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Scientific Progress Could Help Share Yellowstone National Park's Pure-Bred Bison With Other Sites


The baby bison and his mother at the Bronx Zoo (Photo courtesy of Julie Larsen Maher/WCS )

One small bison calf born in New York is causing a big stir in the wildlife conservation and scientific communities, and for good reason. He could represent a breakthrough in efforts to introduce genetically pure bison from Yellowstone National Park to other parts of the country.

Yellowstone is home to some of the few genetically pure bison remaining in North America. There's no shortage of sites eager to accept Yellowstone bison, but a long and complicated battle that mixes politics, economics and science stands in the way of potential transfers of surplus animals. At the root of the problem are fears by the cattle industry that animals from the park could spread diseases, including brucellosis, a disease that can cause spontaneous abortions among domestic livestock, to commercial herds.

Now a scientific breakthrough may offer an solution that creates genetically pure and disease-free bison from the Yellowstone herd.

American Bison - A Species Back from the Brink

Over a century ago, a source of bison wasn't a problem. In the 1800s, tens of millions of wild bison (often called "buffalo") roamed North America, but by 1900, their numbers had been reduced to fewer than 1,100 animals.

Thanks to a successful program to reintroduce bison to parts of their former range, hundreds of thousands of the animals are now found in state and national parks, wildlife refuges, and on tribal and private lands. However the vast majority of present-day bison are "hybrids" with domestic cattle genes, the result of efforts by western ranchers to create a hardier breed of cattle. Bison from Yellowstone National Park are among the few genetically pure animals left in the country.

Genetic Purity Matters

The concern with genetic purity isn't just a matter of scientific stuffiness. As bison were cross-bred with domestic cattle, they began to lose some of the behavioral traits that helped the animals survive in the wild. The domestic-bison mix animals can also have differences in physical appearance, such as the absence of the signature "hump" on the backs of adults.

A number of groups, including Native American Tribes and private conservation organizations, would like to reintroduce truly wild and genetically pure bison to their lands—if the animals were available.

A New Source of Disease-Free Yellowstone Bison

Now, thanks to a scientific breakthrough and collaborative effort by Colorado State University, the Bronx Zoo, the American Prairie Reserve, the Animal and Plant Health Inspection Service of the U.S. Department of Agriculture (USDA) and others, there's hope for a new source of genetically pure and disease-free bison.

The project began with the movement last fall of two separate groups of bison. The first included the transfer of about 30 bison from Yellowstone National Park to the USDA, where they were quarantined at a closed facility in Fort Collins, Colorado. This "restoration herd" provided a source of genetically pure—but not necessarily disease-free—animals.

A second small herd from the American Prairie Reserve was sent to the Colorado State University's Animal Reproduction and Biotechnology Laboratory facility in Fort Collins, Colorado. This group, which was disease-free but not genetically pure, would serve as eventual recipients of fertilized embryos from Yellowstone cows.

Embryo Science Breakthrough

Last October, an embryo was non-surgically removed from one of the Yellowstone bison and then chemically "washed" by scientists from Colorado State University (CSU) to remove any risk of disease such as brucellosis. CSU reproductive physiologist Dr. Jennifer Barfield and her team then nonsurgically implanted the embryo into the uterus of a healthy bison from the American Prairie Reserve herd which served as a surrogate mother for the hoped-for calf.

Finally, this surrogate bison cow was transported, along with 15 other bison donated by the American Prairie Reserve to the Bronx Zoo, which is operated by the Wildlife Conservation Society (WCS). Those bison will be serve as future surrogate mothers as the program grows.

Two months after the transfer, an ultrasound exam confirmed that the cow was pregnant, and a healthy male purebred bison calf was born at the zoo on June 20 this year.

The First of Many?

One small calf may not sound like a big deal, but his arrival was hailed by wildlife experts and scientists as a potential breakthrough in efforts to restore genetically pure bison to other parts of the country. He could represent the first member of a new breeding herd that could eventually help "stock" multiple sites around the country.

“The Bronx Zoo has been working for years to secure pure bison to establish a breeding herd that could supply animals for restoration programs,” said Dr. Pat Thomas, Wildlife Conservation Society Vice President/Bronx Zoo general curator and associate director. “Dr. Barfield and her team have provided an innovative way to rescue these valuable genes and allow us to create this important herd.”

“This science illustrates that we can engineer breeding of pure-bred bison to be disease-free despite the diseases that can afflict the bison population at Yellowstone,” said Barfield, an assistant professor in the university’s Department of Biomedical Sciences.

"In Yellowstone, the bison do not have trouble reproducing,” Barfield said. “It's the process of removing animals that have been exposed to disease from the park so that their valuable genetics can be incorporated into other herds or used to create new herds that is the problem. The Bronx Zoo has been a wonderful partner in this along with the American Prairie Reserve and the Animal and Plant Health Inspection Service of the USDA.”

Hopes for an Expanded Program

Now that a successful test of the process has been completed, there are plans to expand the effort to a larger number of animals this fall, and the method could benefit other species as well.

"This could be used for a lot of different species. It provides us a way to create new offspring where it was previously impossible or very difficult. We're able to create new animals that can be used by zoos starting herds and to help expand populations that need it," Barfield said. "The possibilities are endless."

Perhaps, over time, this effort could also help spell an end to decades of legal wranging about effors to share Yellowstone bison with the rest of the country.

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