Fuzzball or future terror?

Every once in a while, you’ll come across someone proclaiming that a breed of dog (usually a large one) will grow up to “turn” on its owners. We guess this means a dog whose behavior was “just fine” as a puppy starts growling at or biting its handler once it’s an adult. Is this a real thing? Are German Shepherd puppies likely to attack their owners once they become adult dogs?

Where this idea comes from

It’s hard to say exactly how this notion started, but the truth is that a young puppy that bites or otherwise acts aggressively is unlikely to cause much damage to an adult human, unless the pup’s teeth hit a nerve or an eyeball. On the other hand, a fully grown dog of any breed who bites hard enough to break skin will do more damage, because it has adult teeth and stronger jaws.

Are all puppies “good”?

Another reason for the popularity of this idea is that many people think all puppies are playful and sociable, or that puppies who behave aggressively are “just playing.” The truth is that dogs of all ages display the full range of canine body language, including stress signals and bite warnings, and these are often only noticed by people who are trained to see them. Most pet owners are unaware of these subtle signs, leading to claims that the dog “bit out of nowhere,” when in fact the pup may have been displaying warning signs for months and months leading up to the bite.

Do German Shepherds’ personalities change as they get older?

As dogs mature, especially dogs who have not been spayed or neutered, they develop less tolerance for things that might not have upset them as younger pups. Unaltered dogs also have hormonal surges that can affect their excitement levels. (More excitement = more likely to aggress.) So while the dog’s overall personality likely stays the same, its tolerance for other dogs and for events that might not have bothered it as a puppy goes down. This often translates into a German Shepherd who dislikes other dogs starting around 2 to 3 years old. It sometimes means extra sensitivity to strangers starting at around 2 years old, as well.

A scary or unwanted experience during the puppy’s sensitive periods (9-12 weeks and again at 6-12 months for German Shepherds) can permanently alter the puppy’s personality, at least under those circumstances. We once had an otherwise-friendly-with-everyone male German Shepherd who was traumatized by a veterinarian at 8 months of age. He barked, lunged and growled at that veterinarian every visit thereafter, to the point that we ended up switching vets. Even then, it took years of training and behavior modification for him to quietly accept an examination from the new vet.

Bite inhibition

A German Shepherd puppy who was never taught proper bite inhibition can grow up to do real damage. Bite inhibition means a puppy learns to use its mouth gently. This process is taught to the puppy starting with the mother and litter mates until 8 weeks or so of age — which is why you should never remove a puppy from its mother and litter mates before 7 weeks. The process continues with the puppy’s new handler until the age of 4-5 months. If you don’t know how to teach bite inhibition, you can find numerous examples on YouTube.

Resource guarding

One common cause of dogs biting or acting aggressively towards their owners is resource guarding, which means the dog growls or bites if someone comes near or tries to take the dog’s food or toys, or tries to remove the dog from a resting place. This trait can often be seen even in young puppies, and is sometimes made worse by people taking the puppy’s food or toys in an attempt to “train” him not to guard. Thankfully, prevention in puppies is possible. If you have a German Shepherd who resource guards, it is imperative that you seek help from a qualified behavior professional right away. (See APDT.com or IAABC.org to search for help.)


Medical reasons for aggression, especially aggressive behavior that seems to start abruptly, are not uncommon. Brain tumors or other neurological problems, chronic diseases or severe pain can cause all dogs, not just German Shepherds, to act in ways they otherwise never would. We once had a client whose normally friendly, loving dog (not a GSD) bit her arm repeatedly and broke skin through her heavy winter coat — because he was in extreme pain. Once he had surgery to repair the medical problem and had recovered, he became his friendly, loving self again.


Probably the most obvious reason, but thankfully rare, that an adult dog might decide to aggress towards its handler is abuse. While most German Shepherd owners never knowingly hit or hurt their dogs, harsh training methods can also bring out aggressive behavior. A study of training methods showed that “confrontational methods applied by dog owners… were associated with aggressive responses in many cases.” (Herron, et al)

It’s also worth mentioning that many, many dogs who are physically abused never bite anyone. But few people would blame a dog whose tolerance for abuse came to an end in the form of aggressive behavior.

Will my German Shepherd become aggressive?

The only guarantee we have is that ANY dog can bite. However, being an educated German Shepherd owner who learns about dog body language, who works to socialize and train your dog using positive training methods, and who keeps your dog out of situations he or she hasn’t learned to handle emotionally can significantly decrease that risk.

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Herron, Meghan E.; Shofer, Frances S.; Reisner, Ilana R. Survey of the use and outcome of confrontational and non-confrontational training methods in client-owned dogs showing undesired behaviors. Applied Animal Behaviour Science vol. 117 issue 1-2 February, 2009. p. 47-54

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