A bison calf born in June in New York’s Bronx Zoo — the first genetically pure bison calf ever produced by embryo transfer — has Yellowstone genes.
The zoo waited until Thursday to announce the calf’s June birth to make sure that the calf, its mother and the 16-member herd of all-female bison got along, said Pat Thomas, general curator at the zoo.
“Our hope is to establish a herd of genetically pure animals and make them available for restoration programs,” Thomas said.
He foresees a herd of offspring of 10 to 15 individuals. “We’ll use those as a nucleus for a breeding herd and then use naturally bred animals to increase the herd size.
“How long it will take to achieve that, we don’t know, but that would be our goal,” Thomas said.
Although “it’s a bit premature to identify sites,” he said that the program could eventually help restore bison to the Montana landscape as well as spread the Yellowstone bison’s wild genetics to diversify other captive herds in zoos.
It will take several years to build up the herd because the bison offspring will need to mature and have offspring of their own. Bison cows don’t breed until age 3.
For now, though, the embryo transplant process will be repeated. Embryos have already been collected for another round of implantation and more will be gathered this fall.
Jennifer Barfield, a Colorado State University reproductive physiologist, oversaw the embryo collection and implantation into surrogate bison. The embryos are gathered by flushing the uterus of an ovulating bison cow with fluids before the eggs become attached. The fluids are then extracted and the embryo filtered out. Some of the bison were given drugs to produce more than one egg. The embryo-collection process takes about a half-hour.
Barfield said she sees the work as a new tool to implant disease-free Yellowstone bison genetics into new herds. Her methods may also provide a way to breed brucellosis out of the animals.
“This could be a very powerful tool in that task,” she said.
Brucellosis is prevalent in about half of the Yellowstone herd and can cause pregnant cattle to abort. Fear of the spread of the disease to cattle is one of the main points of controversy in management of Yellowstone bison that wander outside of the park’s boundary.
Thomas said he was initially uncertain whether the embryo transfer would work, although he was confident in the capability of his partners.
“I was optimistic that we would have success, but there is always a level of uncertainty,” he added. “I’m pleasantly surprised and glad that it worked.”
The breeding herd is kept out of public view, although another herd of 11 animals is in the zoo’s North American section, where visitors can see them. The Bronx Zoo, managed by the Wildlife Conservation Society, is the largest urban zoo in the United States. Although the zoo has a lot of “large charismatic species,” Thomas said the bison are popular because few people have seen them. “In many ways, they are as much of a national symbol as the bald eagle is,” he said.
The Bronx Zoo bison calf’s lineage is a testament to the interconnectedness of bison conservation in North America.
The embryo was taken from a Yellowstone bison cow being held in quarantine near Gardiner. Yellowstone National Park’s bison are considered the most genetically pure, free from inbreeding with domestic cattle.
The embryo was implanted into a bison cow that was donated to the zoo by northeastern Montana’s American Prairie Reserve. The reserve is establishing a herd of free-roaming bison on its private lands and public leased lands.
The reserve’s bison cow was a descendant of bison from Wind Cave National Park in South Dakota. That herd, established in 1913, was started with bison shipped from New York City, including the Bronx Zoo.
The director of the Bronx Zoo at the time was William T. Hornaday, a onetime taxidermist who in 1886 oversaw an expedition that killed 25 of the last remaining wild bison in Montana on the Musselshell River in order to preserve the vanishing species for museum display.
Only a year later, Hornaday had a change of heart and was calling for the preservation of the species by the Smithsonian Institute, including greater protection of the Yellowstone National Park remnant herd – only about 25 animals by then.
The fact that bison descended from the Wind Cave herd, which initially came from New York, are being used at the Bronx Zoo to breed the new genetically pure bison seems appropriate to the zoo’s general curator, Pat Thomas.
“It’s like the story has come full circle,” he said.