The Yukon's one and only wood bison herd is a poster child for the restoration of endangered species. But wood bison had a close call with extinction, and wildlife managers are still keeping a eye on them.

A seed group of bison was brought to the territory in the spring of 1986. The herd descended from them now averages about 450 healthy animals and reproduces at a rate that allows an annual sustainable harvest.

That harvest is a major factor in the herd's success, says Michelle Oakley, Kluane regional biologist for Yukon Environment.

"A lot of the success of this program comes because this herd is being sustainably used by Yukoners and is therefore valued by Yukoners, locally and in Whitehorse or elsewhere."

"Locals are certainly the best wildlife stewards you can have, and in this case, they were asked not just to protect these animals, but were given the opportunity to use them sustainably," says Oakley.

The bison harvest feeds a lot of Yukoners, she adds, and gets a lot of families out on the land together. In addition, several school or educational hunts have allowed kids to learn about traditional life and culture, as well as about the natural history of the bison.

Wood bison, a northern subspecies of the American bison, occur only in Canada, and the Yukon herd is a substantial portion of the total population of roughly 3500.

That population is a mere remnant of the bison that once inhabited Canada's northern forests. Historians and scientists estimate the wood bison population was more than 168,000 before 1800.

Hunting, disease, and loss of habitat whittled away at the numbers until, by 1888, there were only about 500 left, mainly in the southern Northwest Territories. In 1922, Wood Buffalo National Park was established to save them from extinction and protect their habitat.

Ironically, the wood bison almost disappeared again, thanks to the success of another breeding program. In 1928, 6600 plains bison were shipped to Wood Buffalo park to relieve overpopulation at Elk Island National Park and Wainwright Buffalo Park in Alberta.

The result, as several biologists warned, was interbreeding that almost eliminated the wood bison subspecies. In addition, the plains bison brought with them tuberculosis and brucellosis, two diseases they had picked up from domestic cattle.

In the 1960s, Oakley says, a few remaining isolated wood bison herds were found in the northern corner of Wood Buffalo National Park. About 70 animals were sent to Mackenzie Bison Sanctuary in NWT and later about 21 wood bison were sent to Elk Island to start another herd of wood bison.

The Yukon's Aishihik herd developed from about 170 individuals derived either directly or indirectly from the Elk Island population.

At this stage, the Yukon herd is a success. It's one of two disease-free herds that have reached what the national wood bison recovery team considers a viable size of over 400 individuals.

But that doesn't mean it's necessarily secure. One of the pitfalls of restoring species that have shrunk to just a few dozen individuals, as the wood bison did in the 1960s, is that everyone is related to everyone else, leading to a very limited range of genetic material.

"For the short term, the Aishihik herd seems to be doing well and reproducing at normal rates," says Oakley. "But for the long term or in the face of any new disease or challenge to their survival, will they have the variation to survive?"

The need for genetic diversity is something currently being considered by the national wood bison recovery team, of which Oakley and Thomas Jung, senior biodiversity biologist at Yukon Environment, are members.

Genetic diversity is a huge issue in restoring populations, Oakley says. There are numerous examples of health problems arising from inbreeding, both in wild animals like the Florida panther or black-footed ferret and in domestic animals like some breeds of dogs and cats. Fortunately, she adds, we are developing ways to improve genetic diversity.

"For example, artificial insemination is one tool that wildlife vets and conservation biologists are using in some species to share and improve genetic material. The advantage with AI is you can bring the material and not bring the animal (and all its potential diseases and parasites)."

For more information about wood bison and breeding programs, contact Michelle Oakley, Kluane regional biologist for Yukon Environment, at (867) 634-2439 or Michelle.Oakley@gov.yk.ca.