To knockout or kill the Doedicurus shoot him in the head and walk Backwaren White reloading and continue to shoot it in the head. If you do so it wont be able to Hit you. If it flees slowly follow it and am for it legt or tall.
Not sure where this goes but if u place a spike wall in front of them and when their health is low enough they have to turn into a ball and be stuck in a constant cycle until the spike wall is removed. It's a great way if you find one and want to tame it later. Unless it gets killed by something else while in a ball it should be fine. I stil have one stuck on one of my walls and ima keep it ther until I can tame it for stones.