John, dead vermin species have been hung on wire fences for as long as I have been travelling in the country, many decades...I've seen wild dogs (feral and dingo) and foxes, rabbits, crows and eagles (a real shame), and cats. I'm surprised not to see flesh ripped off the carcasses in these fine shots of yours, must not be many hungry large animals out there..feral pigs and goannas would crunch up almost all of these animals, especially since they were skinned - fast food!.
I think the act of hanging them is both a social statement about these animals and a warning to other animals of the species.
Not to preach but I heard a wildlife specialist saying today that cats (feral and 'semi-feral' house cats) kill several million mammals, birds and reptiles each *week* in Australia. The north of Australia is losing species faster than anyone in the field can understand or comprehend. Half the species made extinct in recent years in the world occurred in northern Australia.
Finally, fine images, thanks for posting.