Actually the act itself is not mating, but it is a direct act of Dominating. He's just trying establish his rank among your pack! It doesn't matter what age he is....no matter how cute these dogs are they are still male terriers not a stuffed toy. That is a typical normal male trait/action. They do it when they are excited and want to control the situation. Unless you plan on Breeding him? I suggest you get him nuetered as soon as your Vet. says it's OK.? Some males mature faster than others. Good Luck!
