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The Long Road To Bringing Bison Back To Northern Colorado

It's a windy morning in early June, and Colorado State University researcher Jennifer Barfield is peering anxiously at a herd of bison. One is trying, really hard, to have a baby. Its her first birth, and the mama bison keeps laying down, then standing up, trying to get the calf out of her body.

Barfield takes another look at the mama, who is penned in with a small herd of other bison at the CSU Foothills Campus.

"The feet of the baby are sticking out about 3-4 inches, and she's pushing which is a good sign," she notes. Barfield's normally-smiling face is furrowed with anxiety though; the birth, which usually takes less than an hour, is moving too slowly. Today, she knows, is more than just a birth. It's the culmination of years of work.

A few veterinarians pull up in a pickup truck. One is carrying a dart gun. With the labor coming up on an hour and a half, they're planning to tranquilize the bison and pull out the baby. But another veterinarian, Jack Rhyan with the U.S. Department of Agriculture, wants them to wait.

"She's in good labor, you know," said Rhyan."I hate to intervene just yet."

Rhyan, who has the calm air and no-nonsense manner of an old-timer, seems confident that the mama can pull through and have a natural birth. While this is just the third live birth he's seen, he's worked with bison for decades. He's tracked this herd of 10 at CSU since it was first removed from Yellowstone National Park, in 1997. The group spent a few years in Idaho, and then, in 2004, was moved to Fort Collins, Colorado.

The mama bison slumps off to the most private part of the pen, a small shed, where she lays down. When she gets up, it's clear Rhyan's instincts were correct. A small, orange-colored bison calf lies beneath her. Barfield and Rhyan laugh with relief as they watch the mama lick the baby.

To understand why this birth is such a big accomplishment, you have to know a little about the history of bison in the United States. By the mid-1800s, the animals that once stampeded across a wide swath of the Great Plains and West were dwindling. In the 1870s, "bison were almost exterminated," said Rhyan.

Around that time, a few conservation-minded ranchers took it upon themselves to save small herds of bison. When the animals were declared a protected species, animals from those herds were sent to Yellowstone. The descendants of just around 200 bison saved by ranchers still roam the park today.

Other bison stayed in ranchers' herds, but many of these were bred with cattle. Today, herds of bison without cattle genes are considered special, because most herds in the United States contain bison with some cattle DNA.

Credit Stephanie Paige Ogburn / KUNC
Washing and thawing a frozen bison embryo in a lab at the CSU Foothills Campus. It will soon be implanted in a female bison.

The bison in Yellowstone, and in the CSU herd, do not have cattle DNA, at least as far as modern tests can tell, said the USDA's Rhyan. That makes them good candidates for reintroduction and breeding. But Yellowstone bison also have a major drawback. Many of them carry brucella bacteria [.pdf], which can cause abortions and reproductive problems not only in bison, but also in cattle. Jack Rhyan has worked for years to combat this disease, and has tested the CSU herd to make sure they are brucella free.

The likely presence of brucella in the semen of Yellowstone bison posed a problem for Jennifer Barfield, who wanted to help this small CSU herd breed and diversify their genetics. She hoped to use Yellowstone bison sperm for artificial inseminations, but it likely would carry brucellosis.

"When we have the opportunity to get sperm from new bulls we want to do that so we can maximize the diversity of our herd," said Barfield.

Reintroducing brucella-infected bison, however, is out of the question in an area where cattle might get infected. The CSU herd had to remain disease-free. So Barfield is using an innovative technique to get around the brucellosis problem. A centrifuge and washing process, originally developed to clean semen from HIV positive men, cleans the donations from the Yellowstone bison.

"So at the end what we get is a sperm sample from a bull that has brucellosis that no longer carries that bacterium," said Barfield.

The calf born in June was a product of artificial insemination using that cleaned sperm.

Credit Jim Hill / KUNC
The bison herd runs past a pregnant bison at Colorado State University's Foothills Campus, June 2015.

Barfield's team tested out another new way to impregnate the Fort Collins bison, using embryo transfer. Inside a lab at the Foothills Campus, Barfield gazed intently into a microscope as she thawed and washed a tiny fertilized embryo. She placed it into a straw and held it up; in about 10 months, this dust-sized dark speck could be a baby bison.

Those straws are loaded into what Barfield calls an AI gun, an 18-inch long, needle-like device with a plunger. A lab assistant slides the gun inside his shirt to keep the embryo warm, and Will Falbo, who works for Barfield, jumps into a car and drives the embryo a short distance over to some holding pens, where a female bison awaits.

It's hot, and the bison shakes in the metal squeeze chute, nose heaving and eyes glistening. The chute's goal is to keep her still, but she sits down on her back legs. She's not having it. After more coaxing, the cranky female stands back up and is still. Veterinarian Greg Ferrand dons a glove that reaches to his shoulder, reaches up inside the bison and starts digging. Falbo explains what's happening:

Credit Stephanie Paige Ogburn / KUNC
U.S. Department of Agriculture wildlife biologist Matt McCullum works to calm a female bison in a squeeze chute so she can be implanted with an embryo.

"So right now he is clearing out the intestines of feces because what he is going to be doing is guiding the embryo gun up through the vagina, kind of guiding it with his hand up the rectrum,"

With one hand inside the newly-emptied rectum, Ferrand grabs the AI gun, calls for some lube, and maneuvers it inside the bison. It's hard to find the spot in the uterus he wants, however, and Ferrand has to remove the gun and take another try.

"It's a very very small opening. it's like like threading a needle blind," said Falbo.

This bison's tense, or something. After nearly an hour of varied attempts, Ferrand finally gets the gun where he wants it and plunges down the embryo. They raise the gate, and the anxious female bolts out of the chute. Then it's time for the next one.

Credit Stephanie Paige Ogburn / KUNC
Zella Brink helps veterinarian Greg Ferrand implant an embryo into a female bison.

Come mid-November, Barfield will learn if this new technique worked, and if any of the female bison are pregnant.

A little sooner, though, she and Jack Rhyan will see another payoff. The city of Fort Collins and Larimer County agreed to host the CSU bison herd at Soapstone Prairie Natural Area and Red Mountain Open Space, just a short drive outside of town. The reintroduction of the Laramie Foothills Conservation Herd, as it is called, brings a smile to Jack Rhyan's face.

"So when I first saw Soapstone I just said to the people with me, 'this place is just crying out for bison,'" he said. "I mean you could almost see the Arapaho sitting on the hill, you know."

On a breezy summer day out in Soapstone's shortgrass prairie, this is a pretty easy picture to mentally paint. It's been a wet year, and the grasses are tall and green. The foothills loom in the distance, and the sky seems to stretch on forever. There's no bison here right now. Or maybe they're just over the hill.

Stephanie Paige Ogburn has been reporting from Colorado for more than five years, primarily from the Western Slope.
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