Minnesota Zoo Media Contact

If you are a member of the press, please contact: Josh Le
Communications and Media Relations Manager
Minnesota Zoo
13000 Zoo Boulevard
Apple Valley, MN 55124
952.212.3428 direct
952.431.9300 fax
[email protected]

Apple Valley, MINN – October 7, 2016 – Four female bison at the Minnesota Zoo may give birth to calves fathered by bison in Yellowstone National Park this spring, following the successful transfer of embryos to the females earlier this fall, with researchers from Colorado State University (CSU) using a new breeding method with potential to expand the genetic diversity of bison herds in Minnesota and across the country. The four females are part of the Minnesota Bison Conservation Herd collaboratively managed by the Minnesota Zoo and the Minnesota Department of Natural Resources (DNR).

In September, the Minnesota Zoo partnered with Dr. Jennifer Barfield and others at CSU to transfer embryos into four bison cows at the Zoo using embryos generated from bison originating in Yellowstone National Park. These embryos were created using in-vitro fertilization in a lab at CSU and were frozen for storage. Dr. Barfield with the assistance of Dr. Greg Farrand, a large animal veterinarian from Colorado, successfully implanted them on-site at the Minnesota Zoo. An ultrasound will be conducted in the coming months to confirm if the animals became pregnant after the embryo transfers and that the pregnancies are on track for successful births next spring at the Zoo.

“I am very pleased with how smoothly the embryo transfers went,” said Colorado State University’s Dr. Jennifer Barfield. “While a new calf with valuable Yellowstone genetics would help augment the genetics of the Minnesota herd, it will also demonstrate that we can use reproductive technologies to move the Yellowstone genetics outside of the park without the threat of spreading the disease brucellosis, which has implications for bison conservation on a broader scale.”

“We are excited about this partnership with CSU and are very hopeful that this will work and we can finally add valuable Yellowstone bison genetics to our Minnesota Bison Conservation Herd,” says Minnesota Zoo’s Director of Animal Collections, Tony Fisher.

Yellowstone bison genetics are not well-represented in the Minnesota Bison Conservation Herd and are extremely desirable for increasing the herd’s genetic diversity. However, because of a transfer moratorium, obtaining a sexually mature bull to breed naturally has been impossible. The moratorium was established because bison in Yellowstone have a high probability of carrying a contagious bovine disease, known as brucellosis that causes spontaneous abortions in pregnant females. The frozen embryos from Yellowstone were carefully treated prior to the transfer to prevent any chance of transmitting this disease.

“Bison from Yellowstone National Park are some of the only American plains bison that have survived on their own in nature without humans guiding breeding,” added Molley Tranel Nelson, regional resource manager for Minnesota State Parks and Trails. “Free of cattle genes and selective breeding programs, they are one of the few bison herds where natural forces have continually shaped their genetics.  They are incredibly valuable to the diversity of the Minnesota Bison Conservation Herd.”

At one time, bison herds in North America were estimated to number between 30 and 60 million animals, and they roamed throughout all but the northeastern portion of Minnesota. During the late 19th century, bison were hunted to near extinction until fewer than 1,000 animals remained in the entire United States. The last wild bison observed in Minnesota was in Norman County in 1880.

During the remarkable comeback of North America’s largest land mammal, a silent genetic threat was introduced. Domestic cattle were allowed to interbreed with many of the protected herds, contaminating and changing the character of the American plains bison genome. It is estimated that less than one percent of the world’s remaining American plains bison have tested free of cattle genes. The DNR reintroduced bison into Blue Mounds State Park near Luverne, MN in 1961, and genetic testing from 2011-2013 found they were largely free of any genetic material that would have come from cross-breeding with cattle, making them rare.

In the fall of 2015, the Minnesota Zoo and DNR released eleven bison at Minneopa State Park, three females from the Zoo and eight females from Blue Mounds State Park to start a bison herd near Mankato. The Minnesota Zoo will continue to partner with the DNR to release more Zoo-born bison that have tested free of cattle genes into Blue Mounds State Park and Minneopa State Park in an effort to increase the Minnesota Bison Conservation Herd to 500 animals.

The Minnesota Zoo is a year-round destination located in Apple Valley, just minutes south of Mall of America. Its mission is to connect people, animals and the natural world to save wildlife. For more information, call 952.431.9500 or visit mnzoo.org. The Minnesota Zoo is an accredited member of the Association of Zoos and Aquariums (AZA) and an institutional member of the World Association of Zoos and Aquariums (WAZA).