Many people who have a Yorkie as a pet have two, because they often have separation anxiety when left alone and 'they don’t enjoy being alone.' The particolour coat is white with black-blue and tan. The white is caused by the recessive piebald gene. It is very rare to get a particolour, and if one is found, it tends to be very expensive. Like other small breeds, Yorkies are also prone to severe dental disease. Because they have a small jaw, their teeth can become crowded and may not fall out naturally.