scary strange behavior

Question
Hi! I have a question about my aunt and uncles dog, Ellie. She is a mixed breed about medium size short hair and around 6 years old. They've had her for many years. We've brought our 7 year old female Brittany spaniel, Dixie out there to play with her for the past few years and they have always gotten along, just a few playful fights. Just a few weeks ago Ellie attacked our dog Dixie but we stopped Ellie. It happened again not long after that and she was biting onto my dogs neck and it was kinda bad but we stopped her. Now they told me that Ellie just killed a wood chuck. We are now scared to bring Dixie out there because Ellie has started this behavior. Like I said, they've had her for many years and she's never acted like this. They're now thinking about maybe giving her away. Is there a cause for this behavior? I don't think it's normal, but if it's how she's going to be for the rest of her life then they may give her away. I'm thinking there could be a reason she has started this scary behavior but I'm not sure. Any advice would be great!

Answer
Hi Kylie,

Thank you for writing to me about Ellie.  When a dog suddenly becomes aggressive there has to be either a medical reason or emotional reason.  We start with the medical.  She should be give a full exam and blood panel by her vet including a detailed thyroid test (the thyroid should read center of normal), and a lyme test. Hypothyroidism, or an underactive thyroid gland, could be the reason for a sudden lack of energy in a dog. An ear infection could be the reason a normally sweet dog wants to bite your hand off every time you come near its head.

The vet might want to run a brain scan to make sure there are no tumors.  If no medical reasons for her aggression are found, the vet might want to try some medication.  Also check for worms and parasites. An investigation may reveal that your buddy is scared or in pain!  Pain can be behind a sudden behavior change in your buddy. Gently check her muscles and joints to see she reacts. If she whines or growls when you touch a certain area, let the vet know.  Dogs are quite sensitive. When they are happy, unhappy, stressed or not feeling well, they will communicate this to their owners through their behavior.   

As far as emotional issues, has anything changed within the household recently?  For instance, a dog might hide under the bed because it is afraid of a new member in the house, such as a baby, or even a new piece of furniture.  Is there tension within the house?  Any new residents?  Think carefully.  Could anyone be abusing Ellie?  All avenues have to be considered.   Fear is often a top reason for a dog's sudden behavior change. If Ellie growls, stop what you're doing and try to determine the cause of her fear. Is the dog is growling at a particular person or area?   Closely related to fear, anxiety will change a dog's behavior. It may be the introduction of a new pet into the home, or it may be something as simple as a troubling odor. Consider any changes that have been made in the house to determine what is triggering the anxiety.    The annoyance can be a child who will not stop petting too hard or pulling her tail, and she's fed up.

As dogs age, dementia can sometimes cause sudden behavior changes of various kinds. Your elderly dog may begin to forget who you are and may growl and snap when you approach. A dog may become disoriented and lost in familiar surroundings and may not respond to affection. I do not think that Ellie is that old however.

I hope that these suggestions might lead you to a reason for the change in behavior.  Giving a dog away because they have problems is like getting rid of a child because it has cancer.  This is not Ellie's fault and it's up to the owners to find out what the cause is and then find a way to correct it.

Regards
Shelley Davis