A puppy who is biting you or someone else in the family is doing so because he has not yet learned the rules of playing with humans. Your puppy has not accepted his subordinate position in your family. He may be acting aggressively but, in fact, he is not considered an aggressive, dangerous dog. At this point, he is just an obnoxious pup who desperately needs to be trained. The first thing to realize is that a puppy will put everything and anything into his mouth. He expresses himself with his mouth. During teething time at age four to six months, he has a great need to mouth everything. There are ways to change this behavior. Please understand that your puppy is not bad if he is mouthing you quite vigorously.
If you administer any kind of physical punishment when he bites too hard, he will eventually respond in kind. He will learn to defend himself whenever anyone raises a hand to him and will become a dangerous adult dog. During teething time provide things for him to chew on. For example, soak old wash rags in water, ring them out, and put them in the freezer. Whenever he has a need to chew on you or the furniture, give him one of these wash rags to work over. Provide a box filled with chew toys such as nylon bones or hard rubber balls. A PUPPY MUST HAVE SOMETHINGS TO CHEW ON as there teeth hurt and it's part of development. It is best not to play games where your hand is near his mouth. If you do, however, train him not to bite when you are playing.
It is natural for a dog, at one time or another, to get into a fight with another dog. Some dogs are more prone to fighting than others. They either act, or are, more aggressive for a variety of reasons. Amazingly enough, most dog fights do not result in serious injury. It is not a good idea to try breaking up a dog fight because you might end up being the one who gets injured. Dogs act aggressively toward other dogs for a variety of reasons. A puppy who was not properly socialized to other dogs, i.e., allowed to play or romp with various kinds, sizes, and both sexes of dogs, will naturally grow up feeling anxious and tense in the company of other dogs. Some dogs are not social because of their need to defend territory. The territory might be the yard, the house, or personal territory such as the food bowl or the bed. There are hormonal aspects to aggression toward other dogs.
A female in heat, or with puppies, might act aggressively toward other dogs. Two unneutered males will be more aggressive toward each other than two neutered males. A dog who is tied up or restrained in some way acts more aggressively because he senses that he is defenseless. Some dogs act any way they want because they have assumed a leadership position with their caregiver. A dog may act aggressively because he has been attacked by another aggressive dog sometime in his life. A dog may act aggressively because he has learned this behavior from his mother or he may have inherited this characteristic from one of his parents. He may have been the runt of the litter, learning to fight for a feeding space. As you can see, there are many ways in which a dog acquires a disposition for acting aggressively toward other dogs. It is important for you not to unintentionally reinforce this kind of behavior. For example, if your dog growls at another, do not give him reassuring words like, "That's okay." Also, do not pick him up. If he growls or snaps at another dog, do not try to physically restrain or soothe him.
A dog will sense your uneasiness, and this is a signal to act even more aggressively to protect you! Do not think you are making a good watch dog by saying "Good Dog" when he growls at another dog. You are creating a mean dog. If your dog is acting aggressively toward other dogs, here are some things you can do. Take him for frequent walks where he can be exposed to other dogs. Do not restrain him for wanting to investigate another dog unless you know his intentions. Act and sound happy by laughing or singing, giving your dog the message that you are not concerned by the approach of another dog. Praise your dog for appropriate behavior, i.e., not growling, snapping, or pulling on the leash. Get control of your dog. Take a leadership position by training your dog in the commands of sit/stay and down/stay. If you have not already done so, get your dog neutered. This will reduce his territorial tendencies