“My dog excelled in puppy class. He had a solid recall, amazing leash walking skills, and could focus on me whenever I asked him to by the end of the course. He was such a clever puppy! He could sit, lie down, and stand on cue, and he could even do a few tricks. He was confident in everything he did. However, I’m not sure what has happened recently, but he has started to act out. He blatantly refuses to come when I call him, pulls on the leash during walks, and seems less social. He has begun to react negatively to other dogs and appears somewhat scared of the world around him. What could be happening? Is this a genetic issue, and should I expect this behaviour to continue for the rest of his life, or is he simply becoming increasingly naughty”?

Perhaps you’ve heard people mentioning the above, or maybe you’ve even experienced it yourself. Let’s take a look at possible reasons for this change in behaviour, and usually, it has very little to do with genetics or being naughty.

As dogs mature, they progress through various developmental stages. I discussed puppyhood in other articles, so after the cute puppy phase, the young dogs will reach adolescence. This occurs roughly between 6 and 18 months of age, and in many cases, this period brings significant behavioural changes.  So, why is that?

Hormonal changes

Hormonal changes are a significant aspect of a dog’s development as they enter puberty, which typically occurs between six months and a year of age, depending on the breed. These hormonal fluctuations can lead to notable shifts in behaviour, heavily influenced by the dog’s sex.

For male dogs, an increase in testosterone levels is a primary factor driving behavioural changes. This surge often results in a heightened likelihood of marking territory by urinating on various objects or structures in their environment. As they navigate their surroundings, males may exhibit increased intensity in behaviours such as sniffing and seeking out scents. Their wandering tendencies may also escalate, and they might attempt to escape to explore new areas or engage with other dogs. Additionally, males may be more prone to pulling on the lead during walks, driven by an urge to reach compelling scents or engage with other animals. Moreover, they may exhibit more unsettled behaviours, displaying restlessness and an increased interest in their surroundings.

Female dogs, on the other hand, usually experience their first oestrus cycle, commonly referred to as a heat cycle, around the age of seven months. There are four distinct stages in a dog’s reproductive cycle: Anestrus, Proestrus, Estrus, and Diestrus. During a female dog’s “heat” cycle, her body undergoes hormonal changes, primarily due to fluctuations in estrogen and progesterone. For this article, I don’t want to explain female heat cycles in detail, but because they can be the cause of behavioural changes, I need to mention them.

In the Proestrus stage, the female’s body prepares for potential mating. She experiences an increase in estrogen levels, which leads to physical changes such as swelling of the vulva and a bloody vaginal discharge. Her behaviour may also change during this time; she may become more affectionate, but is not yet receptive to males.

The Estrus stage, often referred to as the “heat” phase, is the most fertile period and lasts about 5 to 14 days. During this stage, estrogen levels peak, and progesterone begins to rise. The female becomes receptive to mating and may show increased interest in male dogs. These hormonal changes prepare her body for potential pregnancy and influence her reproductive behaviour.

The Diestrus stage starts when the dog no longer displays the typical signs of estrus, such as a willingness to be mounted by a male. During this phase, the hormone progesterone increases significantly, reaching its peak approximately 2 to 3 weeks after ovulation. This surge in progesterone is crucial for maintaining pregnancy, occurring whether or not the dog is actually pregnant. After peaking, progesterone levels remain elevated for about 1 to 2 weeks before gradually declining over a period that can last anywhere from 10 to 30 days. Diestrus ends when progesterone levels return to their normal baseline. Something interesting, though, is that pseudopregnancy can occur as well. Pseudopregnancy, also known as false pregnancy, is a condition that can occur in female dogs (bitches) following a heat cycle, specifically during the diestrus phase. This phase typically occurs about two months after ovulation when the body prepares for a potential pregnancy, regardless of whether mating has occurred.

During pseudopregnancy, several physiological changes take place. One of the most notable is the deposition of abdominal fat, which can alter the dog’s physical appearance. Additionally, there is an increase in mammary gland development, and some bitches may begin to produce milk, leading to lactation. These changes can trigger maternal behaviours, such as nesting and caring for toys or other objects, mirroring those seen in a dog that is genuinely pregnant.

