A useful note: Animals fall into four categories:

1 – Creatures whose very nature is harmful: it is lawful to kill them and no expiation is required.

2 – Creatures that are neither edible nor harmful: killing them is disliked, and doing so within the Sacred Precinct or while in a state of ihram carries no expiation.

3 – Domesticated animals, such as livestock: their slaughter or sacrifice is permissible in every circumstance.

4 – Edible wild land animals—that is, game: killing any of these inside the Sanctuary or while in ihram incurs both liability for compensation and sin.