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A puppy’s developmental stages

Updated 26 November 2024
Read time: 7 mins
article author
Written by Corinne Homer
Copywriter
article author
Reviewed by Dr. Linda Simon
Team Vet

Getting a new puppy is super exciting, no matter what. After all, you’re bringing a dog into your life right at the beginning of theirs - and they’re sure to quickly love you just as you love them. 

As a new puppy owner, it’s important to understand what stage of puppyhood they’re at, and exactly how to cater to their needs. Let us explain what happens to a puppy as they grow - from a teeny puppy foetus, to a bounding 18 month old pooch.

 

Still in the womb

Right from conception, a dog’s life progresses at a much quicker speed than a human’s, and pregnancy is no exception. It takes around 63 days on average, for a fertilised egg to develop and emerge as a newborn puppy. 

To be specific, after the mother’s egg is fertilised, it becomes a cluster of cells called a blastocyst, which then develops into an embryo with a spinal cord and heart. After around 30 days it can be called a foetus - and resembles a tiny puppy, with a coat, eyes, ears and other sensory organs. 

Pregnant dogs usually have a litter of puppies. Smaller breeds have fewer pups - around 4-6 babies - while large breeds can have 8-12 puppies or more! During this prenatal stage, it’s incredibly important for the mother dog to be well-nourished and carefully looked after so that both mum and babies are kept safe and healthy. 

 

The Neonatal Stage: Birth to 2 weeks

 

The puppies have been born! A puppy is going through its very first experiences in this crucial neonatal stage.

During this stage, the tiny puppies will develop rapidly and gain weight every day. They’re fed solely on the mother’s milk, called colostrum - crucial for growth because it’s rich in antibodies, providing the puppy with passive immunity against common germs.

At this point, they can barely see or hear, as their eyes and ears are closed. They also can’t stand or move very much at all, except to wriggle. They also can’t regulate body temperature, so are entirely dependent on their mother to nourish them and keep them warm with her body. 

Their acute sense of smell is well developed, however, and they’ll sniff out their mother to seek milk and comfort. 

 

The Transitional Stage: 2 to 3 weeks

 

Between two and three weeks old, the puppy is going through its transitional stage - lots of things begin to shift as they grow out of total dependence on their mother. 

They no longer resemble little beans that can barely move, but tiny puppies that are independently experiencing the world around them. A big change is that they open their eyes and ears, so they can see and hear who and what’s around them.

Eventually they take their first steps, however small and wobbly - and can move around on their own. 

Socialisation begins as they interact with their brothers and sisters, learning about other dogs and how to behave (with the help of their mum’s discipline!). 

The weaning process also begins from week 3-4, as the carers for the pups feed them on a mixture of mum’s milk with nutritious puppy food - known as ‘puppy mush’. Soon, the pup will eat solid foods only. 

 

The Socialisation Period: 3 to 12 weeks

 

Between one and three months old, socialisation takes a big leap, as the puppy adapts to the presence of both animals and people around them. 

It offers a lot of social and behavioural benefits if your pup’s played with their brothers and sisters a lot from birth -  they’ll have confidence, yet know that they should play gently. 

This is a highly playful and curious stage, and puppies are often frightened and very impressionable, just like human children - but this is key to learning. Having positive experiences with animals and people is vital. They’re learning that they can trust humans and bond with them.

For this reason, it’s the perfect time to start with basic training, like ‘Sit’, ‘Stay’ and ‘Come’. Puppy treats to help with this should be fine, as puppies are usually completely weaned to solid foods from 6-8 weeks old. 

8 weeks old is usually when a puppy’s ready to move in with human owners, as they start their independent life as a young pooch. Socialisation continues in the new home, and owners should expose their puppy to the world around them in a calm and confident manner.

The Juvenile Period: 3 to 6 months

 

You now have a bounding, energetic puppy around the place who’s likely dominating your days! 

Your pup is still growing rapidly, going through fast stages of development and gaining continuously in size, weight - and energy!

At this point, your pup’s pushing their luck in all kinds of ways, so routine, training and discipline is crucial in having them feel calm and safe. Puppy training classes are a great idea, as you can teach them to come to your side on command, walk politely on a lead, play fetch and behave when greeting visitors and other dogs. 

Go heavy on the treats! Reward your puppy any time they obey you, or are calm and polite. This can include times they’re settled on the floor, or when they walk quietly past another dog. This sort of positive reinforcement training helps your pup understand how you want them to act.

Your pup will go on their first walks outside in the world, so walking past unfamiliar dogs will be a daily occurrence and something they should feel comfortable with. 

It’s usual at this age for your pup to bite lots and test how far they can go with it. They’re exploring the world, and are also teething. Training and discipline should also teach bite inhibition, so they know not to bite when startled, and if they do, they won’t bite too hard. 

Routine’s absolutely necessary for a juvenile puppy - they should have set bedtimes, feeding times, and walkies. You may feel cruel keeping your puppy so regimented, but don’t! Dogs respond to structure and will behave in a much calmer, secure manner when they know what to expect throughout the day. 


The Adolescent Period: 6 to 18 Months

 

Dogs go through developmental stages much faster than humans (you may have realised!) so by 6 months old, they’ve already reached what’s essentially the onset of puberty. 

For smaller breeds, they’ll reach sexual maturity from around 6-9 months, for large breeds it usually occurs between 12 and 18 months. 

Females will experience their first heat cycle (like a period) and you may see a small amount of blood on their blankets. Males start to become friskier (!) and show more dominant behaviours such as marking their territory and mounting females more often.

At this point, you might consider spaying or neutering your pup to avoid unwanted litters. The ideal age depends on the individual and their breed, and more in depth information can be found here.

Just like human teenagers, your pup’s behaviour may become more challenging at this stage, and training doesn’t work as quickly. Your pooch might be destructive, harder to manage and bark more often, and they might ignore previously learnt commands. 

Don’t give up! Get some help from your vet or dog trainer if you’re finding your pup more of a handful around now. Keeping them on a nutritious diet, alongside some calming dog treats will also help.

Remember, this stage will eventually settle as your pooch becomes a fully grown adult dog - and you’ll look back on this crazy puppy time with nostalgia. 

FAQs

At what stage are puppies most difficult?

The ‘adolescent’ stage is usually the most challenging. Your previously well-behaved puppy might be more destructive, harder to handle and may bark more often. This is a normal stage for a pup, very similar to the teenage years for humans. Speak to your vet or a dog trainer if you need support; soon your puppy will settle into adulthood and be easier to deal with!

What to expect at each puppy stage?

Each puppy stage produces new developments, caring techniques and challenges for new dog owners. You’ll need to feed your puppy the right foods, comfort them, socialise them and train them as they grow. Articles such as this one can help you learn what to expect at each puppy stage (read above).

What age do dogs get out of the puppy stage?

Puppies move out of the latter puppy stage (adolescence) between 6 and 18 months old. This is variable, depending on their breed - smaller breeds of dogs may be fully mature by 12 months, while larger breeds usually reach adulthood when they’re closer to 2 years old.

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