Leucism (a.k.a. achromia) is a state of reduced pigmentation that can occur in individuals of almost all species of animals. The animals skin may appear pink, its fur anywhere from beige to blond to pure white. However leucistic animals have normally colored eyes. Leucsm is produce by the expression of a single recessive gene. Partial expression of leucism can lead to an animal having a pied or spotted appearance. By contrast albinism if a complete lack of pigmentation.
Overall leucism tends to be a disadvantage to an animal. They lose the function advantages of coat marking such as camouflage. Leucistic zebra finch chicks lack the 'gape marking' that encourages the parents to feed them, leading the parents to favr normally colored chick when food sources are limited.
This young hippo was photographed on the banks of the Mara River in 2010.
White lions are described being first sighted variously in 1928 or the 1940s. They are popular exhibits in zoos. Some groups are advocating protection of white lions in the wild, but they are not recognized as a species and so cannot be given most designations of protection separate from other color morphs.
White lion cubs have been reported in a number of African wildlife reserves, but they rarely survive into adulthood. This may be because their pale color makes them less effective hunters (Turner et al 2015).
White tigers (who retain their black stripes) are not a separate species, but another case of leucistic coloring.
In birds leucism is defined as a lack (or partial lack) of eumelanin and phaomelanin in the feathers, although the soft tissues are often at least partially pigmented.
A number of the barnacle geese of the Solway Firth (United Kingdom) display leucanism.
This Adele penguin (see right, native of Antartica, sighted 2008) is one of many penguins from a range of species that display leucism.
This leucistic sandhill crane was photographed in 2008 at Ewing Bottoms, Indiana.
Other examples of leucistic birds include:
- American Robin (Ontario, 2007)
- Blue tit
- Prairie Chicken (2012)--Particularly striking with its distinct orange markings.
- Puffin (UK, 2010)
- Ruby-throated hummingbird
Leucistic animals retain pigment to different degrees. Partial leucism can lead to specific areas of the body being white and others retain full normall coloration such as with the crow shown right, or this squirrel who is whie colored only on the tail.
- Turner, J. A., Vasicek, C. A., & Somers, M. J. (2015). Effects of a colour variant on hunting ability: the white lion in South Africa. Open Science Repository Biology, (open-access), e45011830.
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- van Grouw H (2006). Not every white bird is an albino: sense and nonsense about colour aberrations in birds. Dutch Birding [pdf]