1 12 year old boxer is being aggressive

Question
We purchased a boxer for our granddauhter but she is unable to keep her now (the dog was free to roam the backyard and chewed up trees, plants etc).  We have taken the boxer in to live with us.  We have a 2 year old lab and an 8 year old shitzu.  The Boxer seems very jealous of the Shitzu and has attacked her twice.  We love the boxer but fear for the shitzu.  I have seperated them whenever I am gone. The shitzu is friendly with people who come into our home if they ignore her but if someone walks up to her excitedly she will jump on them and try to bite them.  We are thinking we may need to surrender her to the rescue, but we have fallen in love with her.  I just don't know if she can live with our Shitzu.  Thanks for any help you can give us.

Answer
Hi Susan,

I'm not sure how long you've had the Boxer; a large part of this may just be the dogs figuring out their place in the new pack order.  (Especially if there haven't been any injuires to the Shih Tzu.)  It also sounds as if the Boxer hasn't had much if any training - that combined with her age makes for a challenging situation, even if she were an only dog!

I would suggest you start implementing the Nothing In Life Is Free program - definitely for the Boxer, and potentially for the other dogs.  The NILIF program is a way to be fair, firm, and consistent in enforcing guidelines for appropriate behavior, and in establishing your role as the person who sets those guidelines.  
http://www.goof.com/~pmurphy/NILIF.html

I would also suggest you read Patricia McConnell and Karen London's book, "Feeling Outnumbered", which has excellent information and a program for managing multiple-dog households.  Patricia McConnell's website is http://www.dogsbestfriendtraining.com/index.php

You mention the Shih Tzu jumping up and trying to bite people - but did you mean the Boxer there?  Jumping up is a common Boxer trait; actual biting is not but some dogs will grab at clothes, or nip at a chin or nose.  The NILIF program will help in general, you can also work specifically on the jumping by focusing on what you want her to do instead (sitting to greet new people is generally not a bad 'default' behavior' to teach) and asking people to ignore her unless she's calm (sometimes it's harder to train the guests than the dogs!).  

If you think the biting is truly aggressive, or if the Shih Tzu has needed medical care from the attacks, this is a more serious issue.  My first recommendations are to have a veterinary workup to be sure there is no underlying physical cause, and then contact a behaviorist who can evaluate the situation and help you manage or modify your dog's behavior.  There are behaviorist directories on these sites: http://www.dacvb.org/about_us/diplomates_copy_1/
http://www.iaabc.org/consultant_locator_dogs.htm
http://www.animalbehavior.org/Applied/CAAB_directory.html

You may be able to get referrals from the rescue group, as well.  There is also a book called "Aggression in Dogs" by Brenda Aloff that might be helpful; Brenda's site is here for a little bit of information about her and the book:
http://brendaaloff.com/

(Both books mentioned are also available at www.dogwise.com and other online book sellers.)

Good luck!

~Jennifer