In the third week with a puppy, many people's forearms look as if they had wrestled a cat. The puppy jumps, snaps, hangs on to your trousers, nips at your calf and thinks it is all brilliant. That is not a sign of an aggressive dog. It is a puppy exploring the world with its mouth that does not yet know how hard is too hard. That is exactly what it is learning now, in the weeks when it plays the most with littermates, other dogs and you.
The window of time, and which part of it is an estimate
In dog training, the window is usually given as roughly the eighth to the eighteenth week of life. That figure is a rule of thumb from practice, not a study result: there is no research that defines the period cleanly. What is well established is the general picture: the first months of life are the phase in which a dog learns social behaviour most easily. In practical terms: the earlier you start, the less effort it takes. And the longer you wait, the more.
Why bite inhibition is still the most important lesson
The assumption behind it is this: an adult dog that learned as a puppy how much pressure human skin can take will only nip, rather than bite, even when startled. At the vet, when a child steps on its paw, when it is in pain. To be honest: this assumption comes from training practice and is not scientifically proven, because for obvious reasons it cannot be tested. It is still the best available reason to invest time in these weeks: the cost is low, the possible gain is big. That is why good dog trainers teach puppy owners bite inhibition first, and everything else after.
What happens in the litter and what you take over
With its littermates, the puppy learns: if you bite too hard, nobody plays with you any more. The sibling yelps and walks away. The game is over. You take over exactly this principle. No more, no less.
The method that works
Step 1: The signal
When it bites too hard, you say a short, high "Ow", just as a littermate would yelp. At the same time your hand goes soft and still. No jerky movement, as that invites the puppy to chase. Some puppies do find the high yelp funny, though, and carry on. If yours is one of them, use a calm, low word instead and keep the rest of the method the same.
Step 2: The game ends
You stand up, turn away, fold your arms and are boring for ten to twenty seconds. If it keeps hanging on to your legs, you leave the room, door closed, again for ten to twenty seconds. Then you come back and carry on as if nothing had happened. Longer than twenty seconds does not help: otherwise the link between the bite and the end of the game is lost.
Step 3: The alternative
A puppy has to chew and bite, that is a need, not a fault. So you offer it something it is allowed to bite: a tug rope, a chew bone, a tug toy. The rule: teeth on skin ends the game, teeth on the toy makes the game more exciting. It learns the difference in one to two weeks.
Step 4: The dosage
At first you only react to really hard biting. When that becomes rarer, you react to medium nipping. Then to light nipping. After four to six weeks it should only touch skin with its mouth, without pressure. That is the goal: not "never a mouth on a hand", but "a mouth on a hand without hurting".
The mistakes that make everything worse
- Muzzle grabs, scruff shaking, rolling the puppy onto its back. These methods from old books create fear, not bite inhibition. A puppy that is afraid of your hand will later bite out of fear.
- Playing with your hands. If you roughhouse with the puppy using your hand, you teach it that hands are prey. Always keep a toy in between.
- Pulling away and flapping. A twitching hand is a prey animal. Going still works better than fleeing.
- Inconsistency in the family. If Dad finds the nipping funny and Mum forbids it, the puppy learns nothing except confusion. One rule for everyone.
- Ignoring tiredness. Most biting attacks come in the evening, when the puppy is overtired and wound up. That is not a training problem but a sleep problem. Puppies need 18 to 20 hours of sleep. Off to the crate or onto the blanket, quiet time.
Children and puppy
Children squeal, run and wave their arms about, so for a puppy they are the perfect prey game. Rule: children only play with the puppy with a toy in their hand and only when an adult is there. If the puppy nips, the child becomes a statue: fold your arms, stay where you are, do not scream. You practise this beforehand without the dog.
When it is not normal
If a puppy growls and goes stiff while doing so, if it snaps when you touch its food or toys, if it still bites hard at six months, or if you are afraid of it: get a trainer who works with positive reinforcement. The earlier, the easier. There is no shame in that, it is what most good dog owners do at some point.
Some comfort
The piranha phase passes. With the change of teeth from the fourth month it gets better, and by six months it is usually over. What remains is a dog that knows how careful it has to be with you. And a few scars on your forearms that you will show off proudly in two years.
The scars will fade, and so will the face from these weeks. A photo from the piranha days will still hang on canvas in your hallway in ten years, and you can see how it will look beforehand in the preview.
The complete starter pack, free of charge
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If you want to follow the topic beyond puppyhood, right into adolescence, that is exactly what Welpenerziehung & Junghundtraining (Puppy Training & Young Dog Training) is about.
Keep reading
- The first 30 days with a puppy: the plan for the whole first month
- Puppy training: the 5 rules: the basics behind it
- House training a puppy: the other big topic of these weeks
Source for the signal and the length of the break: ASPCA, Mouthing, Nipping and Play Biting. Accessed on 19.09.2026. The statements on the learning window and on the effect of bite inhibition in an emergency are rules of thumb from dog training, not study results.
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