Dog attack only leash dog

[michaelcdf]

Hello,

Here is the situation, my friend dog when in the dog park will play for hours with all the other dogs he is very friendly
BUT when the owner of the other dog put them on leash he will go and attack this dog. (my dog also and they know each other for month)

When his dog is on leash and other dogs are on leash everything is fine.
Doesn t matter if the dog is 1m or 20 meter away as soon as the owner put the leash he go to attack the other dogs.

I don t know how to help him.

Of course all the basic are covered, the walk, the exercise and the affection

What can I do
Thanks in advance for your help

[LeonilCraig]

There are many reasons why your dog may not like being rushed by an off-leash dog when he’s on leash. Off-leash dogs are, obviously, the bane of many of my reactive clients’ existence, but senior dogs; those recovering from surgery, illness, or injuries; shy pups and fearful dogs may also find the attention of off-leash dogs upsetting or overwhelming. Even friendly dogs may not appreciate interacting with another dog in such a socially unequal situation – leashes can cause a lot of issues...Great sources!