After more than 100 years of absence from the United States, a wild population of North America’s largest land mammal may soon be reintroduced to Alaska: wood bison.

Larger than plains bison (Bison bison bison)—which may weigh up to 1,900 pounds—wood bison (Bison bison athabascae) bulls tip the scale at up to 2,250 pounds. The shaggy-coated wood bison, however, have short horns that extend sideways and back from their heads, while the horns of their “cousins” on the plains are much larger.

Wood bison lived in Alaska for most of the past 5,000 to 10,000 years, but they had virtually disappeared by 1900. Habitat changes during the Holocene period and hunting are thought to be the major factors in their decline.

Canada has successfully established seven free-range, disease-free wood bison herds within its borders, resulting in the reclassification of the wood bison from endangered to threatened under the Endangered Species Act. The planned, experimental population in Alaska is part of an attempt to ensure the animals’ long-term survival.

But can this “rewilding” succeed in a state that already has numerous megafauna species and other competing strains on its natural resources?

Yellowstone National Park’s wolves are an example of successful rewilding. ©Gary Kramer/USFWS, flickr

Bringing back a bygone bison

Rewilding is a conservation practice that involves reintroducing keystone species and apex predators to areas where they have become extinct. The reintroduction of wolves in Yellowstone is a successful example of rewilding.

The Alaska Department of Fish and Game has been involved in evaluating and planning the reintroduction of wood bison since 1991. In 2008, 50 bison from Canada were imported to supplement a smaller herd already being held at the Alaska Wildlife Conservation Center in Portage, about 20 miles south of Anchorage. Today, that herd has grown to about 130 animals.

Working with the U.S. Fish and Wildlife Service, the department identified three areas in central Alaska where the wood bison could be reintroduced: in Yukon Flats, Minto Flats and the lower Innoko-Yukon River area. The first release was scheduled for spring 2010 in Yukon Flats—the last place wood bison were known to roam in Alaska in the 1800s—but the effort had to be abandoned since that area is now a national wildlife refuge.

Reestablishing keystone grazing herbivores can help restore Northern ecosystems. ©Henry H. Holdsworth

The state’s second-preferred release site, Minto Flats, about 20 miles west of Fairbanks, was shelved because of concerns about conflicts with future gas and oil development raised by Doyon, Limited. The current plan is to release the first wood bison in the Innoko-Yukon River area in southwest Alaska.

It is hoped that such a release will not only increase the worldwide population of wood bison, but that it will reestablish a keystone grazing herbivore to what was once a natural-grazed ecological community, helping to restore the Northern ecosystem.

A much-changed world

When environments lose their large herbivores and predator species, the niches those animals once inhabited are left unoccupied, creating an imbalance. Much of North America’s native flora and fauna evolved under the influence of large mammals. But critics of rewilding wood bison to Alaska say that it is unrealistic to assume that natural communities today are functionally similar to their state more than a hundred years ago. They argue that evolution doesn’t stop just because one particular species is removed from a system, and thus the reintroduction of a large mammal could thwart current ecosystem dynamics and possibly cause collapse. Under this premise, the new wood bison would be considered “exotic” and could potentially harm other native North American species through invasion, disease or other means.

The spring browsing of willows by wood bison may overlap the forage needs of moose. ©Eric Rock

It’s true that within the historic range of wood bison, there is some potential for the animals to compete with existing large ungulates for forage, providing that both species occur in the same area and the forage item is limited. For instance, the wood bison’s fall use of terrestrial lichens may overlap the forage needs of caribou, and spring browsing of willows may overlap the forage needs of moose. Too, wood bison herds may indirectly influence predation rates on moose by supporting higher wolf densities than would exist without the presence of wood bison.

The Fairbanks Daily News-Miner reports that the released wood bison would be classified as a “nonessential, experimental” population, which means that there will be no designation of land for them as critical habitat. Their reintroduction, then, will not be able to hinder development, including oil drilling or mining.

Do you think that the reintroduction of a megafauna species can succeed in an area that already has a good number of large animals, particularly if no land will be set aside for it as critical habitat?

Here’s to finding your true places and natural habitats,

Candy