black lab behavior

Question
2 1/2  year old female lab - not spayed.  Have had her since a puppy - has been around family - friendly and loving.  Husband has trained her and is the one person that has spent the most time with her.  She had been going to work with him, up until 9 months ago. She was too aggressive to the public, had to be tied up.  At home she is on good behavior. But, she is aggressive - growler and barker towards unfamiliar people.  Recently she's become agitated/aggressive for no particular reason at family. Has bitten family member - no reason for her to become agitated. The 2nd and 3rd recent incident occurred with husband. She growled/snapped at my husband when he greeted her in the morning. He reprimanded her immediately, and she continued to growl and back-up. She came to me afterwards, I guess for motherly comfort - she was shaking.  Seems like something psycho is going on.  Took her to the vet for check-up thinking that her eye sight was a problem and she didn't realize that it was him. check up came out fine. Vet's suggestion was to spay her.  This is new behavior and we don't know what the cause could be. Very sporadic and unpredictable agressiveness. BiPolar behavior?  We've had 3 other labs and have never experienced this sudden agressive personality.  Appreciate the help. We are concerned about leaving our family dog alone with our children and grandma.


Answer
I wholeheartedly back your vet.  She is reaching maturity, and the temperament formed genetically and by early socialization is nearly fully developed.  Such changes are common in a dog's third year.  There is no way a dog with aggressive tendencies should ever be allowed to breed.  Spaying should reduce them plus ensure never passing them on. It also greatly reduces chances of cancer later in life.  

Tie her in the back yard?  That will only make the aggression worse.  See www.dogsdeservebetter.org  What is your plan for the next time she comes in season?  Get her spayed, and then see http://www.dogbreedinfo.com./topdogrules.htm