For some reason... I think Aikar changed it again. So that they don't despawn (when bats were changed)
Don't bats disappear after a while though? All Brit's did and I just spawned a squid in her aquarium. Guess I'll check it later to see if it stays.
bats are not supposed to spawn. but they weren't designed to not despawn so sometimes they glitch through walls and perhaps suffocate