Mouthiness in puppies, while natural, is an undesirable behavior. Puppies primarily use their mouths to explore their environment, as the sense of taste and touch in and around the mouth is among the first to develop. A mother dog typically teaches her puppies about biting - what is considered "too hard" and what is excessive. However, when we acquire puppies, we often do not have the benefit of this maternal guidance, so it becomes our responsibility to teach them appropriate behavior. While some level of mouthing for exploration is acceptable in puppies under 4 months old, repetitive or painful biting should be discouraged. Here are some tips for discouraging mouthy behavior.