Why are all of the sudden in the last 2 weeks are my 2 female labs barking and growling at each other? They are showing teeth and bark non-stop until someone stops it. They are sisters and have been together since birth. They are now 9 years old. FYI... we did get a new male puppy about a month ago. But the 2 labs do not bark or growl at the puppy.

Thanks!:)

Is one of them possibly coming into season?

Sorry forgot to mention... they are all fixed

Fixed or not, the male has destabilized their relationship. Nine years is awfully late for such a rivalry to break out, but the male may be enough. I don't know if better leadership on your part now will be enough or not. The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at Raising Your Dog with the Monks of New Skete (http://www.dogsbestfriend.com/) For more on being top dog, see Establishing and Keeping Alpha Position, Letting your dog know you are the boss (http://www.dogbreedinfo.com./topdogrules.htm)