How Come My Puppy Is Aggressive Towards My Older Dog?

Make sure your dog can escape the puppy at will to avoid fights.
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For puppies, play fighting is as natural as eating and sleeping. When you bring a new pup home, there's a good chance he'll occasionally engage your other dogs in mock brawls. True aggression is very different from play fighting, so watch for signs of hostility from the new arrival.

Play Fighting

Puppies use their teeth, paws and bodies during play fights with their siblings, mother and other dogs. There's no hostile intention, although mock fights can end up causing minor injuries. Young dogs should play fight for the first few months of their lives so they can learn boundaries during social interactions with other dogs. Pups learn how to control the strength of their bites during these play fights, so don't discourage them from doing it until they are about 4 months old, according to Georgia SPCA. Normally the victim of a bite during a play fight will yelp or yield by rolling over. This disruption trains the aggressor not to bite so hard if he wants to play longer in future sessions.

Fighting versus Playing

Watch for bared teeth, snarls and bites to the neck or face when your puppy engages your adult dog. These are common signs of actual aggression. If your pup intends to play, he may drop his head to the ground, prance around and bat at the other dog with his paws. Consistent hard biting, unprovoked lunges and guttural growling are signals of hostility rather than play. If your pup seems to harbor hostility for your older dog, you should separate them until you identify and resolve the source of the conflict.


Fear is a primal instinct in canines and is a common source of aggressive behavior. Your puppy may be fearful of your older dog's unfamiliar scent, size or demeanor. If you just brought him home, the stress of an entirely new environment may make him more likely to snap at other animals. Help puppies overcome fear by exposing them many smells, sounds and environments in a safe and controlled manner throughout early life. Separate your puppy from other dogs with a closed door and let them smell each other under the crack for a few days. When you do introduce them, let them meet up in an unfamiliar or "neutral" spot like an outdoor park, according to the Humane Society of the United States.

Dominance and Possessive Behavior

Your dogs may be fighting over who gets to eat first, sleep in the good spot or have a certain toy. Canines resolve hierarchy disputes and disagreements with posturing, vocalization and occasionally violence. Look for triggers when a fight breaks out between your dogs. If fights tend to happen in certain locations or during particular activities, look for things that could have started the conflict. Each dog should have his own food and water dishes as well as a secure place to rest. Give each dog some individual attention every day. Dogs can get very jealous when their peers receive affection.

Medical Issues

Taking your puppy to the vet is one of the first things you should do if he is acting aggressively. It's possible he's in pain due to an unseen injury or illness, so it's a good idea to rule this out with a checkup. Take this time to ask your vet about your pet's behavior. He may be able to offer a few tips for controlling bad behavior. If your efforts to curb your dog's hostility are ineffective, consult a canine behavioral specialist to discuss your options. Professional training does wonders for even the most unruly dogs.