Return to Answer

Another school of thought is that young dragons fly in order to disperse themselves from their parents (since a carnivore weighing several tons would eat a whole lot), and lose their ability to fly as they grow. An adult dragon may retain wings, but use them for display, not flight.

1. Some organisms (known as extremophiles) are known to live and grow in temperatures below freezing and above boiling point, achieving this through specialized proteins. Some desert living mammals (whose normal body temperature is 37°C) can survive a body temperature up to 50°C, whereas huamns start having problems with hyperthermia at 42°C or less. It is not beyond the bounds of possibility that a dragon could have evolved proteins that allow it to survive much higher than normal body temperatures, perhaps well beyond 50°C, though most likely not over boiling point.

2. Where parts of animals bodies experience extremes of temperature, counter-current heat exchange mechanisms in their blood vessels greatly reduces the flow of heat to or from the extremities exposed to those temperatures. By selectively passing blood through countercurrent heat exchangers or not, peripherals can be maintained at a higher or lower temperature than the body core.

3. Carbon (which is in relatively abundant supply in carbon-based organisms) in the form of nanotubes or sheets has very high thermal conductivity. By strategically placement of such materials, the heating effect of point heat sources could be spread over a wider area and even transmitted rapidly deeper into the body, preventing burns by allowing an overall but lower increase in body temperature. Such materials also have the added bonus of being very strong. It is not beyond the bounds of possibility that a dragon may have evolved to be able to produce such substances.

4. By maintaining a high body mass, an organism which uses water as a solute for its metabolism would require a great amount of heat to raise its body temperature significantly - water has amongst the highest heat capacities of any substance per unit mass.

5. Creatures whose body temperatures rise higher than normal must eliminate heat, by radiation and/or evaporation. Having a large pair of wings gives a dragon a large surface area through which it can radiate and evaporate excess heat, and its large mass gives it plenty of water that it can evaporate to shed the large amounts of heat that may be involved.

Another school of thought is that young dragons fly in order to disperse themselves from their parents, since a carnivore weighing several tons would eat a whole lot, and lose their ability to fly as they grow. An adult dragon may retain wings, but use them for display, not flight.

1. Some organisms, known as extremophiles, are known to live and grow in temperatures below freezing and above boiling point, achieving this through specialized proteins. Some desert living mammals, whose normal body temperature is 37°C, can survive a body temperature up to 50°C, whereas humans start having problems with hyperthermia at 42°C or less. It is not beyond the bounds of possibility that a dragon could have evolved proteins that allow it to survive much higher than normal body temperatures, perhaps well beyond 50°C, though most likely not over boiling point.

2. Where parts of animals bodies experience extremes of temperature, counter-current heat exchange mechanisms in their blood vessels greatly reduces the flow of heat to or from the extremities exposed to those temperatures. By selectively passing blood through countercurrent heat exchangers or not, peripherals can be maintained at a higher or lower temperature than the body core.

3. Carbon (which is in relatively abundant supply in carbon-based organisms) in the form of nanotubes or sheets has very high thermal conductivity. By strategic placement of such materials, the heating effect of point heat sources could be spread over a wider area and even transmitted rapidly deeper into the body, preventing burns by allowing an overall, but lower, increase in body temperature. Such materials also have the added bonus of being very strong. It is not beyond the bounds of possibility that a dragon may have evolved to be able to produce such substances.

4. By maintaining a high body mass, an organism which uses water as a solute for its metabolism would require a great amount of heat to raise its body temperature significantly - water has amongst the highest heat capacities of any substance per unit mass.

5. Creatures whose body temperatures rise higher than normal must eliminate heat, by radiation and/or evaporation. Having a large pair of wings gives a dragon a large surface area through which it can radiate and evaporate excess heat, and its large mass gives it plenty of water that it can evaporate to shed the large amounts of heat that may be involved.

Carnivorous

Fireproof

The point of "breathing" fire in the manner I have suggested means that for the most part, a dragon need not actually be too fireproof, since like a human fire-eater, the fire is not inside the dragon. On the other hand, a certain degree of heat resistance would be useful for a creature that could make a mistake with its own fire - or get into a fight with another creature that also produces fire.

