Why does my dog growl and snap when petted after getting a new dog?

Before assuming this is a behavior issue, I would want to rule out a possible medical issue first. When I hear about sudden changes resulting in aggressiveness, the possibility of pain or discomfort in one of the dogs could be the root of the problem. When a dog is not feeling well, it is only natural for it to react in a negative way if one of its buddies is trying to get it to act normally. A thorough physical exam should be performed by a veterinarian in order to rule out any sort of orthopedic or neurologic pain. Thyroid conditions can also be responsible for behavior changes as well. If it turns out that no medical issue can be be identified, you will have to start considering what may have started this sudden change of heart by Mill. You will have to think back to when it started, when the problem occurs most, where it occurs most, who is around when it is occurring, who ISN'T around when it is occurring, so on and so forth. These types of issues can be long and complicated to resolve, but usually as soon as the issue is identified the road forward becomes much easier.

This behavior is likely to improve with time. Take them on leash walks together frequently (twice a day if at all possible). Feed them in separate rooms, as this is the time he is most likely to actually snap at her. If his behavior is not improving, consider keeping a [basket muzzle](https://www.petco.com/shop/en/petcostore/product/baskerville-ultra-black-muzzle-for-dogs) on him when they are inside so he can't hurt her. Also, if his behavior isn't getting better, ask your vet for a referral to a trainer or behaviorist who can help you. Thanks for asking PetCoach!

It sounds like Buddy is giving the proper signals to the new dog that things are a bit too much for him. If he is showing teeth or growling that means he's had enough and the play session between both dogs should end before one or both dogs escalates the encounter. Short, supervised sessions are best and if either dog shows they've had enough, separate the two into other rooms or crates for a while before trying again. You may also want to pick up any bedding or toys/treats that may be fought over. Since Buddy seems pretty stressed out by the situation, creating a space that is just for him such as a bedroom with his bedding, food, water, etc is best so he has a place where he can get away from the other people and dogs and relax on his own for a while.

I'm sorry to hear that you're having this issues! It sounds like there are a few different things going on here with both dogs, which definitely makes the situation more complicated. From your description, I can't quite tell if your male dog's crate aggression issues are directed at the puppy only, or if this is more of a general problem and he also snarls and runs from the puppy at other times as well. This is important information to help determine what may be going on so that we can make suggestions. I'm not sure how old your new puppy is, but if she is younger than six months, aggression at this age is quite uncommon and very concerning. Possessive aggression (also called resource guarding) over owners is a relatively common problem that can often be successfully treated, but you would really need an expert who can help you in person. Particularly in a young puppy, a veterinary behaviorist would be your best bet to evaluate the pup and put together a detailed plan to start working on this problem ASAP. If you want to keep both dogs, this will definitely require some professional assistance and quite a bit of time and effort for training. I would recommend asking your veterinarian to refer you to a board-certified veterinary behaviorist for some hands-on guidance.

I'm sorry to hear that things aren't going well with your new dog. Unfortunately, it sounds like this may not be a good match - just like humans, some dogs have very different personalities and may simply not get along. If you want to try keeping both dogs, I would really recommend getting in touch with a veterinary behaviorist who can evaluate the dogs in person to give you a better idea of whether this is a fixable issue - if so, he/she can help you put together a detailed step-by-step plan to work on the problem. You can search for a behaviorist in your area here: www.dacvb.org In the meantime, I would recommend keeping your older dog on a leash or physically separated from the other dog with a baby gate or other barrier. This will allow the younger dog to relax a bit without being harassed. If things go well like this for a few days, you can gradually allow short periods of contact between them. Reward both dogs when they are together, and particularly praise and reward your older dog for calm behavior around the new dog. You may also want to try a DAP pheromone collar on both dogs, along with a natural calming supplement such as Zylkene or Composure for your older dog to see if this helps a bit.

it is important to remember that Chico was there first, and is used to a certain level of attention from you. This newcomer has no expectations, so be sure to dote on Chico as much as ever so he feels secure. Then, gradually, you can increase the amount of time you give the new guy (without taking anything away from Chico). The second issue you are facing is that the dogs have to sort out, for themselves, who's who at the zoo. In other words, they may have one order of inportance to you, but they need to determine amongst themselves who's top dog, who's in the middle, and who's on the bottom. There may be a bit of snapping and barking going on, but as long as there are no injuries or serious fighting, leave them to it. Once they get it squared away, everyone will know his place in the pecking order and will (usually) behave accordingly.

If this is a sudden or new behavior that happened out of the blue, and Toby is now biting and snapping when picked up or handled, I would be concerned that there is something going on such as pain or illness. Often times, a sudden behavioral change can indicate pain or another underlying condition. A good first step is to schedule an appointment with your vet to rule out any health issues that could be causing this. If Toby checks out healthy and he is still acting aggressive and trying to bite you or other animals, I would seek out the help of a trainer or veterinary behaviorist in person. Aggression is a very serious and complex issue and having someone there in person that can observe, assist and provide a tailored plan to help change Toby's behavior is best. Veterinary behaviorists are great as they are able to prescribe any needed medication in addition to a training routine to help create a safer, stress-free environment. You can visit this site to learn more about veterinary behaviorists and find one in your area: http://www.dacvb.org/about/member-directory/