A piebald or pied animal is one that has a spotting pattern of large unpigmented, usually white, areas of hair, feathers, or scales and normally pigmented patches, generally black. The colour of the animal's skin underneath its coat is also pigmented under the dark patches and unpigmented under the white patches. This alternating colour pattern is irregular and asymmetrical. Animals with this pattern may include horses, dogs, birds, cats, pigs, and cattle, as well as snakes such as the ball python. 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.