How about this: This is something I realise today. So I have 4 cats, 3 outdoor cats (have collars with bell) and 1 house cat (does not have a bell);

• one cat (A) guards the front door (because he can ask attention from anyone that went in/out),
• one cat (B) guards the back door (because there's a big box he likes to take a nap on),
• one cat (C) guards the balcony (because she dislikes company except from her owners, including the other cats),
• and lastly one cat (D) guards inside the house from the other cats (because he's the new, youngest and active, he will play with my other cats, but they don't like it since they're much older, so when the cats sneak inside this cat (D) will know and will chase them to "play" haha).

I started realising this because when Cat A sneak inside the house between my legs this morning, he made a U-turn when he saw Cat D waiting just behind a wall, watching her and ready to pounce 🤣 --