I think this is a bug, when I played survival. It is useful a little bit because the animals are not moving, but it may need to be fixed.
Issue: Animals in jungle biomes (pig, chicken, cow, sheep) are glitched inside leaves, and the can't move from their spawnpoint.
Possible Solutions: Let the mobs go trough leaves (it will not be good if somebody live on the top of a tree and his animals are just falling of from his house)
Make the mobs do not spawn in jungle bioms. ( Not a good idea)
Make the mobs do not spawn on leaves. (Not a good idea)
Make the mobs spawn on the top of leaves. (If there is grass block underneath it) ( I think the best idea)