Weight Loss/Behavior change

Weight loss/behavior change German Shepherd 2 (3 in October) Neutered (cryptorchid) 80 lbs. (was 90 a few months ago) Always been a high energy, high anxiety dog. No medical concerns or issues before recently. He has lost weight in the past few months. Recently, in the last two weeks, he has started showing random aggression towards our other dog. They are best friends and NEVER had any problems. August 29, out of no where he started snarling, showing teeth, and growling at her. We had to separate them for a bit and then they were fine. Again today, he has done the same thing. However today, it has been multiple times. Each time has been for no reason and nothing provoked it. They were both laying down and he jumped up and got aggressive with her for no reason. We have them separated now. He hasn’t gotten aggressive with us. Any idea?? Please help. This is not our dog normally.

Hello!  So you have a GSD, nearly 3, recent behaviour change / aggression / anxiety, weight loss, I'm going to assume a good eater (as in, not incredibly picky / off food.  Correct me if I'm wrong about that;  it changes things). Dog : dog aggression can be classified neatly into issues between pack members and issues with strangers.  Dogs always have a pecking order within their pack and if nothing external has changed, something internal may have done; maybe the roles are subtly changing, or perhaps there is illness making the previous 'pack leader' (it's more complicated than that) weaker?   Anyone can call themselves a behaviourist but there are some good evidence-based veterinary behaviourists.  Please remember that just because you didn't see a reason, doesn't mean that the dog didn't have one from their point of view and a behaviourist could help you to nail it. However I think that you, your vet and the behaviourists may feel that it's a good idea to start by finding or ruling out (as far as you can) underlying illness in this case. Perhaps they can help you to fathom out whether your dog is definitely a neutered cryptorchid, as in: have you or they seen the veterinary notes or spoken to the person who took the internal testicle away?  If not, you may ask to establish that it isn't still in the abdomen somewhere.  Abdominal testes can cause real problems and be extremely hard to locate but can also cause cancer. Other causes of weight loss and 'stressiness' may include hyperthyroidism (rare in dogs), other underlying disease (diabetes, goes with drinking lots normally etc), cancer (again - internal testicular??), pain (hips?) and so on. It sounds as though your vet may have their work cut out and is definitely worth seeking their advice as soon as you can. I hope that some of this helped!   Try searching for internal testicle (or cryptorchid) in the blog.

I'm not a vet, but I can offer some general suggestions. Sudden behavior changes in pets can be concerning. Since you mentioned there are no medical concerns, it might be worth considering consulting with a professional animal behaviorist or trainer.

They could help identify the root cause of your German Shepherd's aggression. In the meantime, keeping them separated when you can't supervise might be a good idea to ensure everyone's safety. And yes, I've heard about the best CBD oil for dogs with anxiety https://www.orlandomagazine.com/best-cbd-oil-for-dogs/ , so that's something you could discuss with your vet.

They could help identify the root cause of your German Shepherd's aggression. In the meantime, keeping them separated when you can't supervise might be a good idea to ensure everyone's safety. And yes, I've heard about the best CBD oil for dogs with anxiety(https://www.orlandomagazine.com/best-cbd-oil-for-dogs/), so that's something you could discuss with your vet.