I tamed a 135 using a net gun and dino gates. Netted it up near a wall, then placed 2 dino gates in a very acute triangle shape (almost totally parallel) to keep it from running around the redwoods while feeding… climbed right out of the top gap of the gates. I think it would work 3 or 4 gates closer together to keep it safer while feeding. Definitely recommend the net gun though. Was very easy to kill the non-alphas while the alpha was safely netted.
To take these you want to single out the one you want in the pack by killing any others around it and then it won’t fight back or run or attack so then build around it preferably spikes and it won’t hurt it’s self and you can take real quick
I found a couple in valguero scattered around various ponds (sorry I can’t really remember the names of the biomes or the areas. I can’t tell for sure if it’s a glitch or not but they didn’t spawn in large groups, 3 at max from what Ive seen.
Grapple to a tree, shoot all the baboons that don't have the red glow INCLUDING baby's. After they are dead, start shooting the alpha baboon until it's under 85% heath. You will know it's ready to tame when it just walks around. Put taming food of your choice in lost slot of your hot bar, then follow it around and tame.