Canine Corner

The human-animal bond

Aggression between Dogs in the Same Household

What causes conflict between dogs living in the same home?

 dog canine pet human animal bond aggression conflict fighting stress
My home typically contains two or more dogs, and research has shown that having more than one dog is typical for nearly one third of dog owning households in North America. In a multiple dog home probably one of the most disturbing situations is when there are aggressive incidents between the dogs. These are not only disturbing for the peace and happiness of the humans living there, but it can also be quite dangerous for the dogs and for the people who try to intervene and break up the fight. A scientific report published in the Journal of the American Veterinary Medical Association* looked at this issue, specifically assessing the characteristics of the dogs involved and what can be done to help eliminate the problem of fighting among dogs living together.

Researchers Kathryn Wrubel, Alice Moon-Fanelli, Louise Maranda, and Nicholas Dodman, recruited 38 pairs of dogs that came to the Animal Behavior Clinic at Tufts University Cummings School of Veterinary Medicine in Grafton, Massachusetts specifically because they were involved in aggressive incidents with their housemates. The research team then conducted in-depth interviews and administered a number of questionnaires in order to determine the characteristics of dogs which had been involved in such situations. Later on they would prescribe a treatment method for the problem.

The first thing that might be surprising to most people is that female dogs are more often involved in such fights then are males. Only 32% of the aggressive incidents involved conflict between two males, while in the remaining 68% females were active participants. This is consistent with some previous research which has shown that when females get into an aggressive situation injuries are apt to be more severe and the fight tends to be longer and more furious.

If we look at the overall characteristics of the dogs involved, we find that the instigators of the aggression are usually the dog who has been most recently brought into the household (70%). Furthermore in 74% of the cases it is the younger dog that starts the fight. These fights are often a surprise to the owners, since 39% of them claim that the dogs usually get along with one another most of the time. The conflicts can be quite intense which is proven by the fact that 50% of them required veterinary care for the dogs and 10% of them required medical attention for the owners who tried to intervene. The reason that the owners were placing themselves in jeopardy was because 54% of them felt that the fight would not stop unless they separated the dogs physically, and only 8% of them successfully separated the dogs using learned obedience commands.

What tends to trigger a fight among housemates? The actions of the owner, such as paying attention to one dog rather than the other, are a trigger for 46% of the pairs. Simple excitement, usually involving the owner's arrival or other activities was involved in 31%. Conflict over food was involved in 46% of the pairs while found items or toys are triggers in 26%.

There appear to be a number of risk factors which the study isolated for one or both of the dogs. Among the pairs of dogs involved in aggressive incidents 41% had at least one member who had lived in multiple households. When at least one of the dogs in the pair was 12 weeks of age or older when adopted the rate of conflict was 39%, dogs adopted from a shelter were involved in 33% of the cases and dogs from pet shops in 16%.

There is some evidence that dogs involved in aggressive situations with the dogs that they live with do have a tendency to show aggression in other situations. For example, 40% have shown aggression to other dogs, 27% have shown aggression toward humans living in the household, and 27% toward human strangers, but most distressingly 20% have shown aggression toward their owner.

Aggression may not be their only problem since 50% of the pairs of dogs involved in conflicts had at least one member with noticeable separation anxiety, and 30% had phobias, fearfulness, and other forms of anxiety.

The good news is that aggression between housemates does appear to be treatable using behavioral techniques that owners can institute at home. The first of these is the technique that Nicholas Dodman calls "nothing-in-life-is-free". This simply requires the dogs to respond to some simple learned command (such as "sit", "down", "come" etc.) before they get any resource that they want (their meal, a treat, petting, attention and so forth). The second of these involves "supporting" one of the dogs, meaning that the chosen dog gets everything first (food, treats, attention etc.). Here the problem is which dog to select, and a pragmatic way of doing this is to choose the dog that is larger, stronger, healthier, more active and so forth. An alternate way (which seems to fit with human notions of priority, deference and respect, is to select the "senior" dog, where here the word "senior" means the dog which was in the household first, and has lived for the owner the longest. Both of these methods work, but not instantaneously since on average the data shows that noticeable improvement does not occur until more than five weeks after the process starts. The "nothing-in-life-is-free" technique produced improvement in 89% of the pairs, while the "senior support technique" produced improvement in 67% of the pairs. The researchers suggest that these techniques work for two reasons. First, because the dogs must act in a controlled manner, this takes some of the excitement and arousal out the situation. Secondly, because events occur in a predictable order, and the dogs learn that each of them will eventually get what they want and no conflict is needed.

It is important to note that the sex of the dogs not only makes a difference in the likelihood of conflict but also in the likelihood of improvement with behavioral treatment. As we noted in the beginning of this article, female dogs are more likely to engage in conflicts with their housemates and their fights are apt to be more serious. This is consistent with the fact that the improvement with behavioral treatment is found to be less pronounced, although still significant, in female pairs. In the male-male pairs, conflict was reduced in 72%, of the cases while for male-female pairs the reduction was 75%. In the female-female pairs the reduction was for only 57%, which, although not as large as in the other pairings is still a reasonable improvement rate, and well worth the effort.

To read more about canine aggression click here.

Stanley Coren is the author of many books including: The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; The Left-hander Syndrome

 Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission

*Data from: Kathryn M. Wrubel, Alice A. Moon-Fanelli, Louise S. Maranda, and Nicholas H. Dodman (2011). Interdog household aggression:38 cases (2006–2007). Journal of the American Veterinary Medical Association, 238, 731–740

Stanley Coren, Ph.D., F.R.S.C., is a professor of psychology at the University of British Columbia.

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