There are a number of adaptations that could help a creature that must maintain a relatively low body temperature deal with extremes of heat.

1. Some organisms (known as extremophiles) are known to live and grow in temperatures below freezing and above boiling point, achieving this through specialized proteins. Some desert living mammals (whose normal body temperature is 37°C) can survive a body temperature up to 50°C, whereas huamns start having problems with hyperthermia at 42°C or less. It is not beyond the bounds of possibility that a dragon could have evolved proteins that allow it to survive much higher than normal body temperatures, perhaps well beyond 50°C, though most likely not over boiling point.

2. Where parts of animals bodies experience extremes of temperature, counter-current heat exchange mechanisms in their blood vessels greatly reduces the flow of heat to or from the extremities exposed to those temperatures. By selectively passing blood through countercurrent heat exchangers or not, peripherals can be maintained at a higher or lower temperature than the body core.

3. Carbon (which is in relatively abundant supply in carbon-based organisms) in the form of nanotubes or sheets has very high thermal conductivity. By strategically placement of such materials, the heating effect of point heat sources could be spread over a wider area and even transmitted rapidly deeper into the body, preventing burns by allowing an overall but lower increase in body temperature. Such materials also have the added bonus of being very strong. It is not beyond the bounds of possibility that a dragon may have evolved to be able to produce such substances.

4. By maintaining a high body mass, an organism which uses water as a solute for its metabolism would require a great amount of heat to raise its body temperature significantly - water has amongst the highest heat capacities of any substance per unit mass.

5. Creatures whose body temperatures rise higher than normal must eliminate heat, by radiation and/or evaporation. Having a large pair of wings gives a dragon a large surface area through which it can radiate and evaporate excess heat, and its large mass gives it plenty of water that it can evaporate to shed the large amounts of heat that may be involved.

The combination of all these factors may result in a creature that, at its adult size, could be trapped in a burning wooden building for quite some time before it was particularly inconvenienced by excess heat, possibly on the order of some minutes to a quarter hour or so before its body temperature rose to a point that threatened its life. If it escaped such a situation alive, it could then shed the excess heat quite quickly.

Carnivorous

The main argument against mountain-sized dragons is the square/cube law. As an animal increases in size in its linear dimensions, but retains roughly the same proportions, its surface area and strength increases proportional to the square of its length, but its mass increases proportional to the cube of its length.

As the question specifies, using earth-like biology and conditions, the upper limit of size for a land animal would be on the order of tens of tons, certainly not more than a hundred tons.

Another school of thought is that young dragons fly in order to disperse themselves from their parents (since a carnivore weighing several tons would eat a whole lot), and lose their ability to fly as they grow. An adult dragon may retain wings, but use them for display, not flight.

The main problem with fire-breathing is the amount of energy required to produce the reactants. Whether the dragon itself or some symbiotic organism produces the reactant, it takes an input of at least as much energy to produce the fuel as the release of energy when the fuel combusts. The best solution is if the energy comes from outside, as is the case with Anne McCafferey's Pernese dragons.

Growth / size

The main argument against mountain-sized dragons is the square/cube law. As an animal increases in size in its linear dimensions, but retains roughly the same proportions, its surface area and strength increases proportional to the square of its length, but its mass increases proportional to the cube of its length.

As the question specifies, using earth-like biology and conditions, the upper limit of size for a land animal would be on the order of tens of tons, certainly not more than a hundred tons.

Flight

Another school of thought is that young dragons fly in order to disperse themselves from their parents (since a carnivore weighing several tons would eat a whole lot), and lose their ability to fly as they grow. An adult dragon may retain wings, but use them for display, not flight.

Breathing fire

The main problem with fire-breathing is the amount of energy required to produce the reactants. Whether the dragon itself or some symbiotic organism produces the reactant, it takes an input of at least as much energy to produce the fuel as the release of energy when the fuel combusts. The best solution is if the energy comes from outside, as is the case with Anne McCafferey's Pernese dragons.

Carnivorous