I've seen a lot of albino squirrels in Columbus, Ohio.  Some of the colored deer come from having a species of onchocerca that dwelt in the deer herd when it was larger, move first to the cows in order to survive, and now back to the larger deer herd.  They bring a little cow DNA along with them.  Herefords, holsteins, black angus & jersey colors.  I've seen pictures of one looks like it's part  Little Joe Cartwright's horse!