They're fun to have around, they unlock doors. I dunno, don't ask me, maybe they have a monkey wrench xD. Anyways they are good to have on your shoulder on neutral as they throw poop at enemies when you are hit, which slows them down. Good for taming things like trikes, just keep whistling neutral, passive so they don't absolutely hammer the thing your trying to tame
While on your shoulder and on agressive it will throw shit at enemies that slows them down a lot and does some damage. Like the dilophosaur, this monkey has a turret mode where it will not move, but it will throw shit at enemies.
When taming wear gillie and drop them in a enclosed area to make taming easier when tamed they ride on your shoulder and throw poop at your target it slows the target and they can unlock wood thatch and stone doors but not metal when it's riding on your shoulder and your flying it will not fall over for any reason and if you spook it while trying to tame just leave its render for a few seconds and go back it will be unspooked
Tame a 135+ and you have a great companion. He/She can slow down attackers when on your shoulder by throwing poop at them (even alphas and brontos), collect berries when on wander and makes a surprisingly good guard dog in bases. I get mine to 1k health then pump melee. I usually get 400% minimum, that's 40 damage on a small, fast, pooping flinging creature. It'll rek wanna be intruders in your base, especially I'd you put a good helmet on it for armour.