The Greater Yellowstone Area is the last known reservoir of Brucella abortus bacteria, believed to have been introduced to the park's bison by
domestic cattle at the beginning of the 20th century. Roughly half the bison population in Yellowstone tests positive for exposure to the disease,
which is primarily transmitted by contaminated birthing materials deposited on grazing grounds. Brucellosis also poses a threat to neighboring cattle
herds when infected animals wander over the park's invisible boundaries. Researchers from the USDA's Animal and Plant Health Inspection Service (APHIS)
are interested in whether temporary sterilization with GonaCon can prevent the shedding of bacteria-riddled afterbirth and help block disease
The USDA has spent close to two billion dollars over nearly eight decades trying to stamp out the disease, which carries hulking environmental and financial consequences. Bison who leave the park to seek food at lower elevations are
routinely rounded up and quarantined, and those found to have the disease are slaughtered. When brucellosis crops up on cattle ranches, herds must be quarantined and infected members butchered. Additionally, the bacteria can pass to humans through unpasteurized milk. Jack Rhyan, a veterinarian
medical officer and wildlife pathologist with APHIS, and the study's principal investigator, said that the focus on brucellosis is driven in part by
its implications for public safety. "Animal health is directly related to human health," he said.
But while the GonaCon study is still in the nascent stages, some conservationists are already voicing concerns. Stephany Seay, media coordinator of Buffalo
Field Campaign, a group that advocates for protection of the Yellowstone herd, views the USDA study as an experiment in population control.
"Brucellosis is being used as a tool to manipulate the movement of wild bison," she told me. According to Seay, GonaCon is a means of catering to ranchers
who don't want to compete with bison for grassland. "This is a centuries-old range war," she continued.
Indeed, the interests of land-users have historically clashed with bison and their habitat. Once scattered over the Great Plains, the American bison
population was demolished in the late 1800s by settlers hungry for meat, hides, and room for westward expansion. Numbers dwindled from an estimated 30
million to fewer than one thousand. By the turn of the century, Yellowstone held the nation's only remaining wild population of plains bison.
Biologists have determined in recent years that the herd is one of the last to retain genetic purity, with no traces of interbreeding with cattle.
From Seay's perspective, the significance of the Yellowstone herd is reason to encourage tolerance over further tampering. She and the Buffalo Field
Campaign have fought to expand range rights for bison. "The dispersal of wildlife lessens the prevalence of disease," she said. "By allowing bison to
roam, you're thereby also reducing risks." Ranchers anxious about contagion, she suggested, could immunize their animals against brucellosis rather
than meddle with neighboring wildlife.