Not soiling in their bed is just one step, mothers teach their pups. With my pups this usually happens around 4 weeks of age, when they are able to meander out of their whelping bed on their own. There is so much more that mothers teach their pups; how to enteract with each other; within the pack; what the pecking order is within the pack, acceptable behavior. If a breeder is doing their job correctly they are assessing every pup assessing the litter's temperament to better place them in a home enviornment that is best suited for the pup, ensuring that the new family will have an easy transition and both will have a long happy relationship.
Breeders are also training are training pups, grooming, basic commands, interacting with them on a daily basis.
As far as making it more difficult for a pup to leave the breeders home, allowing the pup extra time to mentally mature and given more socialization time a pup can better handle changes at 12 weeks or older than they can at 6, 7, 8, 9 or 10 weeks.
__________________ Mardelin Yorkshire Terriers |