Locally Columbian Blacktail deer featuring piebaldry are common. There's a theory amongst the local dairy farmers that Holstein cattle have affected deer genetics, and produced the piebald deer.

I'm not ruling that out, but neither do I subscribe. Hybridism is far more common that we expect, as you can discover by visiting macroevolution.net, from the author of 'The Handbook of Avian Hybrids', the bible of the field. The speciation revealed in the fossil record far more strongly supports hybridization than Darwinian mechanisms, and this has been a stumbling block to evolutionary biologists for decades.

DNA studies of piebald deer are overdue.

Thanks!