Originally posted by knighttemplar1960:

Anecdotally I have found that If I kill a troll outside a troll cave the cave contains no troll when I explore it.

I know at some point in the dev cycle I've seen troll pairs, one outside the cave guarding the entrance and one inside. Definitely stuck in my mind because I associated it with a mated pair, where the outside one was the male protecting a maternity nest for the female.

Like all these discussions of course the key words there are "at some point in the dev cycle", I have no recent memory of seeing this so perhaps current state a change in the spawn rules or a new bug has changed this.