Developmental milestones

One of the most crucial aspects of canine health and behaviour we encounter is understanding the developmental milestones that shape a dog from puppyhood to adulthood. These stages influence how dogs behave and how they interact with their world, people, and other animals around them.

This article will explore the key milestones in a dog’s life, explain why these stages are significant in terms of behaviour, and highlight the influence of genetics, prenatal experiences, and early socialisation on a dog’s growth and behaviour.

A LITTLE BIT ON BEHAVIOUR
Canine behaviour is a topic in itself and beyond the scope of this article. Before diving into specific developmental stages or ‘milestones’ of our dogs, it’s important to understand that a dog’s behaviour is not guaranteed, and it is not static.

Behavioural changes are influenced by many intrinsic and external factors, including genetics, the environment, their experiences (even prenatally), their diet, health, and their feelings (for instance, feeling hungry or frustrated). While it is important to breed from carefully selected parents with ‘good genetics’ (healthy with desired physical and behavioural attributes), whether or not puppies develop these desired traits and behaviours is not just down to genetics.

These intrinsic and external factors (while occurring throughout the dog’s life) will occur at certain specific stages in a dog’s life, which, for simplicity, we will refer to as ‘milestones’. These milestones are important to recognise if we are to help nurture our dogs to become the well-rounded, confident family dogs we hope them to be.

PRENATAL STAGE
Early experiences, starting from the prenatal stage, play a significant role in shaping a dog’s behaviour. A dog’s mother, for example, has a profound influence on her puppies, not only during the early weeks of life but also while she’s pregnant. Maternal stress or health can influence the development of the puppies, including their ability to cope with stress and form social bonds later in life.

PUPPYHOOD

The Critical Socialisation Period (0-12 weeks)
The first 12 weeks of a dog’s life are considered the most critical in terms of behaviour. This period is divided into three phases: neonatal, transitional, and socialisation.

Neonatal Period (2-3 weeks)

During the first two weeks of life, puppies are largely dependent on their mother. They are born blind, deaf, and unable to regulate their own body temperature. Their behaviour is largely instinctual—mainly focused on seeking warmth and the safety of their mother for feeding.

Early touch and gentle handling (minimal stress) can lead to more confident dogs better able to cope with mild stress. However, excessive stressors, such as too much handling, being cold, or being hungry, may have profound negative impacts on development and behaviour.

Transitional Period

By the end of the second week, puppies’ eyes and ears begin to open, marking a period of increased sensory development. They start to become more aware of their surroundings, reacting to sounds, light, and touch.

As the sensory system matures, puppies begin to engage in more active exploration. This is also when they begin to crawl, walk, stand, and play with their littermates, fostering early social behaviours. They may also start to toilet by themselves outside of the sleeping area.

Socialisation Period

The socialisation period is arguably the most important phase for behaviour development. During this window, puppies are particularly sensitive to new experiences, and positive exposure to various stimuli (other dogs, people, sounds, sights) is crucial.

Puppies that receive ample socialisation during this time tend to be more adaptable and less fearful of new experiences later in life. Appropriate socialisation teaches puppies essential skills, like how to interact appropriately with other dogs and humans. They learn bite inhibition through play with littermates, and their brains are highly receptive to forming new connections.

For those selecting a breeder, this period highlights the importance of choosing a breeder who prioritises early socialisation. By 8 weeks, when puppies are weaned and leave their mothers, vaccinations allow them to start integrating with other dogs in different environments. Until then, familiarising puppies with car journeys and household noises like vacuum cleaners is essential.

The juvenile period (3 months to onset of sexual maturity)

After the first few months of life, puppies enter the juvenile period. This is a time of significant physical and social development. Puppies begin to explore their world with increasing confidence, and their interactions with humans and other dogs become more complex.

During this stage, early training, including house training and basic obedience, takes root. Puppies also test boundaries and may exhibit behaviours such as chewing, digging, and vocalising—all normal behaviours that need to be correctly managed.

From a behavioural perspective, this is the time when puppies’ personalities begin to solidify. Genetics set the foundation, but their environment and experiences shape how confident, anxious, or reactive they become as adults. Positive reinforcement during this stage increases the likelihood of desirable adult behaviours.

Adolescence

Adolescence, spanning from 6 months to about 2 years (depending on breed/size), is often the most challenging phase for dog owners. This stage is characterised by hormonal changes and increased independence.

Adolescent dogs may test boundaries and exhibit behavioural challenges such as barking, destructive chewing, or attempts to escape. Some may experience separation anxiety or react strongly to new stimuli due to less mature coping mechanisms. Continued training, socialisation, and consistency are key in guiding dogs through this phase.

ADULTHOOD
By the time dogs reach adulthood, typically around two years of age, their personalities are largely established. They will have settled into a routine and exhibit more predictable behaviours.

While adult dogs are generally less energetic than adolescents, they still benefit from training and engagement. Any lingering behavioural issues, such as anxiety or aggression, should be addressed with patience and, if necessary, professional guidance. Training and socialisation remain important for maintaining well-being, and consistency in corrective actions is crucial.

GERIATRIC (OLDER AGE)
In a separate article, we will discuss the ageing dog and their specific age-related requirements. This stage must not be overlooked, as age-related illnesses such as arthritis, dental disease, or cognitive dysfunction can significantly affect behaviour. Sensory losses, including sight and hearing deterioration, may cause older dogs to feel more vulnerable, sometimes leading to intolerance or aggression.

In summary
Understanding a dog’s developmental milestones is essential for fostering positive behaviour and ensuring a balanced relationship between dogs and their owners.

Early socialisation, particularly during sensitive periods, is crucial in preventing future behavioural problems such as fear, aggression, or anxiety. A lack of early socialisation can result in dogs that are fearful of strangers, other dogs, or new experiences, which can lead to behavioural problems later in life.

Moreover, knowing how genetics and early experiences shape a dog’s temperament helps veterinary professionals and owners tailor training strategies that align with the dog’s inherent tendencies. A well-socialised, well-trained dog is not only easier to manage but is also more likely to enjoy a happy, healthy life.