In standard Minecraft, mobs that pick up items are marked with a flag, so they do not disappear. Usually, this is fine, but in some cases, it can lead to uncontrolled population, which causes image drops, player lag, and even server delays and excessive memory usage. Server operators have to manually remove these unwanted mobs.
One of the most common cases is when predator chickens wander around, equipping all zombies with eggs, but there are also a few others.
Mob population prevents marking mobs that collect unnecessary items in the configuration list as permanent. Instead, mobs will disappear as usual when players leave the area.


