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Behavior Specialists Help Aggressive Dog Get Along with Companion

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UC Davis behaviorists helped Stella get along with her companion Guinness. (Photo courtesy of Soulful Pet Photography.)

VMTH "Case of the Month" - October 2015

When Stella, a 1-year-old Welsh terrier, began showing frequent and severe aggression toward her companion Guinness, another Welsh terrier, her owners brought her to see the behavior specialists at the UC Davis Veterinary Medical Teaching Hospital. Stella was brought into the house when she was a puppy and Guinness was 2. Things went well between the two terriers for the first year, but soon after, especially during times of high arousal (such as when their family returned home, or around a favored toy), Stella would suddenly attack Guinness. Her attacks would include clamping down on Guinness’ neck, refusing to release even when her owners tried to pull her off.

After one particularly aggressive attack, Guinness had to be treated for puncture wounds. Their owners rightfully sought help with the UC Davis Behavior Service. Based on an extensive history, video footage of the dogs in their home environment, and in-person interactions during their consultation, Stella was diagnosed with anxiety with multiple triggers, and offensive dominance-status aggression towards her housemate dog. Guinness was assessed as having normal canine behavior – he was simply a victim of Stella’s aggression.

While there are several possible underlying motivations, in Stella’s case it was determined that the dogs had an unstable hierarchy. Stella showed clear signs that she was the most dominant dog in the home, and Guinness usually backed down from her without complaint. The fights seemed to break out in situations when Stella perceived that Guinness was given preferential treatment by the owners.

Pet owners naturally want to give attention and resources equally due to humans’ sense of fairness and equality. However, when dogs live together in groups and need to share resources, they sometimes form stable hierarchies in which the most dominant dog gets preferential access to resources. Fairness and equality sometimes play no part in their natural world. While aggression is often involved in establishing the hierarchies, they eventually serve to reduce aggression, because each dog knows its place in the pecking order. It is important to recognize that these hierarchies only exist between dogs. The idea that dogs form dominance hierarchies with humans has been disproven. 

To stabilize the hierarchy, Stella’s owners were asked to treat Stella preferentially when distributing resources. When they came home from work, they were to give Stella more attention than Guinness. If they were putting down food bowls, or handing out treats, Stella was to get served first. Stella was also started on a daily anti-anxiety medication to help with her excessively anxious reactions to various additional daily triggers.

Both dogs were also started on a reward-based leadership program. The program helped to improve Stella’s response to her owner’s cues and to build up her confidence. No physical or verbal forms of punishment are used in this program. 
At their follow-up appointment one month later, Stella and Guinness made significant improvement. Both dogs enjoyed the frequent training, and Guinness did not seem to mind receiving resources second. Stella responded well to her medication and showed less frequent anxious responses to noises and outdoor triggers. Most importantly, her aggression toward Guinness was both less frequent and less severe.

At that stage in their treatment plan, desensitization and counter-conditioning training was introduced, with the goal being to teach Stella appropriate calm behavior in response to Guinness’ presence. Their owners set up structured interactions between the two dogs, and rewarded Stella for showing desirable behavior, while preventing them from becoming too aroused by adjusting the distance, intensity, and duration of the exposure.

In the six months since, Stella has continued to show steady improvement. She and Guinness now have a positive and mostly peaceful relationship. Because of this success, their owners have even been able to foster new dogs in their home.  

About the Veterinary Medical Teaching Hospital
The William R. Pritchard Veterinary Medical Teaching Hospital at the University of California, Davis—a unit of the #1 world ranked School of Veterinary Medicine—provides state-of-the-art clinical care while serving as the primary clinical teaching experience for DVM students and post graduate veterinarian residents. The VMTH treats more than 51,000 animals a year, ranging from cats and dogs to horses, cows and exotic species. To learn more about the VMTH, please go to Timely news updates can be received on its Facebook ( and Twitter ( pages.

Media Contact:
Rob Warren
VMTH Communications & Marketing Officer