9 month old puppy showed aggression to another dog this morning

[drivinmecrazy]

We have a (almost) nine month old Weimaraner puppy.
This morning while on our walk we met another pup we'd met before.
As we approached he showed his normal behaviour but when they met my pup literally showed his teeth and quite aggressively approached the dog.
Luckily we were on a part of our walk that they were both on a lead.
I was mortified. We've never seen any aggression signs from our dog.
We have noticed that he's been humping his favourite teddy much more recently so are wondering if this is a 'normal' profession as he matures or something we should worry about.
My mind is veering between thinking that maybe he just didn't like this dog or the other dog showed some cues I'd missed, or wether it's our dog starting true adolescence.
Obviously we won't be getting him nurtured until his a good deal older, but if he's going to repeat this reaction it'll be a struggle.
I guess I'm hoping someone might convince me it was a complete one off.
He's literally never shown any aggression before so it's very out of character

I would start training to ignore other dogs, my dog first started showing signs of reactivity at around the same age, no idea why he was socialised and we did all the normal puppy classes etc.

I wish I'd started training to ignore other dogs from day one tbh. You need to be the fun one and the one he's interested in not other dogs.

Fwiw we waited until my dog was 3yo as per the above advice and I think it did help calm him down. He was only ever reactive to male dogs though so it was def a hormonal type issue.

Our Weimaraner is far more reactive on the lead. She's coming up to 1 now and is getting much better. Don't panic about it too much.

I’m dog training at the moment for this exact problem (entirely diff breed and age to yours) but trainer suggests I loudly AH! And then step in the way. Reward with treat for ignoring the other dog. It will take a lot of effort but apparently it’s doable. We growl at everyone though so a longer road…

Apparently saying ‘No’ or the pets name is just blah blah blah to a dog.
so it has to be a noise they know is different. Also a tone that suggests you aren’t happy.

I would recommend finding a new trainer - the technique you're using means your fit could start associating other dogs with being told off (the stern voice and the AH!) rather than the treat, making the behaviour worse.

Dog's can't be trained to do a No or an Ah. They can be trained do something else like look at you for a treat or a game, depending on what your dog finds valuable. Rewarding an absence of a behaviour is tricky as they have to start it to stop it.

A similar example would be my older pup at agility. She used to get really really excited and lunge and bark at the dogs running. So I took her back away to a point where she was looking but not doing and then rewarded her for laying on a mat until she was offering laying on the mat and then looking at me for a treat. Over a few months we've moved closer to the action and are now phasing down the rewards to one every few minutes. She still runs like a demon and gets revved up when it's her turn but she's no longer overstimulated throttling herself at the side of the venue and WANTS to lay down and just be between runs as it means magical bits of pate appear. You need to do the same with meeting dogs. Keep to a non reactive distance and reward for looking at you. Then move closer. If you meet and can't control the distance then treat in the face and keep on walking!

http://www.clickertraining.com/reducing-leash-reactivity-the-engage-disengage-game

Ah we use this. Not a clicker but a ‘spotted the threat’ big overreacted YES. Walk on by, treat for ignoring.
Its the ones we miss, round a corner for example where she flies off and then ignores me completely until I have to pull her away (she’s tiny).
We are on our third dog trainer now..

But not the OPs issue and I won’t take up any more thread.
Good luck with your dog OP. Hope it was just a one off..

Think of it less as a treat for ignoring and more as a treat for disengaging with the scary thing and engaging with you instead. Part of the reason it's so effective is that it teaches them self interruption if done right - almost like the canine equivalent of a deep breath. If she is reactive off the lead you need to keep her on lead so you can control every interaction as best you can. Dogs that practice things get very good at it. Mine used to be a frustrated greeter and we used the click the trigger method with great success and nipped it in the bud pretty quickly. I don't use a clicker out and about - I use a marker word.

Thanks @Newpeep very helpful. And will certainly give this method more time.
No, never off lead. But just when we round a corner etc.

Thank you to the posters that have shared their knowledge.
I've learnt so much. Every day is a learning day !
We've had two successful walks since so 🤞 it was a one off.
Most negative behaviour our dog has shown has usually been more about us getting complacent rather than him.
I've gone back to using far more of 'look at me' to bring his focus back.
We take a quarter of his daily meals out with us so we do so much reinforcing but it's easy to forget when we have a few good days.
He's so young really, even though he's the size of a horse!!