People are excited about photos of a white bison calf in Yellowstone National Park. In fact, many of them are wondering how a white bison would even be able to exist in the first place.
A park visitor said she took pictures of a fuzzy white calf with its dark brown mother earlier this month. Park officials haven’t seen the white calf yet. Yellowstone is home to about 5,000 bison, also called American buffalo.
In nature, there are two genetic reasons why an animal might be unusually light-colored: leucism and albinism. For either of these to happen, the animal must get a specific gene change from both its parents, even though the parents usually look normal.
Leucistic animals don’t have some of the cells that make melanin, which gives color to fur, eyes, feathers, and skin. These animals might be all white or have white patches. They usually have normal or dark-colored eyes.
Albinism is less common and happens when there’s no melanin at all. Albino animals are almost completely white and often have light pink or orange eyes. They also tend to have poor eyesight. Albino bison would have light-colored eyes, noses, and hooves.
The Yellowstone calf isn’t albino because it has a black nose and eyes, according to Jim Matheson from the National Bison Association.
There’s a third possibility: the calf could be part domestic cow. In this case, it might be light tan with brown eyes and a black or brown nose.
No one knows how often white bison calves are born in the wild because no one has kept track of this throughout history.