Why is my 5-year-old dog suddenly aggressive, biting, and attacking?

Oh dear! I'm sorry to hear that you're having this problem with Onyx. Human-directed aggression in dogs is a complex behavior issue that can have many different causes, so I'm afraid it's difficult to say what might be causing this without a full behavior history and an in-person evaluation. This sounds like a very dangerous situation for you, so if you want to keep Onyx, I would strongly recommend making an appointment with a veterinary behaviorist who can evaluate him in person and help you determine what is causing this behavior. Aggression issues like this can be treatable in many cases with careful management and a good training plan to work on the problem, but this should only be attempted with assistance from a trained professional. You can search for a board-certified veterinary behaviorist in your area here: www.dacvb.org

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/

Abrupt changes in behavior like this in dogs is very concerning to me. I would be worried about some underlying neurologic disorder that could be going on. If nothing has changed at home, her routine, or the environment in general, then I would suspect an underlying medical issue. I would recommend taking her to be examined by your veterinarian and possibly having some lab work performed so they can try and determine what is going on. Your vet may recommend further work up by veterinary neurologist or may recommend a behavior modification drugs like Xanax or Prozac. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.

Biting aggressively is a serious concern and a very complicated thing to deal with. Leash aggression can sometimes manifest and be redirected toward the person putting on the leash, however if this suddenly happened out of the blue I'd be concerned. A good first step with any behavioral issues that comes on suddenly is to schedule a vet visit to rule out any issues such as pain or illness. Something wrong such as a slipped disk causing pain in the neck or shoulders may make having Griffy's collar or neck handled painful, causing him to bite. If he checks out healthy, talking with a trainer or behaviorist in person is a good next step. They can work with you on a plan to gradually reintroduce the leash to Griffy through positive experiences (such as giving a treat when you bring out the leash, gradually getting him used to it again, etc) and can observe in person what exactly is going on to better tailor the plan. A veterinary behaviorist can also work on both medical treatment and behavioral treatment at the same time to make things less stressful for both you and Griffy. If he is attempting to break the skin while you put the leash on, refraining from doing so until you've talked to a trainer or behaviorist in person is best. You can find a list of local behaviorists in your area by checking out this link: http://www.dacvb.org/about/member-directory/

I'm sorry to hear Cooper has been acting this way. If this behavior is sudden and new, a good first step is to schedule a visit with your veterinarian. In some cases, underlying pain or illness can cause a dog to change behavior and suddenly lash out when otherwise they were sweet or friendly. Your vet can help determine if this may be the case. If Cooper checks out healthy, I then recommend talking with a trainer or veterinary behaviorist in person as aggression toward people is a very complex and serious issue which requires professional help in person. You can learn more about veterinary behaviorists and find one in your area with this link: https://www.dacvb.org/page/about

I'm sorry to hear that you're having this problem! If this has been a fairly sudden behavior change for Elsa, the first thing I would suggest would be to have her examined by a vet to see if there may be a medial reason for the aggression - many illnesses including thyroid problems and neurologic issues can cause sudden mood swings and behavior changes like this, as well as anything that may be painful such as an injury of some kind, arthritis, etc. If your vet determines that Elsa is healthy, then I would strongly recommend making an appointment with a veterinary behaviorist as the next step. Aggression towards humans is a serious and complex behavior issue that needs to be handled by a professional who can work with your dog in person. The behaviorist will evaluate your dog and help you determine what is triggering the aggression, then put together a detailed training plan to work on the problem. You can search for a board-certified veterinary behaviorist in your area here: www.dacvb.org

I would make sure the dog that has become aggressive isn't having any other issues like pain or discomfort. Also, has anything change in your schedule or house that could have made her feel more insecure or anxious? You could talk to your vet about starting her on an anti-anxiety medicine like fluoxetine as this may help. I would also make sure they aren't becoming aggressive over any treats, bones, toys, etc. I hope this helps and she starts to act like herself soon.