Dogs do not go from being puppies to adults.. They experience being teenagers, just like humans. They shouldn't be considered "bad dogs." They are just going through a growth phase. For most dogs, this happens between the ages of about 6 months to 2 years.
A primary reason for abandoning dogs in shelters is behavioral! And unfortunately, many returned dogs become euthanized. Exercising some loving patience is absolutely essential.
Signs your dog may exhibit as a teenager:
Increasing sensitivity and less self-control. A sound or a movement that used to be familiar is now upsetting.
Ignoring your commands
Climbing on furniture ( "a sign of a vestibular system challenging itself")
Showing aggression or fear towards other animals or people
Chewing things (to "lower stress hormone levels")
Expressing new vocalizations
Pooping in the house.
So love your furry friend as they go through their transitional stage, for they will surely become one of the most cherished members of your family!