Non-pets, such as mice and monkeys, can be freely killed with any IC reason such as pest control, or for food. These roles are often available in numbers as ghost roles, so removing one from the round doesn’t typically remove them all.
Pets, including but not limited to Ian, Renault, Remilia, and Hamlet, cannot be freely killed, they require escalation. These roles are often available once per round at most, with the exception of roles like Remilia.
Permanently trapping an animal, such as putting a mouse in a plant, is considered similar to killing the animal so should only be done with an IC reason.