Thanks for the additional information, it is helpful. Dogs are aggressive toward people for a variety of reasons. It might be that they are fearful of people and thus are aggressive before the person can be. In other cases, a dog is aggressive in order to dominate the people. Other causes could be that the dog feels they are the alpha member of the pack and as the alpha member they must protect the pack (you or the kids) from threats (people). So it may be that your dog saw your husband as a threat to the children and reacted.
Owners sometimes make the situation even worse by tensing up and worrying about what will happen. The dog senses the owner worry and feels that he is justified in his aggressive stance because you are obviously worried about the people. They don't know you are worried about them attacking, they just feel that you are worried and assume it is the people. If you were a little worried about your husband yelling at the kids then that may have contributed as well. So you and your husband have to try not to be worried about his possible reaction in the future.
One way of stopping the behavior would be for your husband to take total control of him which includes feeding, walking, and giving affection. You would need to step back and let the dog start going to your husband for these things which will help make him submissive to your husband. It does cut back on aggressive behavior toward a spouse if the dog has to depend on them for food.
You will have to gain total control over the dog as will your husband. As the alpha it would be your job to protect the kids, not the dogs so he shouldn't growl at your husband. You will need to have him obedience trained. If you can, I would do group classes with both your husband and you participating in the daily training practice sessions. I would also have any older children (4 and up) also participate. The following site is helpful to teach you how to train your dog. You can then start before classes start.. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
Now the dog will still protect you if something should happen because you will be protecting yourself and as part of the pack, he will follow your lead and protect as well. But if you are calm around someone, he will see that you are ok and there is no need to help. This is why being the alpha member works well.
You will also want to keep a leash on him at all times initially to grab if he should disobey. I think you will be pleasantly surprised at how well your dog does with training. Dogs like knowing what is expected of them and they love the little paper thin slices of hotdogs that I use for treats while training. Give this a try and see how it works for you.
Since this just started, I think you can get it under control pretty quickly. Male dogs frequently challenge their owners with a growl around this age and if they are not quickly brought under control, it does tend to get worse, so be sure to get that obedience training started as soon as possible.
I'd stop letting him on the furniture as well. Dogs that are allowed on furniture tend to feel that since they are at your level, they mentally feel elevated as well in the pack order and thus are the boss. Keeping them on the floor can help lower them mentally back to a submissive position in the pack. So the first thing is to not allow him higher that the humans or even on the same level. Keep a leash attached to him and you can use corrections in the form of short tugs on a leash and firm low toned "NO" to help stop unwanted behavior such as jumping on the couch.
In addition, if the situation is not improving using the techniques I describe, you may have to consult a professional behaviorist. You can usually find a behaviorist by asking your Vet for a recommendation or you may be able to find one using the following site.
I almost forgot to mention medical causes though I don't thing they are to blame. You can read about these here:
Unfortunately, the site does not allow me to make clickable links, so to view the supporting websites, you will need to copy and paste the link into a new browser window or tab.
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