4 months puppy aggression towards other dogs

[Daniels]

Hi! This is my first post!

 

I'm Daniel, and 2 months ago, my wife and me got a BC. Her name is Ellie. She is a great pet dog. We don't have her as a working dog, but I think we give her exercise enough.

 

She has some problems with other dogs(not with people, fortunately) when there is something like a toy/stick/food present(very often at parks), she is great with them otherwise.

 

My ritual several times per day is like this:

I go to the park with a short leash. I look for other dogs so she can play with them. If I find dogs she is happy to play with and they have a great time(unless they find a stick during that play).

 

After this, we start our fetching time. I left my backpack on the ground and I switch the short leash for a 50 feet long leash. At the moment I change the leash and leave my backpack on the ground she is obsessively focused in playing fetching and doesn't care about other dogs.

 

This means other dogs can be at 5 feet of us and she wound't care about them. But if any other dog approach the backpack or her toy she gets really angry and tries to bite them. Sometimes she even goes to say hello to them in a friendly way with the toy in her mouth, then she leaves the toy on the ground and her friendliness changes suddenly in aggressiveness. If she keeps the toy in her mouth she just tries to play with the other dog chasing her.

 

This gets worse if the other dog is smaller than her or too shy or too friendly to be aggressive. If the other dog gets angry too and respond to her with aggressiveness, she instantly gets scare and submissive.

 

She is still pretty inoffensive, since she is 4 months old(19 lb.). But this behavior is pretty recent and seems to be getting stronger.

 

She is great with people, though. We can take away her bowl full of food and she wound't complaining at all. When we play tug she releases the toy at the moment I say "drop". She knows some commands: sit, down, paw.

 

She doesn't have her toys all the time at home. We take them all when she is not playing except for a chewing antler.

 

What do you think I should do about this?

It's really annoying when she gets that mad. It lasts about 10 minutes to get her settle and being friendly again after this incidents. And I'm worried about when she gets bigger.

I have some other questions that I will share in other posts.

Thanks!

[GentleLake]

I'd get her into a good socialization class with a good positive reinforcement trainer ASAP. She may be beyond the age for a puppy class -- many end at 16 weeks -- but even a good introductory manners class should be helpful.