a tool of war they helped them thrive as a conquering slaving empire. At the height of Valyrian influence they controlled the majority of central and western Essos. However, the forty dragonlord families and their dragons resided almost exclusively in the city of Valyria, close to volcanoes. The sole exception was the Targaryen family, who was ridiculed by dragonlord society after moving away from Valyria based on the accurate prophetic dreams by Daenys the Dreamer of the impending Doom. With all of their extensive belongings, including five dragons, the Targaryen’s traveled to the very edge of the Valyrian Empire. Dragonstone, a castle on the side of an active volcano.
After the Doom, stories emerged that only three non Targaryian Valyrian dragonlords and their dragons had survived in Essos by not being in Valyria during the event;Tyrosh, Lys and Qohor. In the cases of Tyrosh and Lys the dragonlords/dragons had been killed by uprisings, while in Qohor the dragonlord raised an army, and with a dragon marched to Valyria, and were never heard from again. This would indicate that their were no dragonlords living in Volantis, which seems odd considering its size and importance.
Accounts from the Rhoynar had Valyrian dragon population at over three hundred, putting the Valyrian Doom survival rate at 1%. An empire spread over a continent, and only a tiny fraction had lived elsewhere outside of Valyria proper.
Dragonlords always stayed close to home, and home always had volcanos.
Located in Blackwater Bay the castle of Dragonstone had been the home of the Targaryen family since before the Doom. The evidence that dragons thrived on Dragonmont is strong, giving me no doubt that the volcanic island is a preferred dragon habitat.
When wild and tame unpaired dragons “dwelled”, it was in a volcanic environment.
The fact that hatcheries existed on Dragonstone speaks to the fertility of dragons residing there. I think it is clear that Dragonmont’s active volcano was prefered by dragons as a habitat, with an emphasis of proven fertility.
Clusters of hot springs are a form of passive, but sustained volcanic activity. There are also Winterfell connections to dragons.
Admittedly this reference is a weak connection, but it does reinforce the volcanic nature of the Winterfell hot springs and introduce dragons within the local folklore.
I trust Mushroom, his attention to detail makes me feel that he is writing from memory, not elaborate fiction and his accounts had been validated by a second source.
Does Winterfell have an untold history with dragons? Possibly, but the evidence of volcanic activity is clear.
Located in the Jade Sea is Marahai, this is the only reference and is clearly volcanic. It would be logically to conclude that this would be a good dragon habitat.
There have been theories that Hardhome was a volcanic explosion. A landscape of charred trees, burned bones is not volcanic, that’s dragons. Volcanic events do not leave “waters choked with swollen corpses”, an erupting volcanoes burns everything it touches and more than likely creates a new layer of rock on top of whatever was there before. Volcanic events are all about impossibly hot temperatures, and doesn't compute with accounts of bloated bodies.
Also, references to sounds coming from cave mouths closely parallel to the Whipsers on Crackclaw Point, which is a natural cave effect.
Valyrians had been on Dragonstone 200 years before the Doom of Valyria, the Doom having occurred in 114 BC. This places the arrival of the Valyrians in Blackwater Bay at roughly 314 BC, 614 years before the events of the books.
The Hardhome incident was 600 years before the events of the books, right when the Valyrians were establishing themselves in the Narrow Sea region. I would imagine they would have done some slave harvesting, being in their nature. In my opinion the descriptions of Hardhome resembles a slave operation, with dragon support. If a number of dragons had been burning hell onto the Wildlings, igniting the surrounding forest, then it would have been observable from the Wall.
Mother of Mountains
Lonely peaks tend to be volcanic in origin. Considering the possibility of Dany uniting the Dotharaki kalasars on the back of a dragon within view of the Mother of Mountains, something could happen...maybe.
While there is no direct mention of volcanic activity in and around Asshai, there is a river that is toxic, black, and named Ash. For all the dark mysteries surrounding this region, discovering that it has volcanic activity would be unsurprising.
There is also some evidence that the Shadow near Asshai is the source of all dragons, contrary to the Valyrian origin story.
Asshai is also known to be a source of ancient dragon eggs.
Yandal also writes about dragons in the cliffs leading into the Shadow, but then immediately discounts them as fairy tales.
There are many references to the laying of eggs at Dragonstone, it even had a hatchery built in fused black stone. In contrast there are no references to dragons having laid eggs at either the King's Landing or Meereen dragon pits. As for Drogon, Viserion and Rhaegal, they are possibly too young still to lay eggs, meaning the absence of them laying eggs holds less weight. However, the suppressed growth of dragons enclosed in pits does demonstrate how susceptible dragons are to their environment. It’s clear that the dragon pits are not an ideal habitat for dragons to thrive and procreate.
Throughout the books are a number of references to brimstone or sulfur smelling water. While sulfurous waters do occur around volcanic regions, they are not exclusive to them. In many cases it is caused by sulfate reducing bacteria. I disregard these accounts as volcanic regions unless accompanied by other indicators, primarily heat.
Dragons and Gender
The accounts of Mushroom, that “Vermax left a clutch of eggs somewhere in the depths of Winterfell’s crypts, where the waters of the host springs run close to the walls.” was dismissed. Aside from Yandals bias against Mushroom, this disregard was justified due to the orthodox belief that dragons have gender, which seems to be only identifiable by observing which dragons laid eggs. A vigorous scholarly debate exists among Maesters on the subject of dragon gender and mating, indicating that the sexual process was not obvious?!?
Dragon sexualtiy was also a much researched topic by Egg, though his obsession was on the hatching problem. Fertility of dragons is a mute point with no dragons.
Perhaps a young maester Marwyn had been sent by Aegon to Asshai? Summerhall was destroyed in 259 AC, making it possible.
While Ageon V and recent maesters would have been disadvantaged by not having a live dragon to observe, Septon Barth’s opportunity to observe dragons would have been limitless, being Hand during the reign of Jaehareys l, the high point of Westerosi dragon population.
Having such multiple divergent views on a matter that could be reasonably explained by observing dragon sex, leads me to believe that no maester have seen dragons mating.
I believe that Maester Aemon was correct in reinterpreting Septon Barth’s work that dragons are genderless, or could change their genders. I am not confident in Aemon’s prophecy interpretations, as I share Maester Maryns views on the pursuit.
There are real life examples of lizards changing genders, like the Central Bearded Dragon of Australia, where stress from climate change is resulting in male lizards procreating. Creatures which evolve to be genderless, or the capacity to shift genders, would be enhanced in their chances for successful procreation. Need for such flexibility in procreation would make sense if dragons could only lay clutches of eggs in volcanic environments.
I propose that dragons prefer, if not require, volcanic regions to lay eggs and procreate. They are also gender-less or sex changers to take advantage of the opportunity to procreate due to the relatively rarity of volcanic environments. Even if volcanic conditions are not necessary for laying eggs, there is enough evidence in the comparisons between Dragonstone and the dragonpit to conclude that dragons prefer volcanic habitats.
A review of the World of Ice and Fire find only a few established volcanic locations, some of which are documented as having dragons been ruled by dragonlords, and/or have been referenced as locations dragons have laid eggs. It would only make sense that any empire with dragonlords would have been keenly interested in all volcanic regions, as they would be the only locations dragons could grow and thrive.