YELLOWSTONE NATIONAL PARK — Yellowstone National Park (YNP) officials have confirmed that a white bison calf was born in Lamar Valley on Tuesday, June 4, which is a landmark event in the ecocultural recovery of the park’s bison herd, according to the National Park Service (NPS).
Yellowstone’s Center for Resources Bison Management Team reported that numerous photos of the calf were taken on June 4 from park visitors, professional wildlife watchers, commercial guides and researchers. Park biologists say that the calf is leucistic (black eyes and hooves with some pigmentation), rather than an albino animal.
“Leucism causes white coloration, white patches, spots or splotches on the skin or fur,” the NPS wrote on its website. “Leucism is also discernible from albinism because leucism does not affect the pigment cells in the eyes.”
According to the NPS, the white pigment is a natural genetic trait preserved in Yellowstone’s bison. The rare gene could have revealed itself due to wild bison populations successfully reaching 3,000 to 6,000 animals.
This marks the first report by the NPS of a white calf being born in YNP. According to YNP, the birth of a white bison calf in the wild is believed to occur in one in one million births or even less frequently. The white calf is considered a rare natural phenomenon that is known to have only occurred once before the near extinction of bison in the late 19th century, when bison numbered in the tens of millions.
The park’s bison population fluctuates from 3,000 to 6,000 animals in two subpopulations; the northern herd breeds in the Lamar Valley and the central herd breeds in Hayden Valley. The NPS estimates this year’s pre-calving bison population to be around 4,550 animals. The NPS will complete annual post-calving counts this August. Each spring, about one in five bison calves die shortly after birth due to natural hazards.
To date, there have been no confirmed sightings of the calf since June 4.
