They protect these areas and clans from outsiders, and for good reason.
That sounds like a good possibility CE.Also, I wonder if our indigenous people had less food at certain times (drought, flood or seasonal changes in the harsh Australian climate) and the yowi became a food source. Or, visa versa - the yowie's food supply may have been depleted at certain times (due to the same causes), so I wonder did they come to regard humans as 'good eating' and easy prey, out of necessity? - which may have resulted in the indigenous people retaliating and 'making war' on them. (Thinking of how Chimps were thought to be vegetarian for a long time, until someone observed them killing and eating meat.)