Build a wide wooden wall at least 3 storeys high and make a small door. Aggro the bronto and go through the door... It cannot climb something bigger then 3 walls on top of each other..... After trapping... Wish it Merry Christmas with tranqs.
Brontos are a bullet sponging machine if found with correct base health and melee you will make raiding easier can get 150 Brontos to around 70k health and swiping it's tail can destroy x seeds hella quick