Why is my dog suddenly aggressive at dog park?

His behavior could have a variety of motivators from being fearful to being territorial or even just being frustrated that he can’t meet the other dog. If he is allowed to pull on the leash, stops to sniff every 5 feet, and pees on all of the trees, then he will think that he is walking you. This means he won’t listen to you when he sees another dog. If you react when he does then you will only add stress into the situation. Try to stay as relaxed as possible when you see a dog or when he lunges. Practice having him walk next to you on a loose leash. Have him sit multiple times on a walk just because you asked him too. You can also change your walking speed or normal route. All of these things will help him learn that you are in control on a walk. If you are in control, then he needs to listen when he sees another dog.

If the dog has an illness that has caused him to suddenly become aggressive the veterinarian will prescribe the appropriate medication if needed e.g. pain relief and anti-inflammatories for joint disease. Making sure that your home environment is calm and predictable may be a recommendation by the veterinarian or behavioral therapist. If you do not have a routine with your dog, and his day-to-day living is very unpredictable, a change will need to be made. Consistent and proper routine management is one step to helping dog aggression. Behavioral therapy may include modification of the dog’s behavior, desensitization, eliminating triggers, training and much more. The behavioral therapist must get to know your dog and may come into the home to help you, and will even teach you strategies to help your dog. This may take time, and things may have to be eliminated from the dog’s life in order to decrease his aggression, but will be worth it in the end.