Despawning problem in Minecraft

Why do my animals keep despawning?
I went to chop down some trees and organise my storage system. When I returned to see my animals, they were mostly gone. I don't know about Villagers if this was the same or if a Zombie horde attacked them. It may be my low-end tablet (I'm on Pocket Edition). My render distance is 4 chunks.


Most mobs will despawn unless any of the following are true:

  • Cannot Move 20 blocks in any direction
  • Are named with a name tag
  • Are saddled/tamed
  • Are on a lead connected to a fence
  • Are a special mob (i.e. Iron Golem, Wither, etc.)