How do Critter spawn locations work?

Hi all,

Was just wondering how the critter spawn locations work, and do they get deleted if a player builds something within a certain proximity?

I'm having a blast on my custom Omicron lately and, though I've not touched creature spawns, I'm having Spiders and the like appear close to my base often enough that my Sentry Turrets are proving most useful. This has been fun but, in the past, while I've sometimes (rarely) been attacked by a hostile creature during my initial base build,...

How do Critter spawn locations work?