I spent about 56 tranq darts and around 100 tranq arrows to knock out a level 140. Mainly because a lot of the darts and arrows were not registered as hits. I found the best place to aim at was the head I wouldn't waste my darts trying to hit the tail from above as they rarely registered. I had it trapped in a pit style trap so I was above it shooting down.
Tranq arrows are fine, shoot in the face, walk backwards and continue shooting in the face, if you can shoot the underside when he turns, then go ahead. It is a little difficult to time that however. When it starts to run away from you, just keep in front of it and keep shooting it in the face. If for any reason it rolls up into a ball, let it go and find another one. If you are intent on taming it, put a structure around it to keep it safe, then sit by it for about 45 minutes to an hour, it will heal faster if you are within render of it. Leveling up the melee allows it to collect more rock with each swipe of the tail. If you are so low, put most of it in weight and some in melee, this will allow you to collect more with less trips. If you have a tribemate, and you are using a Quetzal or a skiff, then only level melee.