Why Albino Animals Aren't Always White (And Non-Albino Animals Are)

Recently a rare white kiwi made it through a surgery. The doctors and scientists who treated it were quick to point out, it was not an albino kiwi. Instead it was a color morph, specifically one with leucism. Find out how things besides albinism can make you white, and why things don't have to be white to be albino.

City dwellers will have spent much of their time wading through flocks of pigeons. If they have looked down, instead of just stomping furiously, they will have noticed a lot of different coloration among the pigeons. Some will be patterned blue, and some almost black-gray, and some will be a rusty brown. Some, however, will be speckled with white, or almost pure white. Scientists used to call these birds - or other creatures like lizards and snakes that manifested white spots or speckles — cases of partial albinism.


It seems, though, that that is not the case. Ailbinism is caused by a mutated gene that stops all production of melanin, one of the primary biological coloring agents. Melanin colors skin, hair, feathers, scales, and eyes. Without this pigmentation, many animals have stark white bodies and red eyes, since the blood in the retinas make all eyes red without a layer of pigment to disguise it. Many animals, but not all of them. There are other pigments that are found to color biological specimens, the main ones being carotenoids. Albinism wipes out melanin, but not these other pigments, which is why orange-red pythons are called albino even though they aren't white.

Since albinism means that no melanin whatsoever is produced, there can't be any such thing as 'partial albinism.' Either melanin is produced or it isn't. What gives us all those speckled birds isn't the mutated gene causing albinism, it's the mutated gene causing leucism. Leucism causes the disruption of the flow of pigment to anywhere on an animal. This can cause only one pigment to be dumped, giving animal with the same markings as their fellows, but on a different color scale. It can cause pigments to be distributed to some places on the animal's body and not others, giving animals patches of white. It can also wipe out all pigment to all parts of the body. White lions and white peacocks are often referred to as albino animals, when in fact they're - slightly less quotable - leucistic animals.


So how to tell the difference? Anything that has a speckled or patched appearance is leucism. But while leucistic animals have different pigmentation on their bodies, they have regular pigmentation in their eyes. Albino animals alone will have red, deeply photosensitive eyes.

Top Image: Getty Images

Python Image: WWL

Lion Image: Stano Novak

Via BBC, Cornell and Web Exhibits.


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