Since writing my fanfiction involving my dragon form, I decided to make my own information about the biology and culture of dragons in MLP: Friendship is Magic. Many of it is hypothetical, but also based upon observing dragons in the show, and forming my own headcanons about how dragons behave.
Note: Although dragons, apart from a few such as Spike, are said to be scary and considerably dangerous in "Dragon Quest" I have observed there is more to dragons than when they were initially depicted in the show, as shown in "Gauntlet of Fire".
Dragons are one of the most recognizable and awe-inspiring creatures in the world of MLP. Most live beyond Equestria, though a few have been seen in Equestria (not counting the dragon migration). Well-known for their love of gems and fire-breathing abilities, dragons are essentially large reptiles with extraordinary abilities.
And as Twilight Sparkle once said, "ponies know next to nothing about dragons".
But observances in my dragon form has led me to discover more information about dragons. Here is the information I wrote down below. With some help from research on other reptiles.
As dragons are reptiles, it is easy to assume they are ectothermic, or cold-blooded. However, as they can breathe fire, it is more likely that they are actually endothermic, or warm-blooded. Since dragons often dwell in caves, as caves are ideal places for storing valuable treasure such as gems, this is more evidence that dragons are endothermic.
Nevertheless, dragons often like to lie in the sun when traveling, as sunlight can make a dragon feel "charged up" whenever they have flown for a long time.
Concerning dragons' fire-breathing abilities, it is a product of hot air. As we can produce hot air if we breathe slowly, rather than blowing, this applies to dragons' fire-breathing. Their bodies contain chemical gases that can come out through their saliva glands, and when they breathe hot air, the hot air ignites the chemical gases and allows them to emit fire from their mouths. Dragons' mouths are fire resistant.
Diet-wise, dragon's main diet are gems, crystals, and occasionally nuts and fruits. While most dragons primarily feed on gems and crystals, they are also capable of consuming plants and pony food, as demonstrated by Spike many times. They have been known to sometimes raid food from garbage disposal areas in Equestria.
As dragons' teeth are mostly sharp, this is effective for smashing gems and grinding them into a powder worth consuming. Gems and crystals are a good source of vitamins and minerals for dragons, and darker colored gems and crystals are especially good for younger dragons.
For a long time, what ponies knew about dragon culture was that dragons could be considerably fierce, competitive, and rather aloof. There is more to dragon culture than this. Dragons are often loners, but they will gather together during migrations, courting, and when there is enough food and valuable treasures for all. Although many wild adult dragons don't like to share their treasures, when there is more than enough in one area, they will share. Dragons who know each other well will also share gems and treasures together, especially if there is a benefit for all of them.
It is not uncommon for dragons who are siblings to share food and treasure together, especially if they love each other and get along well. This happens with dragons who are mates too, or a couple as ponies would call them.This shows that dragons do have family bonds much like ponies.
When courting, dragons like to bring gems or other valuable objects to potential mates, as well as say words about what they find most impressive, lovable, and attractive about them. A few dragons have even recited their own form of poetry to their potential mates.
Dragon society is governed by the Dragon Lord, the top authority leader of all dragons. Their authority is mostly based on summoning dragons for an important event, such as warning them of a natural disaster about to happen (such as an earthquake), issuing a new rule, or participating in diplomatic relations with other sentient creatures. And also informing dragons of which dragon could become the new Dragon Lord in the Gauntlet of Fire competition.
The title of Dragon Lord also allows the Lord to appoint other dragons as his or her advisers, or scouts. Dragon scouts are useful since their tracking skills allow them to bring in important information to the Lord. Although dragon government is not as complex as that of other kingdoms, such as ponies or the hippogriffs, dragons nevertheless have a sense of order that concentrates mainly around the Lord's land.
According to Spike's experiences in the Dragon Lands, unlike royalty among ponies, the title of Dragon Lord does not last until the Lord's death. Dragon custom dictates that the Dragon Lord steps down after a considerable amount of time.
It is not clear exactly how long a dragon can be Dragon Lord. But based on former Lord Torch's speech, I would consider that it could be a length of 10 years or more, depending on how successful the Lord is in his or her reign. I believe Torch may have been Lord for at least several decades, given on how he said how "supreme" his reign was. In other words, there is no strict limit on the Lord's reign, but a reign for 50 years I would consider to be the longest allowed.
Since Ember is the current Dragon Lord, much is now known on what the Lord can do in diplomatic relations. A Dragon Lord can either send an ambassador to the kingdom in question, or come to the kingdom themselves, for the purpose of establishing stronger ties and understanding. Resources from the other kingdom can also offer benefits for dragon society too.
A common negative stereotype of dragons, at least before the stronger diplomatic ties with ponies with Ember as Lord, is, or was, that they are overly competitive, hostile towards other sentient species, and overall greedy and mean.
But that is far from the overall nature of dragons. Although it is a natural tendency of a dragon to collect valuable objects, not all dragons are greedy. As mentioned above, many dragons will share food and valuable treasure with other dragons that they are close to. Some dragons aren't even interested in treasure.
The relations between dragons and ponies, and indeed, other sentient creatures, has historically been rather rocky. But over time, dragons have come to appreciate friendship more, and relations between dragons and ponies have become stronger and greater. The stereotype that dragons don't like what ponies do, such as hugs and exchanging gifts, isn't entirely unfounded. But a number of dragons I have interviewed admit that they actually enjoy hugs and gifts and don't really mind "pony ways". Some dragons are even fascinated with ponies, showing an eager desire to learn more about them.
Dragons have also held stronger ties with other creature kingdoms such as griffons, hippogriffs, and yaks, since Ember become Lord. The importance of friendship has been recognized by Ember, and thus at least one young dragon has been sent to the School of Friendship in Equestria, by the name of Smolder.
As dragons have become better known, it is clear that they are somewhat complex creatures, with an inclination towards collecting valuable objects. But although they can be fierce and often competitive, most dragons have a sense of common morality and thus it is disapproved in dragon society to steal from other creatures. One particular dragon, named Garble, that I learned about, was a real jerk. He didn't represent the positive qualities of dragons.
Overall, dragons have a strong sense of honor and respectability, and while they can be rather aloof sometimes, it is possible to have a dragon as a friend. Most dragons that I have met are fiercely loyal to friends and embody the good principles of having a sense of good self-worth. Dragons make useful allies when battling evil individuals, and a good dragon will never betray or abandon you.
That is all the information I have, whether from observances in the TV show, or based on my headcanon, about dragons in the land of MLP.
Hope you liked this information, and remember, dragons in MLP are individuals like ponies are. No two dragons are exactly alike.