Let’s Talk about Behavior Change in Adolescent Dogs a.k.a. Where Did My Sweet Puppy Go?

Image shows a black and white Portuguese Water Dog with his mouth open, lips retracted, showing his teeth.

You’ll notice right away when your puppy or dog reaches adolescence. He will become more independent, and there will be other behavior changes. One minute, your puppy is sweet, following you around, learning new things, and meeting new people. But as he grows and matures, it seems like your puppy, who used to love everyone—people and dogs—has suddenly become selective about who he likes and doesn’t. And he makes that obvious. You’re left wondering, “Where did my sweet puppy go?” Owners frequently notice changes in behavior when their dog reaches adolescence. But why?

The adolescent period in dogs runs from sexual maturity, 6–9 months of age, to social maturity, 2–3 years of age. Adolescence is typically a period of increased independence and behavioral changes.  Owners often feel like new behaviors, like barking at strangers or other dogs, come out of the blue. Further investigation shows a “louder expression” of a previously displayed behavior. For example, a puppy who is “a little shy” or “skittish” around new people may begin barking at people as an adolescent. People often attribute this behavior to the dog being protective, but that is rarely the case. “Skittish,” “shy,” “slow to warm up to people,” and “barking at people” are often different expressions of the same emotion. 

Behavior Changes in Adolescent Dogs

A brown and white dog biting the base of the tail of another dog.

I (Marge) frequently receive inquiries from people with puppies who developed new behaviors in adolescence. Typically, the dog displays some type of behavior described as aggression (barking at guests, other dogs on walks, people on the street, their children’s friends, and so on). Maybe they “loved people” when they were younger or seemed to play well with the neighbor’s dog and now show aggression. It may even seem like the dog is being protective because he barks loudly when people he doesn’t know approach or come to the door.

First Things First

Your first step is to consult your veterinarian whenever your dog has a sudden change in behavior. Many physical conditions can cause changes to your dog’s behavior. Something as simple as an ear infection can cause your usually friendly dog to react negatively if someone pets his head and touches his painful ear. First and foremost, have your veterinarian conduct a pain and medical evaluation.

Second Things Second

Do not skip this part, even if your dog “loves everyone.” Learn about or refresh your knowledge of canine body language. I (Marge) hope you were able to learn about canine body language when your dog was a young puppy. Without that information, you really cannot socialize him effectively.  So, if you didn’t get that information then, you need it now. 

I’ll give you my favorite resource on this and admit up front that I am biased because I helped create it. My co-author, Eileen Anderson, and I included an entire chapter on canine body language in our book, Puppy Socialization: What It Is and How to Do It. You cannot, I repeat cannot, help your adolescent dog feel better about the things that worry him if you cannot recognize the more subtle signs of fear and anxiety in dogs. I also recommend the free download of Body Language of Fear and Anxiety in Dogs by the late Sophia Yin.

Let’s Take a Look

The following photos were taken during a one-hour session. Through his body language, this adolescent dog shows us how he feels about being in a new location. While most of us recognize photo number one as a fearful dog, many people would not recognize photo number 2 as fear-based behavior. The dog noticed people walking at a distance (he worried about people), made himself taller, and started to bark. The first two photos were taken less than 30 minutes apart. The barking at people did not come out of the blue. The first photo tells us he is uncomfortable in this new situation. The second photo shows us an escalation of that behavior. As we progress to photos 3 and 4, we see the dog’s lower jaw begin to soften, his tail is held in a more neutral position, and all of his body muscles are softening. Fortunately, this dog is a fast learner. As you can see in the photos, our training was effective, and he could relax and feel safe throughout our session.

Listen to Your Dog

When your dog tells you he’s uncomfortable, listen. The more subtle signs of fear and anxiety in dogs (yawning, licking their lips, whites of their eyes showing, and more) typically precede the more overt signs (barking, growling, lunging, air snapping, and biting).  The behaviors in both groups are referred to as distance-increasing behaviors. They are intended to increase the distance between the dog and whatever he directs his behavior towards. Your dog is telling you he needs more distance. Give it to him. Suppose a dog keeps “whispering” to us (the more subtle signs of fear and anxiety: yawning, lip licking, pacing, moving away) that he is uncomfortable, and we don’t listen. He may escalate his behavior and begin “shouting” (barking, growling, lunging, air snapping, and biting) so we pay attention that he is uncomfortable. Learn to listen to the whispers.

What to Do Now

Get professional help. A qualified, certified professional can teach you how to help your dog and change how he feels about the things that worry him. I recommend someone certified through the Certification Council for Professional Dog Trainers. Their credentials will appear after their name as CPDT-KA and/or CBCC-KA. Another good credentialing body is the International Association of Animal Behavior Consultants (IAABC).

Sometimes, dogs are so fearful, worried, or anxious that they need more expert-level help on their team. Veterinarians who specialize in animal behavior are the ultimate experts in behavior change. Your veterinarian can help you reach out to a veterinary specialist.

Most owners will need a credentialed professional to help them help their dog feel better about the things that worry him. In addition to understanding the science behind behavioral change, your observation and timing skills are critical to success. And, unless you do it for a living, it can be hard to pull that all together on your own without a coach. Even professional athletes use coaches. 

Your certified professional will help you change how your dog feels about the things that worry him through a process called counter-conditioning and desensitization (CC/DS). It is concisely explained here at CARE for Reactive Dogs

What Not to Do Now (Or Ever)

Do not punish your dog for subtle or overt signs of fear and anxiety. You may feel embarrassed, angry, or afraid if your dog snaps or barks at someone. He is behaving that way because he needs space. Give it to him immediately. Physically punishing, scolding, or telling him “it’s okay” or “this person is a friend” will not make him feel better; in the case of punishment, it could make him feel worse. Punishing a worried, anxious, or fearful dog will likely increase those emotions. That makes sense, doesn’t it?

Do not put him in situations that worry him unless you are working with a credentialed professional and it is part of his CC/DS plan. Let’s say your dog snapped at the last person that entered your home. The next time someone enters the house, your dog should be safely confined (behind a closed wooden door) when someone enters. If your dog snaps or bites the next person, that behavior is not out of the blue. It is a predictable escalation in his behavior. You can prevent that. Don’t put him in situations where he has to shout (escalate his behavior) so you can understand he is uncomfortable in that situation.


During adolescence, your puppy’s brain continues to develop. That is part of the reason adolescence seems so challenging. Our dog may be fully developed physically, but his brain is not fully developed. You still have the opportunity to make positive changes in his long-term behavior. It all starts by listening to your dog when he tells you he’s uncomfortable (learning to read the more subtle signs of fear and anxiety in dogs). You can’t help your dog feel better about what worries him if you can’t identify what worries him. Use counter conditioning and desensitization. Get help from a credentialed professional now so you can learn to support your puppy through this typically difficult stage in his behavioral development.

Copyright 2024 Marge Rogers and Eileen Anderson

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