Welcome to YT. I have never heard of a vet stating a male yorkie shows no signs of needing to be neutered. Neutering a puppy is the responsible thing to do to prevent unwanted pregnancies and to prevent cancer later in life. I would definitely check with the vet to see what is going on with your female.
__________________ Karen  Kacee  Muffin 1991-2005 Rest in Peace My Little Angel |