Sometimes a Yorkshire terrier is so small that it can fit inside of a drinking cup and these popular little dogs are a fun addition to any home. But sometimes a family will already own a small animal like a hamster or a guinea pig and while it's fun to own many animals, these small pets should be kept away from teacup Yorkies because as a type of ratter it's possible their most basic instincts will kick in and tell them that a tiny gerbil needs to be eliminated. As long as small rodent type animals are carefully caged there should be not dangerous interaction.