In my story there are those creatures that produce this substance. The substance can be used for many things, e.g. as fuel, or source of excellent illumination, etc. This is a pre industrial revolution society.
I'm basically remaking sperm oil. But instead of a whale I want it to be a land creature. Nothing that we consider fish or an animal capable of flying nor can it be a bug.
It should not be too small or too light. Roughly 2.5 meters and 250 kg minimum. Though we should no go crazy with the size as well. I'm just giving somewhat relevant biological limitations to help design the aspect I want.
I imagine it's easily controlled, tends to be in herds. However it has a long pregnancy period. 16-18 month. They are herbivores by the way
Most relevant part is the substance. That is what I need help with.
Basically what are the plausible and realistic explanations of a creature developing such a substance and in large quantities?
I left all other aspects up to you because it's irrelevant. If someone wants to have it be produced to cool it down or another says it helps it navigate it's all the same to me.
All I care about is a biological reason for a creature to produce such a substance. Like having a somewhat reasonable biological bases for that.