A piebald is an animal, such as a horse or ball python, that has a spotting pattern of large unpigmented (sometimes expressed as white) areas and normally pigmented patches (black in the horse pictured). The colour of the animal's skin underneath its coat is both the natural color (under the black patches of hair in this example) and pigmentless (under the white patches in the horse example). This alternating colour pattern is irregular and asymmetrical. Other than colour, it is similar in appearance to the skewbald pattern. Some animals also exhibit colouration of the irises of the eye that match the surrounding skin (blue eyes for pink skin, brown for dark). The underlying genetic cause is related to a condition known as leucism.
In British English piebald (black and white) and skewbald (white and any colour other than black) are together known as coloured. In North American English, the term for all large spotted colouring is pinto, with the specialized term "paint" referring specifically to a breed of horse with American Quarter Horse or Thoroughbred bloodlines in addition to being spotted, whereas pinto refers to a spotted horse of any breed. In American usage, horse enthusiasts usually do not use the term "piebald," but rather describe the colour shade of a pinto literally with terms such as "black and white" for a piebald, "brown and white," or "bay and white," for skewbalds, or color-specific modifers such as "bay pinto", "sorrel pinto," "buckskin pinto," and such.
Genetically, a piebald horse begins with a black base coat colour, and then the horse also has an allele for one of three basic spotting patterns overlaying the base colour. The most common coloured spotting pattern is called tobiano, and is a dominant gene. Tobiano creates spots that are large and rounded, usually with a somewhat vertical orientation, with white that usually crosses the back of the horse, white on the legs, with the head mostly dark. Three less common spotting genes are the frame and splash overo genes, that creates a mostly dark, jagged spotting with a horizontal orientation, white on the head, but dark or minimally marked legs. The sabino pattern can be very minimal, usually adding white that runs up the legs onto the belly or flanks, with "lacy" or roaning at the edge of the white, plus white on the head that either extends past the eye, over the chin, or both. The genetics of overo and sabino are not yet fully understood, but they can appear in the offspring of two solid-coloured parents, whereas a tobiano must always have at least one tobiano parent.
Piebald in other animals
Dogs, birds, cats, pigs, dairy cattle and many other animal species may also be "pied" or piebald. Snakes, especially Ball Pythons, may also exhibit seemingly varying patches of completely pigmentless scales along with patches of pigmented scales. The term was used in The Conservationist by Nadine Gordimer when referring to kingfishers. The various types of magpie are so called because of their pied plumage.
The bald eagle derived its name from the word "piebald", in reference to its white head and tail contrasting with its dark body.
- "Introduction to Coat Color Genetics" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008