As if in some B-movie thriller, people here are raising a hue and cry about an alien predator that is spreading out of control across the land: a plague of millions of killer house cats run wild.

Interlopers on this isolated island continent like the settlers who brought them here 200 years ago, stray cats have multiplied through Australia's deserts, forests and urban alleys, driving indigenous species to extinction as they go.

Without any natural enemies to keep them in check as on other continents, perhaps 12 million wild cats have been killing small creatures whose evolution has not taught them that cats are their enemy.

Extinct already, or living only in zoos, are the pig-footed bandicoot, the brush-tailed bettong, the rufous hare-wallaby and a dozen other birds and marsupial species that were found nowhere else on earth.