To tame: build a small trap out of stone pillars or metal pillars. Size it to fit a Therizino. Once it is in, block in its only exit and knock it out. I found that using berries was way less stressful than narcotics at mid level, because the Therizino would slowly gain torpor for a long amount of time instead of all at once for a few seconds. Using a Parasaur to collect the berries was very efficient. I had 400 extra narco berries. In the future I will use the same process for a higher level one.