Rare white bison calf born in Wyoming state park draws flocks of visitors

Officials at a Wyoming state park thought the bison birthing season was finished, until a rare surprise showed up that’s drawing flocks of visitors to the area.

Earlier this month, staffers at Bear River State Park in Evanston found a “little white ball of fluff” among the four reddish-brown colored bison calves − the first white calf born in the park’s 32-year history, according to a statement.

Wyoming Hope, the park’s 3-year-old white heifer, had given birth on May 16 to a white calf − an extremely uncommon phenomenon, according to Bear River officials. Because the mother is white, “it isn’t unusual that the calf is white too,” the park added.

The National Park Service said white bison are considered sacred to many Native American tribes, including the Sioux, Cherokee, Navaho, Lakota, and Dakota. Blair Gopher, a member of the Blackfeet and Ojibwe tribes told the Great Falls Tribune, part of USA TODAY Network, that white buffalo is symbolic of a message from the Creator, or Great Spirit.

"Since people have started breeding bison, in the last 20 years or so, more white calves have been born. The whiteness is a recessive gene, but it's important to know that some of them don't retain their whiteness as adults," Craig Knowles, a wildlife biologist who's worked with buffaloes for over two decades, told the outlet.

Knowles added that white buffalo can be lucrative for private ranchers, as some people will pay large sums to selectively breed a white bull and white cow.

What causes white fur in these animals?

White fur in bison can be caused by albinism (the absence of any pigmentation or coloration resulting from a melanin deficiency), leucism (an abnormal condition that produces white fur with blue eyes, instead of pink seen in albinos), or more commonly, a genetic makeup born from bison-cattle crossbreeding that makes white fur more common.

How rare are white bison?

The National Bison Association has estimated white bison births occur at a frequency as rare as 1 in 10 million, though they have become more frequent in recent years, the Great Falls Tribune reported.

National Bison Association executive director Jim Matheson said an exact statistic is hard to pin down, Native News Online reported.

“The bottom line is: we just don’t know,” Matheson told the outlet. “Those records were never kept, so it’s kind of hard to put a number on it.”

Almost all bison today show at least trace amounts of cow genetics because of purposeful or accidental cross breeding when bison populations plummeted in the 1800s. However, “a white bison birth is still fairly rare,” Tyfani Sager, the park’s superintendent, told Cowboy State Daily.

In 1994, what was believed to be first white calf since 1933 was born on a farm in Janesville, Wisconsin, according to the National Park Service.

In this instance, the 30-pound calf’s distinct coloring is likely the result of Charolais cattle and bison crossbreeding.

This article originally appeared on USA TODAY: Rare white bison calf born in Wyoming at Bear River State Park