G'day stillill,
There are approximately 6.5 million feral cats in Australia.
It has been estimated by the intelligentsia, that one feral cat alone will kill yearly, over 700 birds, lizards, and small quadrupeds each. That is a very conservative estimate at only 2 Australian native animals a day killed.
That will average out at about 4,500,000,000 small native animals killed each year by an ever breeding stock of feral cats...then we have the wild dogs that are decimating small and not so small quadrupeds, then there are the feral pigs...and camels, and donkeys.
I see the need to have any feral cat shot on sight, the same with feral dogs - Note Well: I don't see the Dingo as a feral dog.
The feral Cat is considered by nearly all, as a death machine, and to give you an idea of it's rapacious capacity, google Stomach contents of an Australian feral cat.
The above estimate is nothing when the gut tally of a feral cat is seen.