Skip to main content

Puppy Life Stages: From Birth to Adulthood

Adrienne is a certified dog trainer, former veterinary assistant, and author of the online dog training course "Brain Training for Dogs."

Puppy Life Stages Explained

Puppy Life Stages Explained

The Stages of Puppy Development

Just like humans, puppies go through different stages of growth and development that are characterized by both physiological and psychological changes. This is why getting acquainted with the different life stages of dogs is important if you have a puppy. By recognizing these stages, you will benefit from knowing what to expect and be one step ahead when it comes to training your new puppy.

It's important to recognize that these stages are not clear-cut in all dogs. No exact timing of these stages can be determined—especially considering breed-specific variations. On top of this, certain life stages may overlap. Read on to learn more about the different life stages in dogs below.

  1. The Neonatal Stage (0 to 2 Weeks)
  2. The Transitional Stage (2 to 3 Weeks)
  3. The Primary Socialization Stage (3 to 5 Weeks)
  4. The Secondary Socialization Stage (5 to 12 Weeks)
  5. The Juvenile Stage (12 Weeks to 6 Months)
  6. The Flight Instinct Period (4 to 8 Months)
  7. The Adolescent Stage (6 Months to 36 Months)
  8. The Fear Periods (5 Weeks, 8–10 Weeks, 6–14 Months)
  9. Adulthood

The Common Stages of Dog Development


Neonatal (Infantile)

0 to 2 Weeks

Require stimulation from mom for pottying; primarily sleep, extremely vulnerable.


2 to 3 Weeks

Open eyes, respond to sound, interactive with environment, some mobility.

Primary Socialization

3 to 5 Weeks

Puppies engage in play and learn bite inhibition from mom and littermates; they also learn species-specific social cues.

Secondary Socialization

5 to 12 Weeks

Puppies learn social cues and develop motor skills. At 8 weeks they should be fully weened.


12 Weeks to 6 Months

Teething occurs; socialization must continue; spaying and neutering may take place.

Flight Instinct

4 to 8 Months

Dogs become more independent and listen less; start exploring on their own.


6 Months to 36 Months

Likened to the teenage phase in humans; dogs benefit from obedience training in this phase.

Fear Periods

5 Weeks, 8–10 Weeks, 6–14 Months

Confidence-building, training, and socialization helps dogs of all ages during the fear periods.


36 Months+

Maturity is reached; dogs require continued learning, training, exercise, and socialization.

1. The Neonatal Stage (0 to 2 Weeks)

Puppies are altricial species and are born blind and deaf, which makes them very vulnerable during the neonatal stage (or infantile stage). For this reason, they must stay close to their mother in order to be fed, stay warm, and survive; mom dogs tend to be particularly protective during this stage. The mother dog will also help the puppies to eliminate during this stage of development by licking their bottoms; this stimulates the puppies to pee and poop.

Puppies aren't very mobile at this age, and besides sleeping a lot, may attempt to crawl. It is common for them to twitch in their sleep in a state called "activated sleep," which helps them with development. At this age, neonates are also able to detect heat and body warmth and reunite with their mom and littermates in case they get separated.

2. The Transitional Stage (2 to 3 Weeks)

The transitional stage is defined as the time when a puppy's eyes open and the ear canals are no longer sealed shut (this usually occurs by the 14th day). At around 16 days of age, puppies can discern the source of a sound; by the 18th day, they startle from certain sounds. This phase of sensory awakening stimulates pups to interact with their environment.

On top of seeing and hearing, puppies become more mobile at this stage. They will take their first steps and start to interact more and more with their environment and littermates as well. Puppies still seek care from their mothers at this stage, however, and their brains are still fairly immature (activity remains the same whether awake or asleep as proven with electroencephalography).

5 Weeks +

5 Weeks +

3. The Primary Socialization Stage (3 to 5 Weeks)

During this stage in dogs, myelination occurs and the brain starts maturing. The axon of each neuron in the brain is coated with a fatty substance known as myelin, which helps the neuron to conduct signals more efficiently. The pup's central nervous system also develops at a rapid pace, paving the path towards conditioning and associative learning.

