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Cause
Piebald coloring is caused by genetics. Animals start with the genes for a black base coat. The white markings are due to the presence one or more recessive piebald alleles that causes spotting or totally white coats. In some animals, such as dogs and cats, white fur often is accompanied by deafness in either one or both ears.
Deafness
Research has been done on deafness and the presence of piebald genes in mice and some dogs, such as dalmatians and border collies, that carry piebald genes. One study titled "The Dalmation Dillema; White Coat Colour and Deafness" published in 1999 in the "Journal of Small Animal Practice" offers evidence that pigment cells may help in the development of small hairs in the inner ear called cilia. When piebald genes are present, some animals experience a lack of pigment covering their ears. It is thought that the cilia are not supported and then die, resulting in deafness.
Piebald Horses
There are three types of spotting alleles that cause the three basic types of piebald horses. The tobiano is a dominant gene that results in large, rounded areas of the animal's coat that otherwise would appear dark but are overridden by the gene so that they no longer have any pigment. Commonly these animals have white legs and black heads. Overo genes create dark, horizontal spots, with white on the head. Sabino patterning has the least amount of white, with white on the legs and belly, sometimes extending to the head.
Other Animals
Dairy cattle, pigs and many other animals such as the ball python also exhibit piebald patterns. Some animals were named because of their black and white coloring. Magpies were named after the term piebald; the bald eagle also derived its name from the term due to the contrast between its pigmented body and white head -- enough though it is not a true piebald.