Bound for Montana, plains bison are loaded onto a truck at Elk Island National Park in Alberta.
After more than 100 years of trying to preserve the bison in North America, conservationists are relocating 70 of the species from Canada to their ancestral home in Montana – the second such move in three years.
The plains bison – 35 female and 35 male – come from Elk Island National Park in Alberta, where herds of the animals have been raised in conservation since the species faced near global extinction in the early 20th century.
"It's really been recovery central for plains bison and wood bison in North America," said Stephen Flemming, superintendent at Elk Island National Park.
Despite a previously abundant bison population on the continent, overhunting and the settling of the West in the late 1800s all but wiped out the animal, leaving fewer than 200 by the turn of the century. In response to the dwindling numbers, several private citizens in Canada and the United States began herding bison in an attempt to preserve the species.
In 1906, the government of Canada bought one of these herds from a private owner in Montana and over several years moved the animals to their permanent home in the parkland. Now, the Elk Island herd averages around 500 a year, including a surplus that allows Elk Island to share the wealth with other growing conservation areas across the continent.
This year, and once before in 2010, the American Prairie Foundation wildlife reserve in Montana was the recipient of the calves, in a unique homecoming to the bison's ancestral land.
The calves, born last spring, left Alberta by transport truck Tuesday afternoon.
"We send out just young ones because they're the guys that can travel well and they're the ones that are better for building up a new herd," Mr. Flemming said
"Big guys can harm themselves or each other."
Once in Montana, the calves will join APF's existing herd, topping off the population at more than 210. The reserve is home to many other native prairie animals, including ferrets, prairie dogs and hawks and is constantly growing as the APF acquires more land, according to Alison Fox, partnership and marketing manager.
"Our goal is to eventually create a nature reserve of 3.5 million acres ... of rolling hills and native prairie land," Ms. Fox said.
The success of the herd is especially important because there are still very few wild bison left, according to Cormack Gates, a biology professor and bison expert at the University of Calgary. Wild herds are not to be confused with domesticated bison, which are farmed for food and often a crossbreed with cows, he said.
"When humans intervene, when we start taking care of things like mate selection ... we've removed the natural selective forces that shaped the bison in the first place," Prof. Gates said.
"The wild herds that are left exposed to all of the vagaries of nature are the ones that will continue the evolutionary path for the species."
With a healthy herd of about 450 plains bison still remaining in Elk Island, Mr. Flemming said this trip is a special marker.
"We couldn't be happier to send them back home to Montana," he said.
"It's very exciting. We'll never be back to millions of bison, of course, but to have many thousands of bison will require private land ownership and what we're seeing in Montana is that this can be done."