Respawning bats in house

I made a big house and I closed all the doors, but I keep finding bats that respawn. I have seen sheep and chickens spawn, but the bats are 1) hard to kill because they move a lot and 2) always there, and it bothers me. I'm not sure why it's happening, but I keep killing the bats but they keep respawning. Thanks for reading my report, and I hope you can take the time to fix this.