Just run into a forest until it gets stuck on some trees and the shoot it with tranqs easiest and best way

Go somewhere where the bronto can’t get you then shoot it with tranqs

Narcotic Making Machine...build a Chemistry bench on your bronto and carry spoiled meat on it. Go berry gathering and get all narco berries. Start crafting for thousands of narcotics!!

If u play on mobile get a load of mejos then go on a big roco and use tranqs on crossbow to knock out and tame

Simply find a sizable cliff and get it to chase you to it, then start pumping it full of Bill Cosby's special nectar