Puppy development: from birth to adolescence

Scientific research proves that growing puppies have different nutritional needs to adult dogs. To give your puppy the best start towards a long and healthy life, it’s important to provide them with a diet that’s specifically designed for puppies throughout the growth phase. The length of this phase will depend on the size of the dog with smaller breed puppies maturing much more quickly than larger breeds.

Early socialisation and training experiences leave a positive, lasting impression on a puppy and helps him to develop into a well-mannered adult dog. The development of puppies can be divided into five distinct stages:

  • The Neonatal Period.
  • The Transitional Period
  • The Socialisation Period
  • The Juvenile Period
  • Adolescence

These developmental periods are followed by adulthood.

key milestones

The neonatal period (Birth 2 weeks)

Through this period puppies are relatively helpless, relying entirely on their mother.

At this stage, the puppy spends the majority of its time either sleeping or eating. Puppies’ eyes and ears are closed when they’re born but they are sensitive to touch and smell. Their eyes open at around 10-14 days old but puppies do not respond to light and moving stimuli until the transitional period (two to three weeks of age).

Neonatal puppies have limited movement and are only capable of a slow crawl. They’re not yet able to stand and support the weight of their body.

During this period a puppy will actively seek its mother. If separated from its mother, a puppy will start to vocalise and crawl, swinging its head from side to side in an attempt to find her. At this stage puppies have a reduced ability to regulate their body temperature and so rely on their mother and littermates for body heat.

In the neonatal period puppies are only able to feed by suckling from their mother. Urinating and defecating is stimulated by the mother licking the anogenital region, and she keeps the nest area clean by eating any waste products.

Handling puppies for short periods during the first two weeks of age has been shown to be beneficial to their behaviour later in life.

At birth

Your puppy can crawl forwards but his eyes and ears are closed.

Up to 24 hours

It is essential that puppies consume colostrum in the mother’s milk within the first 24 hours after birth, as this provides contains antibodies and other immune substances that help protect newborn puppies from disease.

2 weeks

Your puppy’s eyes and ears start to open, although vision and hearing can be poor at first.
Your puppy is very prone to worms so they need to have their first worming treatment now.

The transitional period (2-3 weeks)

This is a period of rapid change and you will notice your puppy beginning to show some of their adult characteristics such as showing their first social signals by practicing growling and wagging their tail, they will respond to light and movement as their eyes begin to open and they start to respond to noise as their ear canals open. They will also start play fighting with their siblings.

The puppy starts to show an interest in semi-solid food (but continues to nurse from their mother too). They can now lap water from a dish.

Anogenital licking of the puppy by the mother is conducted from birth as puppies need stimulating to pass urine and faeces regularly. This is no longer needed now as puppies at this age now begin to relieve themselves naturally, away from the nest.

The socialisation period (3-12 weeks)

This is probably the most influential period of your puppy’s life and much of what is learned during this period may last throughout their life. During this time they develop social skills and learn about their environment. It’s essential during the later part of this period that they encounter as many of the people, objects and situations they might encounter in later life, including being left alone for short periods, visiting the vet and travelling in the car.

At 3 weeks the puppy begins showing a startle response to loud noises, they will try standing and walking and may make their first attempt at barking!

Dogs have two sets of teeth, just as humans do, their first set are ‘deciduous teeth’ often referred to as ‘milk teeth’ and they start to erupt at this age.

6-9 weeks

6 weeks is the time for your puppy’s first vaccination. (The second one is between two and four weeks later.)

At 6-8 weeks, your puppy will now be fully weaned and enjoying four or five small meals a day.

At 6-9 weeks, puppies usually leave their mother and littermates to go to their new homes. Speak to the breeder about what vaccinations and worming treatments they’ve had. It’s also a good idea to talk to a vet about vaccinations, puppy parties and neutering before you collect the puppy. This is a key time as your puppy is most responsive to socialisation so it’s a good idea to experience a wide variety of situations, people, noises and environments so that they develop all- important social skills for later life. You can take them out before their vaccinations are complete, as long as you carry them and don't allow them onto the ground or in areas where other dogs may have been.

8-12 weeks

Your puppy’s meals can now be reduced to feeding three meals a day. This is also the timing of the puppy’s second vaccination, it is important to check with your vet how many days to wait after this vaccination before your puppy is safe to go outside in public areas and meet other dogs.

The juvenile period (12 weeks through to adolescence)

This is the last puppy development stage. By the time your puppy growth reaches the juvenile period, most of its major changes have taken place. All of the sense organs will be fully developed and puppy growth rate will slow down.

However, the juvenile period continues to adulthood and they will need to stay on puppy food until then. This can be any time from one year (for smaller breeds) up to 18-24 months for large and giant breeds. During this time your puppy will still be growing and physiological changes will be happening that you might not be aware of.

Puppies have similar motor skills to adults by the age of six months, although this can vary according to the individual dog and their environment. And, by about seven months, adult teeth will replace the milk teeth.

You’ll need to carry on socializing your puppy and introduce a training programme. Puppies have a short attention span and can be excitable so keep training short, consistent and fun.

Sexual maturity is marked by the first season in bitches and the ability to achieve a fertile mating in dogs. This usually occurs at around six to seven months, although males may show sexual interest in females before then.

However, even though they are sexually mature they’re still not considered adult dogs at this stage.


Puppies mature very quickly, and the smaller the breed, the faster they reach maturity. In small breeds, adolescence can start as early as 5 months. In larger breeds it can start as late as 9 or 10 months, and very large breeds might not go through adolescence until 12-18 months.

Depending on the size of your puppy’s breed, adolescence will last for between a few months and a year. (After dogs reach maturity, their rate of ageing slows down. Despite the “seven years” myth, mature dogs age at the rate of about four dog years for every human year.)

Recognising adolescence in your dog

When your dog reaches adolescence, you might see some or all of the following behaviours:

  • aggression
  • plenty of energy
  • very short attention span
  • poor socialisation
  • disobedience
  • wandering
  • leg cocking (males); and
  • obsessive mounting behaviour.

Coping with your dog’s adolescent phase

After all the hard work you’ve put into your puppy’s training, your dog’s adolescence can be a frustrating time.

Instinct is telling your dog that it is time to get out and about, showing off, leaving their scent everywhere and seeing off competition. Your challenge is to allow your dog some freedom without getting into too many uncomfortable situations with other dogs and their owners.

Ritual fighting

When adolescent dogs challenge each other, a scuffle is almost inevitable, but it’s very unlikely to result in injury. Once one has established itself as ‘top dog’, the fight usually ends in a few seconds. And a part of adolescence is learning the rules. So you don’t need to keep your adolescent apart from other dogs – they’ll simply grow up frustrated and poorly socialised. (Properly socialised puppies will “mock bite” without causing injury – if yours does injure another, they will need specialist “bite inhibition” training.)

Intensify the training

At this time, it’s essential to keep working on every aspect of your dog’s training: give them lots of praise and rewards to boost their self-esteem while they work off some of their extra energy. Don’t give up – adolescence won’t last forever.