For five months last year 1,500 kilometres, 300 rolls of film and 50 hours of videotape Karsten Heuer and Leanne Allison followed the Porcupine caribou herd on foot.

Through the waist-deep snows of April, across the mighty waters of the Firth and other rivers and creeks, smothered by the bugs of summer, from Old Crow to the calving grounds on Alaska's North Slope and back, the couple followed.

Heuer and Allison had adopted a kinship with the Porcupine caribous' situation, her through working on a film with the Gwitchin people in Alaska and him through his two years as a park warden for Ivvavik National Park in North Yukon.

The married couple, both 35, wanted to tell the caribous' story.

'We figured the only way we could do that was try to be caribou,' Heuer says in an interview Monday in Whitehorse. 'Walk a 1,000 miles in their hooves.'

Heuer and Allison, northern B.C. residents, will host a one-hour presentation about their journey at the Yukon Arts Centre tonight.

Their intent, they emphasize, was clearly to document the harshness of the caribous' life, and to show why, in their eyes, it is critical oil and gas exploration not be allowed on the herd's calving grounds.

The couple arrived in Old Crow early last spring. They departed the Gwitchin community on April 9 with a man who had been out hunting caribou the day before.

He left them at the confluence of the Bell and Porcupine rivers, in the company of caribou.

As they began to move north with a single pocket of the herd that numbers 123,000, it was difficult going. The snow was soft and deep, rendering their cross-country skis ineffective.

They were forced to follow in the troughs left by the caribou.

It was, says Allison, like balancing on a log with 30-kilogram packs on their backs, kilometre after kilometre, until they were through the stretch along the Richardson Mountains.

'These animals are built to travel,' she says. 'What made this trip different than any other trip we had been on is we had no planned route ... we just let the caribou guide us along the way, and they were really great guides.'

The snow eventually became wind-blown and hard, allowing for the use of their skis and making it easier to keep up.

'We would be with a group, and we would kind of lose them and then another group would pick us up,' Heuer recalls.

There were times during the migration, however, when they would remain with the same bunch for seven or eight days.

While difficult to estimate because of the sheer numbers, some of the groups they attached themselves to were likely in the order of 5,000 to 6,000 animals.

Nothing was ever the same. It wasn't an eight-hour day.

They moved when the caribou shifted, and rested when the caribou paused, night or day.

Allison and Heuer remember once when the caribou began moving just as they woke. They broke camp quickly, only to watch the group stop for several more hours just a stone's throw away.

It was in late May as they were still moving northwest toward the calving grounds that Allison came closest to calling it quits. That happened after a scrawny grizzly bear had followed their trail with its nose right into camp.

A bear banger did nothing to deter the animal. They had brought no firearms.

It was only after Heuer picked up the tent to make himself appear somewhat formidable, and began thrusting it toward the bear, that it lost interest. But it only meandered away slowly, showing no signs of feeling threatened.

But by that time, Allison had almost lost her nerve, but didn't. It was, for her, a heightened awareness that she and Heuer were part of the food chain in their circumstance, just like the caribou.

The entire journey, says Heuer, was an inspiring insight into the lives of the Gwitchin's nomadic ancestors.

They forged rivers and creeks, sometimes at high water, sometimes with sills of ice still running along the banks.

They swam the Firth, and used ropes to pull their packs across.

Food arrived every two or three weeks by aircraft, though often delivered for free by researchers and field workers who knew of the trek, and understood it was more than recreational.

From June 1 to the 10th, Heuer camped on the Porcupine herd's calving grounds. They never left the tent, even relieving themselves in cups. Conversation was held to whispers.

All the way north, the caribou had not been bothered by their presence.

It was an entirely different atmosphere on the calving grounds, when the caribou were on full alert.

There wasn't much predation, as the bears and wolves were still in the hills, for the most part. The bugs hadn't yet arrived in numbers.

But the cotton grass the cows depend on for essential milk production was plentiful.

It is those 10 days every year that will determine the health of calf. It's says the weight the calf gains in the days after birth before beginning the migration south will be reflected in the animal's adult size.

Heuer says it's no coincidence the caribou have chosen the coastal plain in Alaska's Arctic National Wildlife Refuge to have their calves. Predation is low, there are no bugs and food is abundant, he says.

Allison suggests it's nonsensical to think that such a sensitive setting would not be disturbed by oil and gas exploration, the presence of drilling platforms, airstrips and roads.

Industry, Heuer points out, maintains advancements in technology will allow it to be unobtrusive, though he doesn't buy it either.

Industry, he adds, keeps pointing to the healthy status or the Arctic central herd, whose range includes the Prudhoe Bay area, the focal point of Alaska's oil and gas industry.

The Arctic herd, however, had an alternative to Prudhoe Bay when it was displaced by industrial activity, says Heuer, adding there is no alternative calving location for the Porcupine herd.

The cotton grass the cows depend on is only found on the plain, Allison insists.

Heuer says 95 per cent of Alaska's north coast has been made available to the oil and gas industry.

The calving grounds, the 1002 lands that industry and Alaska's Republicans are pushing to open up for exploration, represent five per cent, he says.

Humankind, Heuer says, has an obligation to balance its needs with the needs of others it shares the planet with.

'So I see no reason why it has to be 100 per cent,' he says of the push to open of the calving grounds to exploration, 'especially when you see what the caribou have to go through to get there, and what they need for survival.'

After all, Allison suggests, it is says the 1002 lands hold but a mere six-month supply of oil at the current rate of U.S. consumption.

The stay on the calving grounds is brief, and the caribou are on the move back south and into the hills as the bugs begin to arrive.

For Heuer and Allison, it wasn't so bad as they were equipped with mosquito netting for themselves and their tent.

For the caribou, it was like nothing they've witnessed.

'Just the way they drove the caribou batty was something to see,' he says. 'It's actually mind-boggling.'

Heuer says the caribou moved quickly from one ridge to another, in search of a breeze strong enough to keep the bugs in check, and they knew where those ridges were.

The couple arrived back in Old Crow on Sept. 8, tired and each 11 kilograms (25 pounds) lighter, their bones aching.

They had long passed their point of peak physical condition and were on the downward slide.

But it was just three days later when they arrived in Washington, D.C. as part of the ongoing lobby effort to ensure continued protection for the calving grounds.

'We did this to try and feel the geographical and ideological difference between where the caribou live, and where these decisions were being made,' says Allison.

So fresh were they from the trail of the Porcupine caribou, she quips, that they were still looking for tracks through concrete parking lots in the U.S. capitol.

Their contribution to the internationally-charged issue of the 1002 lands will be their story, the caribou story, maintains the couple. They are visiting four Whitehorse schools in addition to tonight's public presentation, which will start at 8:00.

Heuer is also writing a book about their experience, for which he received an advance which helped cover the $65,000-cost of the journey.

Allison is currently working on a film documentary with the National Film Board of Canada, which has purchased exclusive rights to the video footage.