Conservation in action: Restoring North America’s bison population


Bison at Minneopa State Park // Photo courtesy of Minnesota DNR

Take a Sunday drive along the rolling county roads of outstate Minnesota, watching out your window as lakes and clustered cabins give way to sprawling farmland and the odd barn or cowshed, and you might spot among the dairy farms and cornfields the occasional ranch dedicated to raising bison.

From the safe side of a sturdy fence, these animals might look wholly foreign and unfamiliar living on a farm—especially compared to our mental image of the more commonplace cow—but today’s farm-raised bison aren’t the same as the beasts that once grazed the prairie stretching from Alberta, Canada, to Texas, and most of these bison aren’t so different from their cattle cousins.

Once numbering between 30 and 60 million, the great herds of free-roaming American bison were displaced from their native habitat by European and American settlers, reduced by grazing competition and cattle disease, and then hunted to near extinction by the end of the 19th century for their furs, hides, and bones.

Bison-Minneopa-15-2-by Scott Roemhildt

Bison at Minneopa State Park // Photo by Scott Roemhildt

When the American Bison Society was established in 1905 to conserve the species, fewer than 1,000 bison remained. The society created preserves and stocked them with bison from places like Yellowstone and the Bronx Zoo. Ranchers also joined the conservation effort, breeding their cattle with bison to introduce genetic diversity into the species and pursue a hybrid that could better withstand harsh winters.

The resulting crossbreeds looked like bison, but they topped out around 1,000 pounds—much smaller than pure bison, which often reach a full ton (2,000 pounds). Nevertheless, interbreeding did help the population recover; today, nearly 500,000 bison exist in public and private herds throughout Canada and the U.S.

MN zoo vet with bison

A Minnesota Zoo veternarian processes a blood sample taken from a bison // Photo courtesy of Minnesota DNR

Starting in 2006, Texas A&M’s College of Veterinary Medicine set out to determine the genetic diversity of these modern herds with the goal of seeing whether any modern bison remained free of cattle DNA. After testing hair and blood samples from across the bison population, including 35 bison at Blue Mounds State Park in Luverne, Minnesota, in 2012, researchers discovered that less than four percent of the world’s remaining bison—fewer than 20,000—were pure. Much to the surprise and delight of the Minnesota DNR, the herd at Blue Mounds, which is managed to stay close around 100 head, was among the few without any cattle genes.

Consequently, the Blue Mounds herd was identified as one that could help bolster North America’s population of pure bison. A successful restoration project would require careful management of the herd until it reached 500 head in size, the point at which a population can sustain itself, says Molly Tranel Nelson, regional resource specialist for the Minnesota DNR parks and trails.

In order to monitor genetic diversity and prevent contamination by cattle DNA, every autumn since 2012 Blue Mounds State Park has corralled the bison to collect more hair and blood samples. They usually remove a few bulls from the herd at this time, too. “You can’t have very many males in one place,” explains Nelson. One reason: “You have to make sure they don’t breed with their mothers, daughters or sisters.”

Bulls that are removed, especially those found to have even a trace of cattle DNA, are auctioned to private herds—ever had a bison burger?—where the animals meet what Nelson calls their “unfortunate fate.”

Unlike other animal-restoration projects, which often focus primarily on building up a population’s numbers, Nelson says this is about something more. “Genetics drive this project. [It’s] really about maintaining that genetic purity.”

Next page: Reintroducing bison at Minneopa State Park

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About Brendan Kennealy

Brendan Kennealy is a writing and PR professional who lives and works in St. Paul. Find him on Twitter here: @extrapalemale.

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