http://www.theithacajournal.com/news/stories/20021129/localsports/470126.html
While it may well be a once-in-a-lifetime happening for a hunter, it's not all that uncommon in the wild or in the Southern Tier. The term is "piebald" deer and it is the result of a genetic trait that occurs once in every 3,000-4,000 adults. The incidence rate increases if the deer is allowed to breed, increasing the piebald gene presence in the gene pool.
Wildlife biologists tell me that the gene(s) producing this abnormality not only increases the amount of white on the animal but quite often cause other features such as dorsal bowing of the nose, short legs, curving or arching of the spine, short mandibles and malformation of internal organs.
Many do not survive to adulthood and of those that do a good number look like goats. Some, however, remain quite normal and develop good racks.