WASHINGTON — Photos of a white bison calf in Yellowstone National Park have generated excitement as well as questions: How does that happen?
A park visitor said she took the photographs in the park earlier this month, showing a fuzzy white youngster being nuzzled by its dark brown mother. Park officials said this week that they hadn’t yet spotted a white calf in the sprawling park in Wyoming and Montana, home to about 5,000 bison, also called American buffalo.
In the wild, there are two genetic variations that may 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, who usually appear normally colored themselves.
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 only white in patches, and they generally have normal or dark-colored eyes.