If you use the bear trap strategy which is if you lead it into a Dino gateway that is shaped in a triangle and with a bear trap in the middle (Large Beartrap) and when it is stuck you must put a dinogate behind it to trap it and then knock out. (hope this helped and "If" I win could it be an Xbox voucher, thanks.)
If you bring your high health Spino, hit the Rex once and it will just get distracted attacking your Spino instead of you. Just dismount and tranq it then when its running away just chase it as you tranq it then it shall get unconscious. My plan became successful. The rex i tamed was a.lvl 10.
Create a 3x3 mobile taming pen 3 walls high on a raft with a Dino gateway on one side and ramps on the other. Use a flyer to lead it up the ramp into the pen then move it to a safe area to tame. I got 2 150s without a single issue.
as u can see darts are the most effective. load up, have a friend pick u up in a bird, and fire away. i suggest the spike wall tactic just to be safe if you want a perfect tame! we got ourselves a 150 female earlier today and woke up at a lv 220!!
If you fly to where the beach touches the snow biome on the west coast of the island there's a huge rock you can tame them easily from. Nothing naturally attacks them when they're KO'd so you can just leave it there
I’m taming a lvl 5 right now and it took 22 tranq arrows (crossbow) to knock out and I’m using a mixture of raw fish, raw meat and raw prime to tame! I choose this way because I’m level 39 and not very good! (Please tell me if I’m doing good with the whole lvl 39 and a lvl 5 Rex)