With their massive heads, distinctive humped back and powerful builds, Yellowstone National Park’s bison may look similar, yet it is something much smaller that makes them unlike most other bison in North America.
At a molecular level, Yellowstone’s bison contain 75 percent of the genetic diversity of the entire species; they are the only publicly managed animals that are free of any cattle genes; and they can trace their heritage back hundreds of years to a time before the arrival of Europeans in the Americas.
For these reasons, Jim Derr, a professor in the Veterinary Pathobiology Department at Texas A&M College of Veterinary Medicine and Biomedical Sciences, said, “The bison in Yellowstone National Park are pivotal to the long-term conservation of the species.”
Derr spoke at a recent gathering of a panel in Washington, D.C., that was formed by the National Academy of Sciences. The group is charged with updating a 1998 study on the prevalence and spread of brucellosis in the bison and elk of Yellowstone National Park.
Derr’s talk and the panel’s meeting come on the heels of the National Park Service and state of Montana agreeing last year to work on a new bison conservation plan.
Montana representatives have previously said the state would like park officials to reduce the bison herd to 3,500 animals. This summer the herd numbered 4,900. Only if the population is reduced is Montana willing to give bison more room to roam outside the park in areas like national forest lands near West Yellowstone.
Killing any of the Yellowstone bison, except through tribal hunting, has long been controversial. And attempts to cull bison and move them to conservation herds has run into difficulties. Members of an interagency group of federal, state and tribal partners have been negotiating this fall on whether and how many bison should be culled from the park population this winter as they migrate into the Gardiner Basin north of the park.
Since the 1980s, more than 6,300 bison have been slaughtered and almost 1,900 killed by hunters. The park retreated from an original proposal to kill 1,000 bison this winter with a final determination on how to proceed yet to be announced.
Derr and his associates’ research points to the danger of large reductions, and even to reductions of animals that test positive for the disease brucellosis. Without looking at the culled bison’s genetics, it’s unknown what harm the process could have on “one of the major genetic foundation populations for this species,” he said. Under questioning he said it would be possible to test captured bison’s genetics before slaughtering them or removing them from the herd as a means to preserve a diverse genetic pool.
Several factors make Yellowstone’s bison so unusual. One is that 22 animals survived the slaughter of the Plains bison in the 1800s, a remnant herd that hid in the remote region. To that, in 1902, 18 bison were added from Western Montana, a population that colonized the National Bison Range in Moiese. Three bulls also were brought to the conservation herd from Texas.
Genetic analysis that compared the Yellowstone bison to one killed in the park’s Hayden Valley in 1856 by its namesake, geologist Ferdinand Hayden, revealed the present bison are related to the one Hayden killed. That bull is stored in the Smithsonian’s collection.
Work published three years ago showed two distinct bison herds in Yellowstone. Although they intermingle during the summer, for the most part they separate to breed.
“These two herds are as dissimilar as either herd is to the Wind Cave bison,” Derr said, referring to the herd at the South Dakota national park.
Past attempts to reduce the prevalence of brucellosis in Yellowstone bison by removing those that test positive for exposure to the disease is not smart, Derr contended, as had one of his former Texas A&M colleagues, Joe Templeton.
Derr said such removals were dangerous because they tended to target family groups and said it would be similar to going to a “Smith family reunion” and killing all those in attendance.
“The point Dr. Templeton made is we don’t know what that does to a population,” Derr said.
So any management decisions need to take into account that Yellowstone’s bison are unlike any others, and that there are two distinct herds within the park.
“The fact of the matter is that Yellowstone is a special bison herd from a genetic standpoint and in other ways,” Derr said.