This is the time when pups start to explore more. They will start to move more and play with their mother and littermates. This is the stage that teaches puppies how to be dogs. They start to identify with their own species, a process known as "filial imprinting," and become accustomed to species-specific behaviors like body postures and vocalizations.

Since mother dogs at this stage frequently leave the den area for brief periods of time, puppies tend to form strong relationships with their littermates. This social adherence promotes the formation of social groups. This is also a prime time for learning bite inhibition. As the puppies play, rough bites evoke the other puppy to yelp and withdraw from play. This teaches puppies how to gauge the pressure of their jaws in order to keep on playing.

Scroll to Continue

Read More From Pethelpful

The mother dog will further impart this lesson. As the puppies latch on to nurse, their sharp teeth now hurt, so she will start to withdraw by walking away and showing other body language meant to tell the puppies to back off.

4. The Secondary Socialization Stage (5 to 12 Weeks)

This stage occurs from approximately 3 weeks to 12 weeks of age and is the most important time for human contact. Puppies at this stage must be socialized as much as possible because they undergo a grace period where they are much more open to being introduced to new people and new scenarios.

Here is a timeline of what to expect during the secondary socialization stage.

  • After 6 weeks, puppies will start exploring their surroundings and they will become more independent.
  • At 7 weeks, puppies are often temperament tested and are even considered ready to leave their breeder's home, but some advocate waiting a little longer until the puppy is at least 8 weeks (or older in certain small breeds).
  • At 8 weeks, electroencephalography shows adult-like patterns in puppies. Many puppies are generally put up for adoption at this age and are ready to go to their new homes. By now, they must have been fully weaned and have learned acceptable social behavior from mom. Through play fights with their siblings, puppies have improved their motor skills and have also learned to interpret body postures and vocalizations.

Why Socialization Is Critical

It has been proven that positive experiences during the socialization stage are likely to have long-term beneficial effects on the puppy's social behavior as an adult. According to one such study, puppies who weren't exposed to much human contact before 14 weeks of age weren't capable of forming normal relationships.

Responsible Breeders

Good breeders who have raised puppies in their homes will have exposed their pups to normal household sounds and other stimuli (the sound of a vacuum cleaner, sporadic handling, etc.). The great thing about puppies is that at this stage, they are very elastic mentally and able to learn from their new owners' behaviors.

16 Weeks

16 Weeks

5. The Juvenile Stage (12 Weeks to 6 Months)

During this stage, puppies go through a growth spurt and develop new teeth as the baby teeth start to fall out. For this reason, it's a good idea to keep a good supply of chew toys on-hand to redirect inappropriate chewing. Dogs at this stage are full of energy and will benefit greatly from lots of exercise and training.

Socialization efforts must also continue and dogs should be exposed to a variety of life experiences. (Socializing your dog is a life-long necessity.) Further socialization during this time will also reinforce what was learned in the earlier socialization period. A study by Appleby in 2002 even revealed that exposing dogs to busy, urban environments during this stage made them less likely to develop behavioral problems later in life.

When to Spay and Neuter

Most veterinarians recommend spaying or neutering your dog at 6 months of age. If you own a large breed, however, you may want to wait on spaying or neutering until your dog reaches its maximum size for health reasons. If you are adopting your dog, they were most likely already spayed at 2 months of age.

5 Months

5 Months

6. The Flight Instinct Period (4 to 8 Months)

During this time, dogs become more independent, confident, and even stubborn. This is a time when puppies may no longer linger by your side and they may be reluctant to come when called. In a natural environment, this period takes place when young canines are old enough (4 months old) to start leaving the den and start learning how to hunt and explore their surroundings.

6 Months +

6 Months +

7. The Adolescent Stage (6 Months to 36 Months)

This stage is likened to the teenage phase in humans. Expect some testing, reluctance to obey commands, and a rebound effect where your puppy may act as if he or she has forgotten all about what your basic commands mean.

At this stage, female puppies start to go into heat, however, there is some variation based on breed and size. There is also some variance as to how long dogs are in this stage: smaller dogs pass through it quickly until they hit 18 to 24 months, while large dogs may linger in this stage up until they are 36 months of age.

