We assume there were only a small number of animals as area of disturbed ground was limited. A bull and sheep from a neighbouring paddock were found on the reserve about 3 weeks ago. Could they have been responsible?
Does not look 3 weeks old. Not echidna. Looks like wombat. But usually there would be wombat footprints visible. On closer inspection, is that a cloven hoof print in 2nd photo? If it is a hoof print, I'd be thinking feral pig, sambar or fallow deer, but if so, this style of digging is atypical for those species.
Also consider human and EGK. Kangaroos sometimes dig like that for salt, and if they find salty soil, in time can make holes 60cm deep. Or maybe you have a 10 kg pink rabbit?
I have seen extensive disturbance of this kind in the Bullock Paddock Road area not far from Uriarra Village. We found a pig trap there while monitoring plantings in this area which left us thinking that pigs were responsible.