Dear Lisa: I have two Yorkshire Terriers that are 4 months, 1 week old. I was wondering when they will be considered adults. They weigh 5 pounds 4 ounces, and 5 pounds 6 ounces, respectively. I'm also wondering when they will stop growing. They still have their baby teeth, but the vet tells me anytime they will start losing them. --Prolonged Puppyhood
The American Kennel Club considers any breed of dog to be an adult at 12 months of age. This is based on the dog show rules for puppies. However, each breed and even individual dogs of the same breed can vary as to when they "mature" past that playful puppy stage. When their teeth fall out isn't a real indication of adulthood as their "adult" teeth should come in way before their first birthday.
A general rule of thumb I found in my experience across many breeds that dogs tend to "settle" into their adult behavior around 2-years-old. A way to facilitate this is to enroll your puppies into basic obedience classes and teach them the proper behavior that you expect of them. By you taking charge and giving them the direction they need, they will develop and grow into wonderful, well-mannered adult dogs.
As for their size, again generally, dogs grow in height until around 10-months-old or so and then begin to fill-out in muscle and bone structure until 2-years-old. But most dogs reach their "adult" weight around 12-months-old. The Yorkshire Terrier standard expects adult dogs to weigh no more than 7 pounds. So far, your dogs seem to be of correct weight. Just be sure not to overfed them or give them too many treats that might lead to overweight adults.
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