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Jack Russells/Sudden aggression in puppy


Hi Carol, I have an 8 month old Parson Russell Terrier who has been the sweetest thing since we got her at 9 weeks. We have had her in obedience, leash skills and puppy playgroup since about 12 weeks, and she has always been a doll, the behaviorist that monitors the playgroup even talked about the possibility of her being a therapy dog (which I wasn't necessarily interested in, but it illustrates how totally sweet she is, especially for this breed). Well, we went to playgroup yesterday, just like normal, and she was super-aggressive with two other dogs, both dogs she had played with before, and we had to take her home. I thought it was the strangest thing, and the behaviorist was completely surprised too.

However several things happened recently, first that she was ill over the weekend (she was cleared by the vet and the behaviorist to return to playgroup), second that the week before last we began using a correction collar in leash skills class, though she didn't seem to mind it and responded really well in class, and third that she caught our neighbor's chicken in our back yard on Sunday (I got to her just as she caught it, so she didn't do any damage, thankfully, but it was a totally new experience for her).

I am praying that she just still wasn't feeling well after her illness this weekend, but I am terrified that this is the new normal for her. If it was that she was still feeling bad, is there a chance she will just go back to her old self when she is better? Or could the correction collar or the chicken incident have changed something about her? Is she being a teenager and developing a surly personality? I am not sure what to do. The behaviorist said we could try again cautiously next week, but I am totally freaked out.

Thanks so much,


Pups are still growing and forming their personalities for up to a year and you have a great deal of time and effort put into this little girl.  I think she probably just had an abundance of energy on this particular day from being cooped up in the house sick.  Try to take her to the park again, but before you go, make sure you walk her or run her to burn off some of that excitement/energy ahead of time. This is a recommended suggestion to anyone who will be visiting a dog park.  I doubt very much the chicken had anything to do with it - and stick to Martingale collars. ANY correction, chain or spiked collars are bad news.
If she acts up again, immediately remove her from the park and repeat this over and over, she will eventually learn that behavior reaps no rewards.  
Aggressive behavior just can't be tolerated - especially at the dog park.  
Best of luck, and good job with her!!!

Sorry I didn't answer sooner, my dog had medical issues this week, been tough and I
haven't checked my email in 2 days.  

Take care

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Carol F


Questions on "Jack" Russell Terriers pertaining to their health, well being, general questions on breed, types, size, shape, health, personalities, behavior problems, genetics, so called standard, what to look for when purchasing, and if you would be a good match with this wonderful and unique dog. Too many times, people buy jack puppies because they are absolutely adorable, and then a few months down the road they own this dog that they know nothing about and haven't prepared or trained for. I love the breed and everything about them and hope to provide some help, education and advice to current and prospective owners. I am a veterinary technician, dog trainer and breeder of Jack Russells.


I own four Jack Russells and I have been working with dogs for 30 years. My personal interest is in helping educate people about the very special qualities of this breed. I advocate education and research of the breed before you buy one, they are wonderful pets if suited with the right person/family. Do your homework first! I can help you determine if you are a good match with this breed. I want people to know also that there are two types of Jack Russells, the Parson hunter with long legs and the Shortie or Russell Terrier and their very distinct differences. I also hope to allay fears about their CRAZY reputations - which is not always the case. ~*~*~*IMPORTANT, PLEASE READ*~*~*~ PLEASE NOTE: I DO NOT ENDORSE THE SALE OF ANY JACK RUSSELLS OR JACK RUSSELL PUPPIES THAT MAY BE ADVERTISED ON THIS PAGE. BEWARE OF PUPPY MILLS OR OTHER PLACES THAT SELL MANY DIFFERENT DOGS OVER THE INTERNET. ALSO I DO NOT ENDORSE ANY VIDEOS OR TRAINING TAPES THAT ARE ADVERTISED ON THIS PAGE. I WILL BE HAPPY TO HELP YOU PICK OUT A REPUTABLE TRAINER/VIDEO SERIES OR EVEN PUPPIES IF PRIVATELY ASKED. I DO NOT ENDORSE ANY SALES ADVERTISEMENTS ON THIS PAGE.

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Veterinary Technician - Newbury College 1982 - 1985

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