I have been attempting to make a race of cave goblins, similar in many ways, but significantly less civilized, than regular goblins (and they also need food and drink, among other differences). As such, they appropriately live in caves.
However, the issue I have found, is that when a civilization's default site is caves, they do not expand. At all. Not even if they "like" other sites instead of merely tolerating them. I suppose they may inhabit little ruins, like how kobolds sometimes will take residence in necromancer towers, but they do not live in larger scale ruins like cities, so far as I can tell. Of course, they do not even expand to other caves, as was my intent to begin with. The [SKULKING] tag appears to have nothing to do with it, I have tested it.
Strangely, when caves are made to be one of their "liked" sites, and their default site is set to something else (like CAVE_DETAILED), they will begin to inhabit caves as one would expect.
No changes I have been able to think of seem to change this at all. Not changes to food sources (like adding the ability to farm or take care of animals), or combinations of liked and tolerated sites, though I have not tried them all.
I recall at one point trying to mod vanilla goblins to be able to inhabit only caves somehow, and somehow that seemed to work just fine. But I'm not sure if it was as I remember, or how I went about it if it did actually work that way.
Strange detail I noticed about Kobolds is that their default site is of course caves, but they also both like and tolerate caves. Though this is the case, they never expand to other caves, though they are said to hang out in outdoor camps, and in some ruins like I mentioned before, though they don't inhabit larger, populous sites.
Might anyone have any ideas on this? I am at quite a loss, at this point. It appears to be a complete, unassailable wall, which cannot be passed by any means.
Is there any way to limit sites construction for a civilization, so though the civilization will start in one type of site, they won't build any more, but still inhabit conquered/abandoned sites, as well as caves? Is there any kind of work-around?