OH HO!
Ok, removing the no eat/drink tags AND the likes site: dark fortress seems like an interesting avenue for testing.
172 year world, really varied elevation, all three major races can build roads/tunnels/bridges to encourage lots of activity and access, this is what happened:
Civilized World Population
13729 Dwarves
21942 Humans
4796 Elves
8648 Goblins
384 Kobolds
Total: 49499
A couple sample sites:
7: Ugarkutsmob, "Metmenaced", dark fortress
Owner: The Foolish Malice, goblins
Parent Civ: The Jackal of Growths, goblins
lord: Meng Whisperlances, dwarf
46 humans
44 dwarves
66 elves
1 three-eyed devil
2501 goblins
1350 trolls
1350 ogres
34 human prisoners
33 dwarf prisoners
3 elf prisoners
Still a lot, but not 10k like sometimes happens.
9: Roslastdostngosp, "Frenzycruelty", dark fortress
Owner: The Barbarity of Perfecting, goblins
Parent Civ: The Scorpion of Celebration, goblins
lord: Stasost Nightmareround the Bowel of Cradles, goblin
58 dwarves
16 elves
4 humans
51 goblins
1 three-eyed devil
350 trolls
27 dwarf prisoners
4 elf prisoners
Oh ho?
13: Olngomuk, "Monstrousmerchant", dark fortress
Owner: The Monster of Fragmenting, goblins
Parent Civ: The Lesser Savagery-Scourge, goblins
lord: Snodub Evillabor the Dour Thorns, goblin
75 dwarves
18 elves
178 goblins
1 bison brute
50 dwarf prisoners
3 elf prisoners
So it's not a fluke, had another world that had a couple forts like that, tried again and it still happens.
Found some more looking through the file:
121: Snustrokmato, "Soilswraiths", dark fortress
Owner: The Horror of Bugs, goblins
Parent Civ: The Lesser Savagery-Scourge, goblins
lady: Amxu Spiderspreads, goblin
729 goblins
158: Nakoxud, "Tormentslits", dark fortress
Owner: The Immorality of Memories, goblins
Parent Civ: The Scorpion of Celebration, goblins
lord: Utes Thiefdrools, goblin
1233 goblins
800 trolls
253: Ustuksos, "Nationsteal", dark fortress
Owner: The Horror of Rags, goblins
Parent Civ: The Scorpion of Celebration, goblins
lord: Snang Nightmarebrutal the Satiny Sparkle of Burns, goblin
822 goblins
500 trolls
281: Snudduosnun, "Pointghoul", dark fortress
Yes that last one is totally empty.
Several regular fortresses with gobs in em, usually under 100, and the usual smattering of them mixed around in dark pits and towns and such.
Oh my god, this world is freaking amazing... so I check the fort mode screen to see how the situation looks from there... I check with the first civ of the five available and find:
Nice! Wonder what the others have... nothing interesting, nothing interesting, nothing interesting, wait, what was that just now on the third civ?
Oh good lord, gob war with one civ, elf war with another, in the middle of three towers with highways everywhere and reasonable populations of gobs... did I mention that there should be like 20 megabeasts around?