In the Journal of an Unnamed Researcher:
The dragon, Dodongo, is a mysterious and dangerous animal that has lived as long as there has been history. It is a creature of living myth, and the last of the "dinosaurs." Once populous, the Dodongo are now nearing extinction. Thus, I have taken it upon myself to research these great beasts, and for the past year have lived out in a small cavern on Death Mountain with the permission of the Gorons.
Over the last year, I have made many surprising discoveries about the Dodongo, which I will write down here in sensible form, instead of letting the only records be my messy, scattered notes.
The first most important thing to note is that there are two different species of Dodongo: Two-legged and Four-legged.
The reason for the Two-legged Dodongo's lack of forelegs is something that is impossible to know at this late stage in their evolution. My best guess is that they lost the legs due to lack of predators, or a deformed gene that slowly led to the branching of a second species.
There are several key differences between the Two-legged and Four-legged Dodongo. To start with, the Four-legged Dodongo are known as the "King Dodongo." King Dodongo are much more powerful than Two-legged Dodongo, and live much longer. Their longevity allows them to grow to incredible sizes, as a Dodongo never stops growing throughout its entire lifetime. The largest known King Dodongo in history is the Giant Dead Dodongo in Dodongo's Cavern.
King Dodongo lay eggs about once every decade, and lay only half a dozen eggs at a time. King Dodongo are much fewer in number compared to their Two-legged counterparts, as they are more hardy and spend most of their young lives in the deepest caves where few outsiders can interrupt and kill them.
Two-legged Dodongo are simply known as Lesser Dodongo. The Lesser Dodongo are more populous than King Dodongo, but are considerably weaker. Lesser Dodongo live closer to the surface, and generally live in scattered groups. Since they are more susceptible to predators, they lay larger clutches of eggs: about ten eggs every two years.
Both species of Dodongo lay eggs in volcanic areas. After being fertilized, a female Dodongo will seek out a sandy pit where she can lay her eggs. Several females may all lay their clutches in one sand pit. Parent Dodongo do not watch over their eggs or care for their young. Baby Dodongo hatch as leg-less larva similar to tadpoles. The larva move around by wiggling their bodies and tails, much like snakes, and spend their entire infantile-form restricted to the sand pits.
No Dodongo is above eating a healthy, unarmored larva, and to avoid becoming a victim of an adult Dodongo's cannibalistic nature, larve spend almost all their time hidden below the sands. The larva use this skill to also hunt by listening to the vibrations in the ground. It waits for prey to come close to its hiding place, then uses its soft, but muscular tail to launch itself out of hiding, which is why Dodongo larva seem to "explode" out of the ground. With the prey caught by surprise, the larva will bite the prey, excreting the flammable oil that all Dodongo produce. This oil doubles as a venom that puts the prey into agonizing pain and renders them unable to move. Excreting this venom is a crucial tool in the larva learning to breathe fire.
Both species of Dodongo do not breathe fire so much as they "spit" fire. Dodongo produce natural flammable oil that travels throughout their bodies through a series of veins, not unlike blood. When feeling threatened, a Dodongo will open its mouth to a 120degree angle and squirt the liquid at the attackers. The fluid is then set aflame with a small spark pouch at the front of the mouth.
Despite their heavy armor of rock-hard scales, the Dodongo's weakness is its tail. Due to their cannibal tendencies, Dodongo have developed tails that break off from their bodies when caught by older, larger Dodongo. A Dodongo can survive and grow back another tail, however, due to the flammable liquid in its body, they can be set on fire while still bleeding. Like a line of gunpowder, the oil will carry a spark right back to the Dodongo's body and most often results in the animal exploding.
In rare events, a Dodongo's stomach, the most highly prized part of its body, will remain in one piece after it's exploding death. The Dodongo's stomach is very hardy and tough: the older the Dodongo, the better flame-resistant material it makes. Dodongo stomachs are primarily used for making bomb-bags, but are sometimes used in the making of very expensive, fireproof armor that are most often called "Goron Tunics." The oldest of Dodongo are even able to devour bomb-flowers with minimal negative side-effects, other than a severe bellyache. However, they are not completely immune, and if a large number of explosives are swallowed, there will no doubt be irreparable damage to the animal's stomach and it will die from internal bleeding.
Dodongo scales/hide are the second most-valued part of their bodies, which is always made into various pieces of armor, and a crucial material in making Goron Tunics.
Dodongo have no social hierarchy to speak of. They are primarily solitary creatures, and will bite one another at the slightest aggravation. They are also largely territorial, however they rarely roam a plot that is over a hundred square yards, save for the most enormous individuals. The Dodongo has little need for wide-open spaces, since they live in underground caverns. Typically, the only time another Dodongo will move into another one's territory is because of food and for mating.