Murray, the roo does have it's eyes on the subject. If you have ever seen roos boxing, this is exactly how they do it.
Their head goes right back, balance on the tail and box quite furiously in spurts.
In the fifties there was at least one travelling boxing show in a tent. This troupe of boxers never went too close to the cities as the side bets which were part and parcel of these, were illegal.
The particular boxing side show I remember, is one with a large Eastern Grey male kangaroo as their star boxer. I never saw that roo lose a bout in at least two times and possibly a third time I attended.
Camping in the bush in the sixties we often heard roos boxing in the distance. Usually in the early hours of the morning and the late afternoon. Occasionally we saw them, always exciting, especially if they were mature males, then you got to see some really tough stuff.
Mick.