Lyle was still.
He was using his ability to sense the blood of the monster, and for the last 10 minutes, whilst sensing the blood flow of the monster and that it was not the same as when a being was simply eating and resting, he didn't move.
He understood that the monster was still wary of its surroundings and had its guard up, the moment he moved would be the moment when the monster would drop what it was eating and would fight back.
It was a smart one. It dropped its tail and ears on purpose, purposely showing that it had let its guard down in order for whatever was nearby to show itself and attack it.
