This type of behavior is one that comes naturally to a puppy, as they use their mouths to explore the world, much in the way a baby uses its hands and eyes. It's important to recognize that nipping and mouthing is not a display of aggression, and is in fact nothing more than curious exploration.
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From the moment they are born, puppies use their mouths to acquaint themselves with their mother, den, and littermates. By the time they are a couple of weeks old, they move from exploration to play, using their mouth to gently nip and mouth their brothers and sisters. Some dogs carry the nipping behavior into adulthood, usually because they were removed from the litter too soon or have owners that don't mind a little bit of rough play.
Biting is actually important in the development of a puppy as it teaches them bite inhibition. This happens when they nip a little too hard causing another puppy in the litter to yelp in pain. Since play usually ends at that point, the puppy learns that there are unpleasant consequences to biting too hard.
The same works in reverse, when he is bitten too hard by another puppy and experiences that pain first hand. This is why many breeders won't allow a puppy to leave the litter until that behavior has been taken care of, knowing full well it can result in a 'maladjusted' puppy if he is allowed to leave too soon.
Even when a puppy has demonstrated that he has learned bit inhibition, he has to receive further training in his new home to reinforce that behavior. The fact is that humans feel the pain of a bite more quickly than a puppy, so the slightest sign of bite pressure is a behavior that has to be corrected.
A dog that hasn't learned bite inhibition can be annoying and dangerous, with the simplest play session often escalating into something more. A puppy has sharp teeth, but lacks the real jaw strength to do anything more than draw a little blood. Adult dogs can cause some real damage, though, which is why that behavior has to be nipped in the bud.
If you have a puppy or adult dog that is struggling to kick their nipping and biting behavior, there are some steps you can take to teach bite inhibition. Before getting started, it's worth noting that these tips will work with dogs of all ages, but these methods might take a little longer with an adult dog.
The bite behavior of a dog is often dependent on the owner. Some owners don't mind teeth touching their hands, as long as there is no pressure, whereas others want to teeth at all. This is particularly true of owners of large dogs where biting and nipping can quickly get out of hand.
If you want to teach your puppy that he has gone too far with a nip or a bite, be sure to give out a shrill squeal as though you are in real pain. Turn your body away from him completely as you do so, maybe even getting up and walking away, making sure not to make any sort of eye contact with him.
Completely ignore your dog during this period, as your goal is to make him feel socially isolated for about 20-30 seconds. Try not to extend it too far beyond that point as he may simply forget about you and turn his attention elsewhere. If any friends or family members are in the room during that time, make sure that they know to follow your actions.
It's basic human nature for dogs to want to chew on something, so if you'd rather the focus of their attention not be your hands and fingers, provide them with a suitable chew toy. The need to chew often comes when they play which, if you play along, can lead to nipping. Try to get him to focus on the toys or rawhide bones when he plays, but if he should turn his attention to your fingers or starts to snap, he needs to be given an adjustment.
You can correct him with a sharp "NO!!", or "AH-ah-aah" or some other warning that will get the message across. If those actions cause him to stop his unruly behavior, make sure to give him praise before directing his attention to a more appropriate chew toy. When he bites the toy, praise him again.
NEVER resort to physical punishment, under any circumstance whatsoever. That sort of punishment is never a good idea and often leads to more bad behavior from your dog. It's much more effective to use a humane technique to show your displeasure, with the cold shoulder method outlined above being one of the most effective.
Dogs love to make their human friends happy, but he needs to know what the guidelines are. As soon as he learns the laws of the home, he will have a much better chance of being a good dog and behaving properly. The 20-30 second timeout gives him time to cool down when he is excited. If he continues nipping and biting after his timeout, you might consider crating him and leaving him there for 5 minutes or so.
When you feel that he has calmed down, you can bring him out of his crate and start playing again. This time around, try to bring the excitement level down to see if he plays better when he is not quite so excited. Dogs that are prone to excitement without much prompting might be better suited to non-contact playtime.
For example, if you own a border collie, you might consider Frisbee and fetch games when it comes time to have some fun. Tug-of-war is another fun game that you can play together, but try to instill a 'drop it' command so that he knows when to quit. If you choose games that involve any sort of contact, no matter how mild, you are literally encouraging him to channel his wild side and use his mouth. Keep the games low-key and they will always remain friendly.
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