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Jane Lefler
Jane Lefler, Animal Behaviorist
Category: Dog Training
Satisfied Customers: 20218
Experience:  Dog breeder/Trainer and Behaviorist 18+ years
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My English Bull Terrier behaviour is aggressive evening

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My English Bull Terrier behaviour is aggressive in the evening. It's as if she has heard something that is not there, my boxer older dog is afraid of her and gets out of his basket when she is like it. She seems to be startled but nothing there. Some evenings she growls when my dog passes her.  I am very careful when approaching her and she takes a while to calm down. Does she has a tumour or something? She's had a bad ear infection but this seemed to clear after intensive treatment.  She has been quieter than usual but picked up after her ear was sorted.

1.  I'm worried she is going to bite my boxer.

2.  i'm worried she has a brain tumour or something serious.


Hi JaCustomer,
My name is Jane. I have been working professionally with animals especially dogs in both health and behavioral issues for over 18 years. I have over 14,000 satisfied customers. It will be my pleasure to work with you today.
In order to supply you with the best information, I do need to ask for some additional information. Once I receive your answer, it will likely take me about 30-45 minutes to type up your response. I hope you can be patient.
How old is your bull terrier?
Is she spayed or not?
Can you tell me exactly what she is doing?
Can you describe the circumstances surrounding a couple of the incidents?
Is her actions aimed at the other dog, humans, etc?
Does she seem to be shedding more than normal recently?

Customer: replied 4 years ago.

My English Bull is nearly 9. She is spayed.


She is just laying in her basket curled up and I can hear her growl. I go to her to see what is wrong and she just stares at me and looks as if she is about to attack. She isn't baring her teeth or anything. I talk calmly to her and when I feel OK I then stroke her. My other dog gets distressed and gets out of his basket, but when I have calmed the bull terrier down he goes over to her to see if she is OK. that was this evening.


Another occasion and frequently the last few months I hear her growl and look over to her (I have told her off in the past) as it seemed to be directed at my older boxer (he's 11). they have been together for the last 3 years since my son had his children and his partner didn't want the dog around. So she's my girl now. She used to attack doors, and she was stolen about 5 years ago but we got her back and we got used to her passing a doorway without fear of being shut in. We haven't had any problems with her for years.


Customer: replied 4 years ago.

she is not shedding any more than usual.


She also had an ear infection for about a month, she was quiet and didn't enjoy her walk. But this has been sorted now and she perked up the last 2 weeks.


Jane,.I have received your replies and am working on your response now.



thanks for the additional information it is helpful The first thing I would have done is a senior checkup. There are medical conditions that can cause sudden aggression. One is a thyroid condition. The values do not even have to be that far off to cause a behavioral change. Conditions that cause a dog pain can also lead to aggression which is why a senior checkup is the starting point. I'd consider having the thyroid panel run to ensure that isn't the cause. Read about these here:



It is also not unusual for a dog to have seizure activity upon waking. Most people think of a seizure as collapsing and shaking, but a seizure can involve a variety of behaviors including repetitive behavior, growls, and involuntary sounds. Tumors of course can cause seizures but low blood sugar can also lead to seizures so making sure she is fed at least twice a day may help if low blood sugar is to blame. Liver dysfunction can also lead to seizure activity as well which is why a senior check up is a great idea. I do want to give you a site on seizures and you want to read up on the sections related to focal seizures.


Since she is elderly, arthritis may be leading to pain leading to the aggression as well. If this is the case, she may be warning off the male dog so she isn't seen as a weak member of the pack and thus open to aggression from the male. In the dog world, any weakness by another member of the pack can lead to aggression toward the weaker member. So dogs will intimidate the other members to avoid that.


However if all health causes are rule out with testing, then it is behavioral and it would be best not to show her any positive attention when she displays this behavior. Right now you wait a few minutes and then talk to her and stroke her. This can be seen as positive reinforcement for unwanted behavior. Dogs will repeat behavior that gets them attention so you need to make that distinction. If it is behavioral, you will want to keep a leash on her and give her a short tug and firm NO when she displays the unwanted behavior. When she wakes up and does not growl, then reward her with a small treat. This will teach her that you will not allow the aggression toward the other dog or you.


It sounds more like a medical issue to me, but I did want to mention the behavioral part of it. So start with giving more frequent meals and a check up first to ensure she is still healthy and pain free.

I hope this information is helpful to you and you are satisfied with my response. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have .


Jane Lefler and other Dog Training Specialists are ready to help you
Customer: replied 4 years ago.

I've just remembered. Because my dog has had skin problems she had blood tests completed about September last year.


She is fed 3 times a day (because my boxer has pancreatitis and he gets fed x3 per day).


She does have arthritis and she has pain medication for this and supplements.


The aggressive behaviour isn't during the day so I'm inclined and my gut feel is that something is wrong medically.


Thank you I will get her checked out again.

I would appreciate it if you let me know what the results are. She may need some stronger pain medication or have some organ failure related to the medication. .
Customer: replied 4 years ago.

OK thank you. I have been looking at seizures on you tube and she doesn't seem to be same as that but I will get her checked and let you know.