What could make a baby bison white?
WASHINGTON — Photos of one white bison calf in Yellowstone National Park have raised both excitement and questions: How does that happen?
A park visitor said she took the photos in the park earlier this month, which showed a fluffy white baby boy being snuggled by his brunette mother. Park officials said this week that they had not yet seen a white calf in the vast park in Wyoming and Montana, home to about 5,000 bison, also called American buffalo.
In the wild, there are two genetic variations that can result in unusually light-colored animals: leucism and albinism. In both conditions, the animal inherits two copies of the gene mutation: one from each parent, which itself usually appears normally colored.
Leucistic animals lack some cells that otherwise produce melanin, a natural pigment that gives color to fur, eyes, feathers and skin. Their bodies may appear almost entirely white, or just a few white spots, and they generally have normal or dark-colored eyes.
Albinism, which is rarer, results from the complete absence of melanin. Albino animals are almost completely white and may have pale pink or orange eyes and impaired vision. Albino bison won’t have dark colors in their eyes, noses and hooves, says James Derr, a geneticist at Texas A.&M University.
The Yellowstone calf, with its black nose and eyes, is not albino, said Jim Matheson, executive director of the National Bison Association.
There is a third possibility: a light-colored calf could be the result of a bison crossed with a white domestic cow. In that case, the calf may be light brown in color, with brown eyes and a black or brown nose, Derr said.
Matheson said it is unclear how often white bison calves are born in the wild.
“We just don’t know how often it happens because we’ve never tracked it in history,” he said.
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AP reporter Amy Beth Hanson in Helena, Montana, contributed to this report. ___
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