Continue to be consistent and firm when training your dog during this critical phase. Provide lots of stimulation, training, and exercise. Obedience training may be helpful in resetting goals and refreshing commands.

It is important to help pups overcome their fears through baby steps by creating positive associations.

It is important to help pups overcome their fears through baby steps by creating positive associations.

The Fear Periods (5 Weeks, 8–10 Weeks, 6–14 Months)

Several fear periods may take place during certain developmental stages in a dog's life. They can be observed at the following ages:

5 Weeks

Researchers have found that puppies at 5 weeks of age demonstrate a strong fear response toward loud noises and novel stimuli. They do, however, overcome these fears through gradual introductions, and if proven non-harmful, accept them as a normal part of their lives over time.

8 to 10 Weeks

Between the ages of 8 to 10 weeks old, puppies undergo another ''fear'' stage where they can be easily startled. It is important to help pups overcome their fears through baby steps by creating positive associations.

6 to 14 Months

At approximately 6 to 14 months, puppies may go through another fear stage. During this stage, it's important to build the dog's confidence levels by praising them when they exhibit confidence and taking the initiative to explore the world around them.



8. Adulthood

Most adult dogs have reached their final growth at this time but may continue to fill out and build muscle mass. Your dog may also be easier to deal with now that they have passed the rebellious teenage phase.

Dogs at this stage still benefit from advanced training to keep the mind stimulated and to continue to build confidence. Agility training may be helpful at this stage as well, or you may enroll your dog in a program to prepare for the Canine Good Citizen Test.

Providing ongoing training, mental stimulation, and socialization throughout a dog's life is especially important considering that the dog's brain remains elastic in adult life and is always capable of forming new neural connections. While it's true that the capacity for adjustment is substantially diminished compared to during the socialization stages of development, it remains important to keep your dog well-rounded.


  1. Dietz, L., Arnold, A.K., Goerlich-Jansson, V.C., Vinke, C.M. (2019). The importance of early life experiences for the development of behavioural disorders in domestic dogs. Behaviour, 155 (2-3). doi:10.1163/1568539X-00003486
  2. Howell, T., King, T., Bennett, P.C. (2015). Puppy parties and beyond: the role of early age socialization practices on adult dog behavior. Vet Med, 6, 143–153. doi: 10.2147/VMRR.S62081

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2009 Adrienne Farricelli


Adrienne Farricelli (author) on February 10, 2016:

Happy to hear your two Rottie boys bloomed into two wonderful companions. Kudos to you! I still have mine, they are 8 years old and I hope I get to enjoy them for a few more years. Wonderful dogs!

Ann Taylor on February 09, 2016:

I raised two rottie brothers. I got them very early in their life. If you think puppies dont go through what your children do, how wrong you are. They were excellent dogs. Not a mean bone in them. Loving and protective of me. Even the sheriffs dept., loved my dogs. They together ate the floor and started on the walls when i found them. We got through it. Never spanked them. They fought over who would ride in the front seat of my car. And knew whos turn it was on the next trip. Very educated and i miss them so much.

Adrienne Farricelli (author) on October 03, 2012:

Thanks for stopping by, this hub is actually pretty old. I wrote when I had to take a test on dog ethology a few years ago. I think my hubs improved since then, but I really need to improve this one when I have a chance.

Liz Elias from Oakley, CA on October 03, 2012:

Well done article; you've covered all the basics in a simple, straightforward manner.

I just wish the Beagle we had many years ago, when my kids were little could have read your piece.. ...apparently, he did not learn anything from his mother. LOL

Voted up, interesting and useful.

Adrienne Farricelli (author) on October 03, 2012:

I am happy you found my hub on puppy life stages helpful! kind regards!

retard1 on October 03, 2012:

Thanks it was very helpful

APatt on August 25, 2011:

THanks that helped a lot

trainmypuppy from Oxford on March 01, 2010:

Im new to hub pages and will follow your articles on dogs and puppies with interest

buddy12love on September 09, 2009:

there so cute

ronibgood on June 13, 2009:

Very good information. Thanks.

Related Articles