I’ve had several unpleasant experiences with the wildlife entering the arena. While I am fine with the monster choosing strategic fights around dangerous wildlife, there is no fun in a dune beetle suddenly running into the arena cause he chased you from across the map. Or a tyrant suddenly entering it, not being able to exit the arena and going absolutely mental on any hunter that comes close.
Please, the wildlife already helps the monster more than enough. This can lead to some really frustrating experiences, without it being a mistake from the hunters or something skilful done by the monsters.