Yeah it doesnt matter at the age, they can start whenever. Taya was 8 weeks when she started to Bark. of course that was when i brought her home. so i'm sure she was barking at her breeders house also.
well some breeds of dogs are not known to bark. even though they can. Taya my Papillon RARELY barks. only when she's left alone she'll bark. otherwise she's quiet. my other dog Britt a Springer barks ALL the time at people she doesnt know, or a noise she hears and doesnt knwo what cased it. she'll bark like crazy.
I will have to agree with the others. I think it depends more on the personality of the dog. Lady rarely barks and she is 1 1/2 years old. Copper has barked from day one and so as Addie.