[Kendall270]

What are the restrictions on the way that passive mobs can spawn? (something about no more than 5?)

And more to the point, how can i maximize mob production (sheep) in my realm without them de-spawning?

[jeniansmom]

was 5 or 6 in a 6x6x6 area the last time I knew, and that seems to hold true for my zombie grinder with a 2x2 opening, but even with that you have game glitches where mobs will suffocate if overcrowded (like I've heard the crunch of death and found random wool in the pen rather than the sheep despawning if that makes sense)

good luck!

[eah]

Jeniansmom has got it pretty straight. Here's a thread containing the statement from Intelli on mob de-spawning: http://minerealm.com/community/viewtopic.php?f=7&t=5551

You may also want to add thick walls between any pens because mobs can glitch through them. If the mobs of two pens are pressed against a single wall, some may de-spawn. So, I would recommend at least 3-block thick walls.