Interestingly, studies have shown that there are no significant differences in progesterone concentrations between bitches that exhibit pseudopregnancy and those that do not experience this condition. This suggests that the hormonal changes associated with pseudopregnancy do not stem from elevated progesterone levels.

Despite ongoing research, the precise reasons behind the onset of pseudopregnancy remain unclear. It is considered a natural response to hormonal fluctuations in the reproductive cycle. While it is typically benign, it can sometimes lead to behavioural changes that may require attention from pet owners.

Throughout this stage, female dogs lose their attractiveness to males and show a marked disinterest in mating. Additionally, the external appearance of their genitalia remains mostly unchanged during diestrus, resembling the state it will be in during the subsequent phase known as anestrus, which is a period of reproductive inactivity.

It’s important to note that there can be variation in the timing and signs exhibited during each stage, depending on the individual dog. This cycle can introduce a range of behavioural changes, some of which may be subtle, while others can be overt and pronounced. During this time, a female dog’s behaviour might include signs of lethargy, where she may become less active than usual. She might also seek increased closeness to her owner, and it might feel like she is showing a desire for companionship and reassurance.

Additionally, some female dogs may start to exhibit behaviours such as collecting and guarding items, which can manifest as a protective instinct over toys or other belongings. During this period, they may become more sensitive to touch, displaying an increased need for personal space or, alternatively, longing for physical affection. Their tolerance levels regarding interactions with other dogs may also change; some may become less tolerant and more defensive when approached, while others may exhibit increased boldness and playfulness.

Finally, it is not uncommon for female dogs in heat to vocalise more frequently, expressing their emotions or needs in varying tones. These vocalisations can range from whining to howling, as they may be trying to communicate their presence and attract attention from male dogs. Overall, these hormonal surges can lead to a complex mix of behaviours that owners can easily misinterpret as the dog being naughty.

We can even dig a bit deeper and say that during adolescence, significant transformations unfold within a dog’s brain, reshaping its structure and function in profound ways. A teen dog’s limbic system, which governs emotions, and the prefrontal cortex, the area responsible for decision-making and impulse control, are still maturing. This ongoing development can manifest as impulsive behaviours and difficulty with self-regulation, making this phase both exciting and challenging.

It’s vital to recognise that your dog’s perceived disobedience is not a deliberate act of defiance but rather a natural response to the complex changes occurring in their brain. Much like human adolescents, dogs require time to cultivate their capacity for organisation, impulse regulation, and the ability to weigh risks against rewards. This developmental journey leaves both dogs and humans susceptible to risk-taking behaviours, which can lead to unpredictable choices.

Interestingly, the maturation process varies across different breeds. Larger breeds, such as the Komondor, often take longer to reach full cognitive maturity compared to their smaller counterparts, like terriers. This variation impacts how one should approach training and sets realistic expectations for behaviour. Generally, a dog’s brain completes its neural development around the ages of 24 to 36 months. This includes critical areas of the brain tied to advanced cognitive functions and social interactions, which are essential for navigating complex environments.

During this early phase of maturation, vital inhibitory hormones, such as gamma-aminobutyric acid (GABA), are not fully developed. This hormonal immaturity results in heightened impulsivity, often causing teen dogs to act without thinking or to engage in riskier behaviour. GABA plays an essential role in regulating behaviour by calming excessive neuronal activity. Without the complete development of these hormones, young dogs may struggle to self-regulate, leading to spontaneous reactions and emotional outbursts in situations that would have previously elicited little to no response.

Beyond these neurological changes, the adolescent brain is exceptionally pliable, remaining adaptable and receptive to the influence of experiences. While this capacity for change persists throughout their lives, adolescence is a particularly crucial period for owners to focus on continued training based on positive reinforcement.

Engaging in this type of training not only helps rebuild foundational skills, such as reliable recall, but also reinforces all the wonderful behaviours that you appreciate and wish to see repeated, like maintaining composure in the presence of other dogs or distractions. By consistently nurturing your dog’s learning and practising the skills they have already learned during this formative time, you offer them the stability and guidance they need to navigate this sometimes-overwhelming chapter of their lives with greater confidence.

All this, however, is temporary, and once you have guided your dog through this teenage stage, you will have a companion that you can enjoy spending time with for the rest of his life.