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Why is my 9-month-old dog becoming aggressive with strangers?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Large (61lb +) | Female | spayed | 9 months and 21 days old | 65 lbs

Hi I have a lab/ pyrenees mix Maggie who is 9 months old she is getting more aggressive towards people and dogs she doesn’t know the more she gets older. I bought her a muzzle and a shock collar to help but hasnt done anything. Do you have any advise or know if something might be wrong with her. All attach a picture of her so you know what she looks like.

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1 Answer

Most Helpful Answer

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Answered By Shaneez Wallani, DVM

Veterinarian

Published on January 24th, 2019

Maggie may be acting protective, she could be anxious or fearful, leading to her acting aggressive, or she may be displaying territorial behaviour. It is very important that you seek the advice of a veterinary behaviorist to help curb this behavior. If left untreated, Maggie may learn to think it is ok to act this way towards humans and animals in general, and could then potentially bite and injure someone. Please work with a veterinary behaviourist immediately. Hopefully she will improve with training and learn what is and is not acceptable behaviour. I would advise keeping her on a leash and away from other animals and people until you have the chance to work with a behaviourist. If you do not see signs of improvement, see a veterinarian to rule out medical causes, and to see if medical therapy is indicated for her behaviour. It is also essential to make sure she is up to date on her vaccinations, particularly her rabies vaccine. Visit https://www.dacvb.org/ and www.aspca.org/pet-care/general-pet-care/behavioral-help-your-pet for information on how to find behaviour help near you.

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