Hi Everyone,  I have a 4 year old male Labradoodle who up into I got another male puppy of the same breed, got on with every dog he ever met.

10 months later he still generally gets on with most dogs but occasionally gets aggressive for no apparent reason. It's normally just A LOT of barking and teeth showing etc, but he did nip a dog this week and I want to try and stop this behaviour from getting worse.

I assume this will be some kind of dominance issue, but I would like to understand why he is doing it and how to try and stop it. 

Both dogs have been neutered.

Any help would be most appreciated!

It could be a second 'fear' stage, or it could be associated with his early neutering (assuming he was done early as your youngster is very young yet) :-( as unfortunately this has been found in some cases to cause issues like this - not dominance, but general aggression as he will be treated 'differently' by dogs.  It may simply be triggered by the newcomer.

Behavioral Considerations
The study that identified a higher incidence of cranial cruciate ligament rupture in spayed or neutered dogs also identified an increased incidence of sexual behaviors in males and females that were neutered early.(5) Further, the study that identified a higher incidence of hip dysplasia in dogs neutered or spayed before 5 1/2 months also showed that early age gonadectomy was associated with an increased incidence of noise phobias and undesirable sexual behaviors.(6) A recent report of the American Kennel Club Canine Health Foundation reported significantly more behavioral problems in spayed and neutered bitches and dogs. The most commonly observed behavioral problem in spayed females was fearful behavior and the most common problem in males was aggression.(12)

from http://www.caninesports.com/SpayNeuter.html

you will need to put in a lot of work to reduce this - I advise methods used by Victoria Stillwell (Its me or the dog), well worth watching a few programmes, you need to reduce the stress and increase confidence

Thanks Penny - I will have to watch that program for some tips.

The older dog was neutered at about a year and until our puppy came along showed absolutely no signs of aggression with dogs or anyone TBH. You couldn't have asked for a better dog.

Is it worth taking them out seperately to try and reduce his stress levels and is there any reason why he only reacts the way to certain dogs?

Sorry. the title of the topic was misleading - sent before I proof read.

It's my 4 year old that is showing this behaviour.
My puppy is big and boistrous and shows absolutely no signs of aggression.

Was your youngster with him when it happened?  What was his role in the contretemps?

My two youngest dogs are similar ages to yours (4 years and 14 months) and I can offer a few different options;

* When you get a new puppy you expect your older dog to take a bit of a back seat whilst you train the newbie.  That's entirely natural and yours are a good distance in age which means that your older dog ought to be secure enough in your affections not to mind, confident enough to manage without a bit of training for a while and mature enough not to regress.  However this isn't always the case and it might be that you've taken your eye off the ball a bit too long.  Go back to some one to one training and get back to a training class if you have a good one near you.  It might help your older dog to remember his training and give the two of you a chance to re bond without the pup nudging in :)

* Interacting with your pup will have given your older dog some additional confidence in doggy play and manners.  However, he might have got used to a more physical way of communicating which is obviously too much for his other dog acquaintances!  A training class will help to reinforce that he can be alongside other dogs without paying them too much attention.  A good trainer will also be able to help you read the signals your lad is giving (to you - "help get me out of here", or to other dogs - "c'mon then let's tumble")

* Dogs that have been neutered are in danger of being 'bothered' by other dogs who can no longer read what they are.   Although this didn't adversely affect your older dog it might be having an affect on your youngster which in turn affects your older dog.  Your pup is probably experiencing changes associated with adolescence too.  Even though you've had him neutered (too soon I think) he's still undergoing changes which might trigger behaviours in your older dog.  I'd recommend doing some reading into neutering to see what your options are.  (My two are entire so I can't really help with this aspect although my 8 yr old is neutered and does get used as a play thing by the other two...)

* Have a read of Patricia McConnell's website - she has some very good training advice and I can heartily recommend her books.

Hope this helps :)

Thank you. The pup is normally there but he has also displayed this behaviour when he's not. At first I thought he was just looking out for his wee bro but Im not sure if that's the case anymore.

When he is off the lead he normally plays with other dogs without any problem - but can "lose it" for no apparent reason.

Ill take your advice and enrol him in some more classes and spend some more one & one time with him without the pup being there.

I will also check out the website you recommend.

Thanks again for your comments as much appreciated :-)