Puppies begin to go through different stages of development immediately after they are born. The first twelve weeks of their life has many different stages in it, and then they have more stages during the first year. However, the first twelve weeks has the most changes in it for the puppy. The rate that puppies develop depends largely on their breed. Smaller dogs will mature much faster than bigger dogs. Some of the larger breeds of dogs will not fully mature until they are two years old.
When puppies are born, they are deaf, blind, have no teeth, cannot regulate their own temperature, or even go potty. Puppies rely on their brothers, sisters, and mothers for warmth. Puppies do however have a sense of smell from birth, and they use that to find their mother and eat. Newborn puppies sleep about 90% of the day, and spend the other 10% nursing on their mother.
Weeks 2-4 are a new stage in the development of a puppy. They become able to use their eyes and ears during this time. They can usually stand up around 15 days old and walk around 21 days old. Around three weeks old, they become less dependent on their mother and more so on themselves. They begin to play around with their littermates.
At around 5-6 weeks old, puppies cut their teeth. They are able to control themselves to go to the bathroom and start to get away from where they eat to go potty. They also start to ween themselves from their mother and begin to eat hard food.
The next period that puppies enter into is up to 12 weeks old. Puppies are often afraid at this time, they are not very curious. Pet owners need to make certain their dog is getting proper socialization during this time. Puppies start to eat only on their own and at this time they move to their new house away from their mom and littlermates.
After these stages, puppies will go through a few more during their first year. None quite as big as the ones they go through in the first 12 weeks. Most of the next phases are about their social interaction and training. many will reach full size after the first year, but larger breeds often do not until they are two years old.