Depending on who you talk to however, there may be a variety of opinions on what actually occurs during the early phases of a canine's life.
It is safe to say that the time frames given regarding development are approximations, since Shetland Sheepdogs each change at their own rate.
These critical periods of social development (and they are critical in their final maturation) are:
Puppy Development: Birth - 2 Weeks Old
As discussed in the Super Puppy Exercise page, pups handled now grow faster, mature faster and are more resistant to diseases.
2 - 3 Weeks Old
Eyes and ears begin to open up. Development can now include these other senses.
3 - 5 Weeks Old
This is the beginning of the socialization period. It is when canines learn to be dogs by playing with each other. It includes learning the body language, reading and performing the behaviors that communicate non-verbally.
Removing a pup too soon from its litter prevents him from experiencing these necessary milestones.
Part of the puppy development is to learn to associate and bond with people.
Studies show that a fear response begins now and escalates until leveling off at week 10. A canine must be introduced to humans now as part of their puppy development or the opportunity is lost forever.
That’s where the idea arises, that the pup needs to be brought home by 7 weeks; in case the breeder wasn’t conscientious about ongoing contact with the pups before then.
So, find out if the breeder interacts with the pups each day, and avoid pet store pups who have come from situations where the pup was in relative isolation during the first 2 months of life.
In spite of this fear period continuing, it is the best time for new owners to continue socialization with introductions to new places, people and things to expand his experience as much as possible without sending his fear response through the roof.
It is also the time when many new owners are concerned about the the unvaccinated dog. But it is my opinion that the socialization activities are more important than protection from the slim possibility of exposure to disease.
That is because, after this time period, while additional behaviors can be learned, it is more difficult. So get them out in the real world before that window of opportunity closes.
As far as bonding with humans, I remember years ago being told that if puppies were not separated from their littermates by week 9, they would bond with each other but not to a human.
This is why there was the philosophy that one should not raise two puppies together at the same time and why some breeders sell early.
I have since seen with my own pups that this is not true as long as in addition to canine interaction there is human interaction as well.
Generally speaking, this is when sexual maturity and adult behaviors become part of the makeup.
This is also when assertive or submissive traits will show make themselves evident.
If you are purchasing a Yankee Sheltie pup, you can be assured that the initial work of socialization with dogs as well as human exposure has been maintained until you take him home.
My hope is that the socialization will continue with the new owners in a gentle manner to allow every Sheltie to develop his potential fully.
So there you have puppy development in a nutshell.