...i would have to say rocky acts like so while on his leash during walks.
Do you happen to know anyone else that has a good natured and confident adult dog (i.e. one that is well socialised, and neither a bully nor submissive), that might be willing to have your guy around to play? The reason I ask is because you may actually be dealing with leash aggression, rather than dog aggression.
Dogs are actually the MOST likely to display aggression when on a leash. The reason for this (in simplistic terms only - reality is probably much more complex) is thought to be for two main reasons:
(1) When they're on a leash, the normal fight versus flight decisions any dog (or person, for that matter!) makes are not possible. The dog
cannot choose to flee if he feels threatened, so the only option available is fight. Hence the aggressive reaction.
(2) Dogs normal body language - signals to other dogs - are restricted when they're leashed. They're not able to give a full range of "I'm friendly, not a threat" or other deferential / polite (in dog terms) signals to approaching dogs or those they're approaching. A great deal more miscommunication then occurs in the first place.
In short - you end with a situation where it is NOT clear to the dogs whether or not they're friendly, and the dog doesn't have the option of running away or distancing himself if he's unsure. End result is not surprising once you realise this - which is that a heck of a lot more aggressive responses occur when one or both dogs are leashed.
I suspect that may well be the problem in your guy's case. You would need to see how he is off leash with other dogs to know for sure though. This is best tested in a controlled environment (NOT a dog park), where there is only one other dog to deal with, and that dog is well socialised and balanced. Better that it's off your own dog's turf too (so not your own backyard).
If you find that he's able to socialise in an off-leash environment, then I'd suggest two things:
(1) Get yourself a trainer or behaviourist to help you work on diminishing his leash aggression. This takes time and work, but generally can be done.
(2) Continue to socialise your dog off-leash, in controlled circumstances. I wouldn't suggest a dog park, where you have no control over which or how many dogs are present, as suitable. Or at least not for some time yet - he needs to be well socialised himself, with confidence built up, before facing that sort of stressful environment (imagine the damage that would be done to his confidence if he were attacked, for example).
On jumping - I suggest a search of the forums, and a separate thread if needed. There are many many threads about how to discourage jumping behaviour. Generally the solution revolves around turning away and ignoring the dog (so he isn't rewarded by gaining your attention - which is what he's after), and teaching the dog a more polite way of seeking your attention instead (which you should always reward with attention).
