5 year old Shepherd Mix suddenly aggressive.

[Aggression]

I've owned my White German Shepherd mix since she was 8 weeks old. When she was 2 we had to give her over to some friends to watch because my mom got deathly ill (I'm 15 years old currently). They then didn't want to give her back to us a year later, and a fight broke out, which I eventually won and took her back. I found out later that they would hit her with a stick anytime she was "bad". I retrieved her when she was 3 and a half.
She is now 5 years old (this March) and we have recently moved to Chicago. And within the last 2 months, my dog (Angel) has attempted to bite 4 people, and many dogs.With people, she stands there placidly while they pet her, wagging her tail at a slower and slower rate, and then snarls and barks ferociously while snapping at them. She hasn't bitten anyone, but she's come close all four times. I'm worried. My year old niece is going to be around this dog alot, and although Angel has never snapped at her, I'm still worried.
And when it comes to other dogs, she lunges at the end of her leash, barking horribly and snapping. If she gets close to a dog, she sniffs them for a while, her hackles up and then attempts to bite them (thank god for quick reflexes).
Is there a reason for this sudden aggression towards people and dogs. For those previous 4 years she was a complete sweetheart. And she's never shown aggression towards me or any of my family members, and only occasionaly towards dogs.

Liz

[Dax]

First rule out any medical conditions like thyroid, etc. that can be causing her to feel unwell and cranky. Then you have to look at "why" she reacts the way she does. Dog aggression is normally a sign that the dog was not properly socialized or was traumatized and feel defensive. Most dogs become less tolerant of puppy behavior as they age. That is to be expected.

The people intolerance needs to be addressed with training and caution. No matter what - do not leave any child under 16 with this dog unsupervised. I'd be more interested in hearing about some of her other behavior (food aggression, sleeping)

[Aggression]

I'm taking her to the vet in a week to get her checked for worms and get her vacinations updated. I'll get her checked then. Luckily, It's just me and my mom who live in the house with her, and when my niece come to visit (since the first time she tried to bite someone) I've always put her in my room. Same with other company. I also have an evaluation with a trainer on Febuary 2nd.
She has absolutely no food aggression. At least not with me. I can take away her food, and even play with it while she's eating. Sleeping? Do you you mean is she getting enough sleep?

Edit- And all the people she has tried to bite were just petting her. Not bouncing around or anything, just very calmly petting her back or her neck.

[GretaJack]

My first thought is that the move has upset her. Moving can be extremely stressful to dogs and can cause abnormal behavior from them but it has been about 10 months since you moved. She should have settled in by now. My second thought is to tell you to take her to the vet and have her checked, a normal physical as well as a blood panel. There might be something physically wrong with her that is causing her to feel uncomfortable and, therefore, agressive.

The four people that she has tried to bite, has she ever met them before or were they complete strangers? How do they greet her? Standing over her making eye contact or in a more submissive, hand extended, standing up straight but no eye contact?

Some dogs will bark and even show teeth at another dog when out for a walk on a leash. It could go back to the fight or flight response. A dog on a leash can not run away so it decides to bully up right away.

But no matter what seems to be going on, I would recommend a vet check and investing in a muzzle. If you know what triggers your dog to become aggressive, a muzzle is going to protect you against any liability and protect your dog from the unavoidable fate if she bites or attacks.

[GretaJack]

Slow posting today. Sorry.

[Aggression]

No, she had never met the people before, and 3 out of four were bending down or crouched on the ground petting her. I think if she really wanted to bite them she could have because their faces were definately within range. We moved about 5 months ago actually, and she seemed to adjust pretty well, but I wouldn't be surprised if she was stressed.
The response about the dogs makes sense too.
I am going to get a muzzle, it's just difficult to convince my mom that it's a good thing to do (I don't have an income yet)

[Dax]

Aggression

When she is sleeping does she allow you to wake her, move her, in general pester her or does she respond with a deep threatening growl that says she will bite you if you don't back off.

My first guess would be a combination of advancing years and thyroid (vet should check). Patience for things just isn't what it was when they were younger. Once she has been checked out and healthy you need to work with her to give her correct behaviors. A good down/stay or sit/stay will help lots. I would avoid having people pet her - let her decide if she wants to be touched by strangers.

[AussiesCollies]

I agree with Dax. I have a German Shepherd mix also, and she has never been fond of strangers or strange dogs either. She almost always tries to avoid new people and can be very agressive towards other dogs. But she loves my family and my Border Collie. I think it's a common trait with certain breeds to be a bit more agressive towards strange things, but definitely get her completely checked out by the vet. Does the dog have any basic training? As in sit, stay, down?

[jennifer B]

We have a male german shepherd who will be 4 in March. When he was a year and a half old he went into kidney failure and we were told he only had one (small) football size kidney and was given two weeks to live. We prayed hard for that innocent boy and spoiled him rotten for those two weeks which turned into months and then years.... but, during the time of not knowing whether he was going to live or die he became aggressive. He started growling at visitors and nipped at a frinds little girl who was near his food. He has progressivly gotten worse and growls at me and other family members. He has never bitten any of us and I know his illness is what has caused the problemsbut, do we take a chance that it may go further than growling tward us? He is always in his inside kennel when we have visitors so I'm not concerned about other people. It is our 14 year old sons dog and he is not aggressive tward him. Any advice? He (Caleb) does have kidney problems a few times per year where he really is not feeling well.

[Dax]

Jennifer

It is great to hear that he survived these bouts of Kidney problems. Have you spoken to your vet about the aggression? He may have some meds that might ease the discomfort.

I would not allow the growling especially to family members. He might think it’s ok to do because he’s under the weather but he might take it into his head that he’s the boss.

I would strongly suggest contacting a behaviorist to access the situation. My local SPCA has a one on staff. Your local humane society might also have one or your vet could recommend some one