[MC-1185] Some Mobs disappear after save&quit and reload or after unloading/loading the chunk they are in

I've seen this bug on my test level where I put Mobs in glass cages. (to let me see how the new textures are on them).

To reproduce it, make a glass cage 3 blocks high with only a space of 1 block in it:

Top view : 3x3 glass with a hole at the center
Side view : 3x4 glass with a hole of 3 blocks high at the center

Create the following Mobs with their Spawn Egg inside cage:

Witch : Can disappear
Ocelot : Can disappear
Blaze : Can disappear
Bats : Can disappear (and sometimes can pass through glass blocks)
Cave spider : Disappear
Villager : Can Can disappear
Silverfish : Can disappear
Enderman : Can disappear
Cow : Never disappear
Pig : Never disappear
Sheep : Never disappear

It happens when you walk far away and come back where the cages are.

Or, it can also happen after several quit/reload the level.

Linked issues

is duplicated by 2

MC-2900 Squids Escape Resolved

MC-10591 Not sure if this is a bug, but i put a pig on a bat with mcedit, and if you go far enough away, the bat had despawnd. Doesn't make much sense when it is attached to another mob. Resolved

Comments 6

kaleb bacon 2012-11-05T14:32:58Z

This happens because minecraft unloads chunks meaning all animals, mobs in them are despawned.

Jason Chmielewski 2012-11-29T00:20:09Z

More specifically, most hostile mobs are non-persistent (meaning they despawn,) and most passive and trained mobs are persistent (meaning they remain in-game.)

This is working as intended.

Sphax 2013-02-10T10:02:01Z

I don't know if it's a bug or WAD because I remember that Notch said ALL mobs will be persistent in the future... Currently, I understand only some of them are persistent...

Tails 2013-02-19T20:23:19Z

This works as intended an can be read up on the Minecraft Wiki.

Jamie Hart 2013-12-14T20:35:16Z

I put villagers in holding cells inside the village itself so they wouldn't wander around for trading purposes, this is the second time, all of them have disappeared. first time i thought they were too far outside the village boundaries, so i destroyed those holding cells and put them all inside the village boundaries. I went to the end, got killed. and when i got back to the village, all the holding cells were empty again. it took me awhile to get all those villagers in those cells, and have them as suitable trading partners, now they are gone. this needs to be fixed.

Ethan L! 2015-01-19T18:48:52Z

I'm getting this, too. I spawn some zombies, creepers, skeletons and villagers, all spawned with the PersistenceRequired:1 tag, and yet when I come back, half of them are gone. If this is intended, it should really be changed, as there is no reason this should happen at this point.