Originally posted by Horemvore:

Originally posted by knighttemplar1960:

Grass/no grass makes no difference (especially in the biomes that lack grass)..

Spawning logic:
https://valheim.fandom.com/wiki/Spawn_zones
Base items that prevent spawning.
https://valheim.fandom.com/wiki/Player_base

Just a note it may be a bug or it may be intentional but deer and birds can spawn in even if your base has complete anti-spawn coverage.
https://steamcommunity.com/sharedfiles/filedetails/?id=2920176358
https://steamcommunity.com/sharedfiles/filedetails/?id=2860289081

Cause they are passive Animals, not monsters.

Except that it works to prevent them from spawning "most" of the time. I have over 1,000 game days in each of those worlds with each of those bases and the deer spawn inside only on very rare occasions. There are spawn points for deer outside the radius of both those bases and they spawn every 3 game days.