In the early 1800s, at least 30 million plains bison (Bison bison bison) covered the prairies of the U.S. and Canada. By 1876 there were fewer than 100.

At one time on the verge of extinction, bison have staged an impressive comeback. (photo: Environment Yukon)

"That is the equivalent of exterminating the entire Canadian human population and leaving about 80 wild humans," said Wes Olson, senior warden of Alberta's Elk Island National Park.

Olson was in the territory last week give a lecture for the Yukon Science Institute, From Whence They Came: The History of Canadian Bison Conservation.

Not surprisingly, his presentation featured many painful moments, such as iconic slides of a mountain of bison skulls, and of their bleached bones covering an empty, haunted prairie.

When Europeans began settling the continent, plains bison could be found as far east as Kentucky and even up into Delaware.

Those herds vanished very quickly, said Olson.

However, the techniques of slaughter were truly perfected more than a century later on the Great Plains.

After the U.S. Civil War, land-hungry settlers swarming into the West, converted huge swaths of bison habitat into farmland. But, of course, it was the hide industry that really did the beasts in.

British tanners had discovered that alum could be used to create a more durable leather. With the improved product, the market boomed.

Between 1870 and 1876, on one U.S. railway alone, two million hides were shipped east each year, said Olson.

"They estimate that for every hide that made it to market, at least two or three were wasted and left on the field," he added.

By 1892, further to the north, about 170,000 wood bison (Bison bison athabascae) also disappeared.

"We don't know what originally happened to the wood bison, but the population crashed to about 250 animals," said Olson.

Some people believe that the hide hunters moved north after the plains bison were killed off, he said. But having studied the terrain favoured by wood bison here, Olson finds it difficult to believe that such a through harvest of wood bison would have been practical, or even possible.

Efforts to mitigate the plains bison calamity began even before the slaughter had run its course.

Samuel Walking Coyote of Montana's Flathead Reservation launched the recovery process in Montana in 1873, when he began building a herd from four young animals. He eventually sold his bison to Michel Pablo and Charles Allard.

In 1906 the Canadian government bought 716 of their animals and had them shipped north into what is now Elk Island National Park in Alberta.

That roundup was "a media circus," Olson said. There were plenty of witnesses as wranglers struggled to create some order out of the masses of feral beasts.

Rounding up the bison for shipment was a dangerous job. Olson, who is also a bison rancher, knows all-too-well what those old cowboys went through.

While helping to subdue an angry bull, his "horse almost ended up with a spare anus he didn't need," he said.

Eventually, the bison reached Alberta, where they prospered. In fact, they soon threatened to overwhelm their new home. A slaughter was considered, but strong public opposition led to a search for other strategies.

Apparently there were no easy answers. Almost 7,000 animals were shipped north by railway and barge to the eastern edge of Wood Buffalo National Park. Perhaps half survived the trip.

It was naively believed that thick spruce forests and wide rivers would prevent the plains bison from reaching their taller relatives, the wood bison who roamed on the other side of the park.

Alas the newcomers were made of more hardy stuff.

"It didn't take long until they found long, interconnected meadow systems through which they traveled west," said Olson.

And the rivers posed no serious obstacles because bison can swim.

By the 1930s a bison hybrid had begun to appear, as well as brucellosis and bovine TB carried north by the plains bison.

It appeared that the pure wood bison was a creature of the past.

A miraculous reprieve appeared to have been granted in 1959. An isolated herd of wood bison was discovered in the far northwest of the park on the Nyarling River. Eighteen of these bison were shipped south to Elk Island. The herd that now graces the southwestern Yukon is descended from these animals.

The first 34 bison were shipped from Elk Island to the Nisling River valley in 1986. By 1992, 142 bison had been shipped to the territory.

The Yukon herd, now numbering 500 animals, is by far the biggest success story in the recent history of bison conservation, said Olson.

Not only are the numbers impressive, but thanks to careful breeding practices back at Elk Island and careful monitoring here, the herd is free of TB and brucellosis.

Hunting and old age are the only major threats the animals face, said Olson. Even the wolves haven't mastered the art of killing bison.

Anyone interested in learning more about bison will want to keep an eye out for Olson's new book, Portraits of the Bison: An Illustrated Guide to Bison Society.

It features photographs by Johane Janelle and will be released by University of Alberta Press later this spring.