Tasmania's thylacine has been extinct for 70 years – or has it?

The Independent-- On a bright summer morning in the back end of Tasmania's north-west, I wandered into an office of Forestry Tasmania for advice about a forest dirt road. The sketch map the official offered was expected; not so his story. On that same track a decade or so ago, he had seen a creature that was not supposed to exist. And not just him; loggers and surveyors, an old-timer shacked up in the bush, all had glimpsed the animal before it slipped away into one of the most ancient rainforests on Earth.

Foresters are generally a practical bunch who measure life by certainties such as sawlogs and stray limbs lost to heavy machinery. When they swear to a sighting, you begin to wonder if there's truth after all to the Tasmanian tiger.

There are really only two things you need to know about the world's largest carnivorous marsupial. The first is that it looks nothing like its namesake except for the sandy orange coat and stripes that extend down to a stiff tail. The tiger – or thylacine as it is usually known because of its scientific name, Thylacinus cynocephalus, which means "pouched dog with a wolf's head" – is an evolutionary concept-creature that bolts the back half of a kangaroo on to a rangy dog the size of an Alsatian. The second is that it has been extinct for seven decades. Or it has unless you ask around. Then it turns out they're everywhere.

The first one I saw was in Hobart, the state capital. In the Tasmanian Museum and Art Gallery, a small crowd gathered around footage of a restless creature in the city zoo with a slender snout that opened to a snake's gape and a stiff gait that another believer later compared to a dairy cow. When "Benjamin" became history one chilly September night in 1936, he is thought to have taken the species with him.

Start to look, however, and a tiger will be there staring back at you. It gazed coolly from the label on my bottle of Cascade beer. It slinked into grass on the number plate of every car in front. And tigers rampant flanked the heraldic crest on state buildings – who needs unicorns when you have a home-grown fabulous beast?

No wonder tiger-hunters become obsessed. To the newcomer, Tasmania is the surprise of Australia. It is an island of hidden secrets in a nation of infinite space; a place where real-life devils utter banshee wails and moss-bearded giants stand silently in forests that predate mankind. In this Middle Earth of lost myths, a legendary tiger is just part of the scenery, and there's a lot of that to cover in a state that's one-quarter wilderness.

Many otherwise eminent people have suffered ridicule and nights cooped up in a chicken shed with a camera in their pursuit. The government's Parks and Wildlife Service mounted its own two-year hunt in 1984 before it pronounced the species extinct and devoted its energies to finding feral foxes instead. That only upped the ante.

"Parks don't want to say anything publicly to attract attention," Ned Terry confided. We were drinking coffee in Deloraine in the state's north, where farming villages were scattered over my map like seed and the landscapes are so vivid that the first pioneers christened their settlements Eden, Paradise and Promised Land. Hard to believe that the Alpine wilderness of Cradle Mountain lay an hour's drive south. "The bush was full of tourists after a national park fellow reported a thylacine on the central east coast a few years ago. But those blokes got a lot of cameras out there to look for foxes. I wouldn't be surprised if there's some skulduggery going on."

In this zoological X-Files, the 80-year-old bushman plays Mulder. Every couple of months he listens patiently to an excited witness, asks a few questions to weed out the fakers, then follows up whoever is left. His latest credible lead in half a lifetime's tiger-chasing came from Lake Peddar in the south-west wilderness.

"Fellow camped out there says he heard one for three weekends in a row; that yapping noise they make when hunting. Says it ran so close he could smell it."

Many witnesses mention the smell – a sharp, hot, animal stink that electrifies the air. "Smelled it myself once," Terry said. "Makes the hairs on your neck stand on end, I can tell you."

The truth is out there, somewhere. Probably (I dragged out of Terry) in the remote northern corners of the state. So, in the late afternoon I rolled east over swells of grass bound for Scottsdale. Every so often a timber farmhouse heaved aloft on a crest then vanished into the rear-view mirror. Beyond lay the high country of the north-east.

Around seven thylacine sightings a year, more than anywhere else in Tasmania, were made up there in the half-century after Hobart Zoo lost its star attraction. A few tiger-hunters still came to shoot blurry images, stalking the edge of old-growth rainforest that had barely changed since Tasmania ripped away from the global supercontinent of Gondwanaland.

In the pub I met a farmer who yarned about a wolfish head that had poked through the bracken fern. "When he comes out he sits up like a kangaroo, then starts sniffing the air like one. I thought: 'What the hell's that?'" A stray dog, perhaps, I suggested. "No dogs up there," he bristled.

It turned out the area was swarming with rumours. Craig Williams, Tasmania's premier wildlife guide and a fourth-generation bushman, kept up a rumble of anecdote and oath as we skirted the forest, stopping occasionally to practise an arcane element of bushcraft or stare after a furry backside that disappeared into the scrub. He indicated a farmstead as we swerved around one corner. "You know the last thylacine died in 1936? An old bloke shot one there in 1946. Said it was killing his chooks [chickens]."

Later, after a meal that belonged to a Sydney restaurant rather than a remote mountain shack, Craig told tiger tales around the campfire. There was the thylacine witnessed by four people on a logging road just over that ridge, and the waxy scat found late last year by the manager of a wilderness lodge. Or there was his mate whose car had broken down up here one night: "He said he heard these high-pitched yaps following him as he walked."

Apparently Craig's grandfather and great-grandfather used to trap thylacine on the mountain behind us. I tried and failed to reconcile the mysterious thylacine with the plantation forest that now striated its flanks. Could it really survive here?

As the sky deepened to a velvety black, Craig strobed the treeline with a torch. There were secrets as well as possum eyes in the dark spaces between eucalyptus trunks. Suddenly, at the edge of our clearing, something twitched. A stoat-like animal froze in the torch's beam then skittered into the bush – a spotted-tailed quoll.

"Amazing killing machines; the ultimate predators," Craig said with admiration. "They're only a few kilos, but they can pull down a wallaby." With jaws that opened to 90 degrees and overlapping teeth, it was a distant relation of the thylacine colloquially known as a tiger quoll. "Been quite a few tiger sightings by quite a few people made around here."

I'd lost my bearings way back on the unmarked dirt roads. "Good," said Craig. "I don't want loads of people running around with traps and cameras. If the tiger's up here, let him be. That's what I reckon." Another Tasmanian secret was safe.