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The Teenage Stage: Hormones, Neurons, and Brain Development

Teenage (8 month old) Tuna interrupted while eating grass.


Your dog is reaching sexual maturity.

This brings about a whole new set of behavioral challenges. Adolescence is the time in a dog’s development when they are capable of mating. In a nutshell, puberty!

Adolescence can start as early as five months, and stick around until your dog is about a year or two old. Smaller dogs tend to mature faster than large breed dogs. The “teenage” stage can feel a lot longer in a Labrador compared to a Yorkshire terrier!

Evolution shaped these behaviors to help canines find a mate as quickly as possible. Even if they are spayed or neutered, your dog will go through behavioral changes caused by floods of hormones, most notably bolstered confidence. It can vary depending on the individual, but both male and female dogs can urine/scent mark to define territory and announce availability for mating. Many owners start to notice more dog-dog scuffles start to pop up if they take their dogs to parks or daycares. Suddenly they are counter surfing, body slamming during play, and ignoring recalls when off-leash. Everything else just got a whole lot more interesting than listening their human!

Some other behavior changes you might notice:

  • Escaping and exploring

  • Stealing

  • Counter and table surfing

  • Purposeful mouthing and play biting

  • Excessive jumping

  • Digging

  • Barking

  • Destruction

  • Resource guarding


Should you spay or neuter your dog?

Overbreeding/population is a real problem in the U.S. If you’re not a professional breeder registered with your county and state doing health screenings and temperament tests, don’t breed your dog. It can be dangerous for your dog, and perpetuates overcrowded shelters/rescues.* You don’t want a litter of accidental puppies on your hands. It’s expensive and potentially dangerous for your dog. I had a family member receive an accidental puppy from a friend’s un-fixed female Boston terrier. A Boxer had broken into their yard, and mated with the terrier. Due to the size difference, the Boston terrier died when the puppies were born.

* I'm not saying don't get a puppy from a reputable breeder, just don't DIY dog breeding *

Spaying or neutering also reduces the risk of cancers, UTI’s, and hyperplasias.

All that being said, the evidence is inconclusive on if spaying or neutering actually affects behavior. Some professionals swear up and down that neutering a dog will decrease aggression, marking, escaping, etc. I can tell you at least anecdotally that I’ve not seen differences in my client dogs after a spay/neuter. There are SO many reasons for a dog to be reactive or mark with urine, and most dogs I see with those issues are spayed/neutered.

Studies with conflicting conclusions towards effect of spay/neuter on behavior (Lindsay, Steven, 2001):

  1. Lieberman (1987) reported a study from 400 dogs showing that 200 puppies fixed at 6-12 weeks old had significantly reduced aggressive behaviors compared to puppies fixed at 6 months of age

  2. Salmeri and coworkers (1991) challenged the above findings after finding puppies fixed at 7 weeks and 7 months of age showed no discernible difference in behaviors like barking and aggression

  3. Two experiments (Voith and Borchelt, 1982) and (O'Farrell and Peachy, 1990) showed a significant number of female dogs with an increase in aggression after being spayed.

Veterinarians seem to be trending towards waiting a bit longer (it used to be 6 months across the board) to get your pet fixed if possible. The reproductive hormones that cause trouble are also responsible for overall health and development, so it’s a balancing act between those. Discuss with your vet when would be best to get your adolescent dog spayed or neutered.


The brain of an adolescent dog is physically different compared to an adult dog.

I recently listened to an episode of The Bitey End of the Dog podcast where guest speaker Dr. Kathy Murphy spoke about the study of neuroscience and aggression in dogs. She had some really great insight on adolescent dog brains:

In addition to the hormonal changes happening in their teenage brain which drives their behavior, they don’t have a fully formed adult brain yet. It’s a crazy time during their brain development. In adolescence, their inhibiting neurons are are still devoloping. These neurons inhibit excessive behavior, pain, and arousal, etc. They are meant for dampening down reactions to stimuli. Exciting neurons get them excited and amped up. They mature much faster than the inhibitory neurons. A fully formed, healthy, adult brain will have a balance between the exciting and inhibiting neurons. This is what keeps healthy adults emotionally and behaviorally stable.

The adolescent brain is full of excitation and no inhibition. This is why puppies and adolescents really struggle with resisting temptation and short attention spans. Their brain literally isn’t physically capable of what is being asked. This is why it’s important to set them up for success. Try not to punish or retaliate against adolescent dogs for eating a hole in the floor when unsupervised or ignoring a recall.

Behavior in young dogs is going to be erratic.

Difficult behaviors during adolescence is the main reason teenage dogs get surrendered to shelters or rescues. Even the best-socialized, well-trained dogs can become T-Rex Demons while their brain chemistry is finding it's balance. They might be snuggly one moment and then ignore their owners altogether the next while they tear around like the Tasmanian devil. Give them some leeway and understanding. Their brain is physically not the same one they will have as an adult. The responses they receive from us during this stage of inhibition instability is what is going to set the stage for the bond you share as an adult!

Some young dogs will go through a fear stage during adolescence, where they are more sensitive to new things or sounds. It’s important to continue with positive socialization through this stage so events do not become traumatic to your dog. If your puppy was well socialized before 16 weeks of age, they should have a decently developed “bounce back” after a startle event.

Remember if you reinforced something “cute” as a young puppy like face licking, chewing, jumping to say hi, etc. it might quickly become not cute for an adult dog. Be consistent with manners training, boundaries, and not encouraging unwanted behaviors. The hardest part is getting all the friends and family on the same page. It only takes one excited and well-meaning person to reinforce a jumping dog after spending three weeks teaching an alternate behavior. The same goes for feeding food at the table, or allowing your dog to steal food off the counter because it was left unsupervised!

Too much to handle? Let me help!

Try to be consistent with your dog training plans (especially recall and impulse control exercises), and use higher value treats. Mental stimulation, exercise, and clear boundaries are your best friend during this time. You’ll come out the other side with a well-rounded and calm adult dog if you just stick with it!

Many of my clients are adolescent dogs. If you're feeling stuck or frustrated, reach out for a free training consultation. I have a private program designed specifically for my teenager clients!


Lindsay, Steven (2001). Handbook of Applied Dog Behavior and Training: Volume Two: Etiology and Assessment of Behavior Problems. Ames, IO: Iowa State University Press.

Shikashio, M. (Host). (2022, June 27). Dr. Kathy Murphy (No. 5) [Audio podcast episode]. In The Bitey End of the Dog.


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