Use boulders on a catapult and aim for the back of its shell, this is where you will get the most torpor
Don't hit it on the legs or shoot it with a cannon, it will not knock it out: hitting the legs does almost no torpor and a cannon will instantly kill it
Tranq Arrows/Darts DO NOT WORK!!! To knock this out you need to use a catapult and shoot in only on it's back. If you shoot it on it's legs it will kill it. UP-VOTE SO EVERYONE KNOWS & TO GET DODODEX TO ADD THIS!!!