The Pegomastax is passively tamed by placing Mejoberries in the far-right hotbar slot and allowing it to repeatedly steal them, so keep it nearby and be prepared to continue the process. As a shoulder companion, it can pickpocket other players, gather seeds and berries while wandering, and reduce the weight of carried items. When encountering one, protect valuable items with a worthless bait item, since it can steal even while you ride; recover stolen goods by chasing it down, or knock it out if you intend to tame it.