What is this creature that by itself threatens an entire industry, inflicting several millions of dollars of damage a year despite the presence of the world’s most obsessive fence? Cousin to the coyote and the jackal, descended from the Asian wolf, Cam’s lupus dingo is an introduced species of wild dog. Skeletal remains indicate that the dingo was introduced to Australia more than 3,500 years ago probably with Asian seafarers who landed on the north coast. The adaptable dingo spread rapidly and in a short time became the top predator, killing off all its marsupial competitors. The dingo looks like a small wolf with a long nose, short pointed ears and a bushy tail. Dingoes rarely bark; they yelp and howl. Standing about 22 inches at the shoulder – slightly taller than a coyote – the dingo is Australia’s largest land carnivore.

The woolgrowers’ war against dingoes, which is similar to the sheep ranchers’ rage against coyotes in the US, started not long after the first European settlers disembarked in 1788, bringing with them a cargo of sheep. Dingoes officially became outlaws in 1830 when governments placed a bounty on their heads. Today bounties for problem dogs killing sheep inside the Fence can reach $500. As pioneers penetrated the interior with their flocks of sheep, fences replaced shepherds until, by the end of the 19th century, thousands of miles of barrier fencing crisscrossed the vast grazing lands.

The dingo started out as a quiet observer,’ writes Roland Breckwoldt, in A Very Elegant Animal: The Dingo, ‘but soon came to represent everything that was dark and dangerous on the continent.’ It is estimated that since sheep arrived in Australia, dingo numbers have increased a hundredfold. Though dingoes have been eradicated from parts of Australia, an educated guess puts the population at more than a million.

Eventually government officials and graziers agreed that one well-maintained fence, placed on the outer rim of sheep country and paid for by taxes levied on woolgrowers, should supplant the maze of private netting. By 1960, three states joined their barriers to form a single dog fence.

The intense private battles between woolgrowers and dingoes have usually served to define the Fence only in economic terms. It marks the difference between profit and loss. Yet the Fence casts a much broader ecological shadow for it has become a kind of terrestrial dam, deflecting the flow of animals inside and out. The ecological side effects appear most vividly at Sturt National Park. In 1845, explorer Charles Sturt led an expedition through these parts on a futile search for an inland sea. For Sturt and other early explorers, it was a rare event to see a kangaroo. Now they are ubiquitous for without a native predator the kangaroo population has exploded inside the Fence. Kangaroos are now cursed more than dingoes. They have become the rivals of sheep, competing for water and grass. In response state governments cull* more than three million kangaroos a year to keep Australia’s national symbol from overrunning the pastoral lands. Park officials, who recognise that the fence is to blame, respond to the excess of kangaroos by saying The fence is there, and we have to live with it.