They seem to like a bit of abuse. If the Pego is standing at your feet staring up at you, as they often do while i'm trying to tame them, you can punch them causing them to retaliate and steal from you. This didn't lower the taming effectiveness any, and don't worry too much about knocking it out as the tamkng progress doesn't drop while unconscious.
'You have been robbed! 5 fiber'
Ah, look at it run with the little bag
'You have been robbed! 3 wood'
I dont need that anyway
'You have been robbed! 100 narcotics'
O HELL NO
'You have killed! Pegomastax lvl 10'