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New Research: Aggression Linked to Gut Microbes of Some Rescue Dogs

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New Research: Aggression Linked to Gut Microbes of Some Rescue Dogs

It seems odd to assign behaviors of dogs to something that could be found in their gut. It makes most sense that their demeanor, behavior, personality, and so on would be dictated by well, the brain, and not their stomach, right? But new research from Oregon State University suggests something as simple as microbes found inside canine’s guts could influence how aggressive they are. 

Similar to research that had been done on mice with anxiety disorders, the researchers tested 31 “pit bull type dogs” they’d found through a rescue organization. Each of the dogs had been previously tested for aggressiveness, making the “pit bull type” classification used to find their research sample that much more interesting to, begin with, and also relevant to developing our understanding of aggressive behavior in dogs. 

And what exactly did they test? The dogs’ feces for the presence of microbes. What they found is a common thread between aggressive behavior from the dogs and the specific types of microbes present in their gut. They found firmicutes, fusobacteria, bacteroidetes, and proteobacteria were dominant in all stool samples of the 31 dogs. Interestingly, there was a significant difference in the presence of those microbes from aggressive to non-aggressive dogs in the study. Non-aggressive dogs had a greater abundance of proteobacteria and fusobacteria in their stool samples and firmicutes was noticeably more abundant in the dogs that showed more aggressive behavior. Now, the researchers apparently wouldn’t flat out declare a correlation between the two (aggressive behavior and the microbes in the dogs’ guts) but there was a statistically strong enough association between the two for them to take notice and recognize the link. That alone was enough to potentially lead to more research on the subject, as Thomas Sharpton, an assistant professor who specializes in microbiology and statistics, said their findings will need to be validated with other populations of dogs and even with additional breeds. 

“Maybe there’s a microbiome component that contributes to aggressiveness, but we need follow-up experimentation to determine if there is a causative role,” Sharpton said. “We’ve opened a new door. It will require appropriate resources to find out what is on the other side.”

“In terms of how microbes potentially influence dog behavior, this lays the foundation for how aggression and gut microorganisms may be connected,” said lead author and microbiology student at the university, Nicole Kirchoff. “To our knowledge no other study has looked at the relationship between dog aggressiveness and gut microbes.”

“Aggression is really stigmatized,” said Monique Udell, an assistant professor and animal behavior researcher who participated in the research. “It tends to get viewed as a shortcoming of the individual animal. But it’s important to look at aggression and other behavioral syndromes in terms of physiology as well. Maybe there are underlying physiological causes we can address, or if not, maybe there are behavioral predictors with physiological implications.”

The potential for more research on the topic definitely adds to the “nature versus nurture” debate surrounding certain dog breeds and aggressive behavior. Within the past month, another study published findings that supported the simple idea that a dog’s personality is in fact rooted in the DNA of its specific breed, observing data from more than 17,000 canines of over 100 different breeds. Their questionnaires for dog owners and data examined 14 different personality traits among dogs and they determined that “breed differences in behavior are highly heritable, and that clustering of breeds based on behavior accurately recapitulates genetic relationships.” In particular, three behavioral traits were found to be most likely to be inherited: trainability, chasing, and a tendency to be aggressive toward strangers. 

"Our findings suggest that dog breeds also provide a powerful and highly tractable model for questions about the evolution and genetic basis of behavioral traits,” the researchers reported. 

"It's a huge advance," Elaine Ostrander, a mammalian geneticist at the National Human Genome Research Institute in Bethesda, Maryland, who was not involved in the study, told Science Magazine. "It's a finite number of genes, and a lot of them do make sense.”

"Aggression is incredibly complex. It's going to be both situation-dependent and dependent on the history of both the people and the dog," Stephen Zawistowski, science adviser to the American Society for the Prevention of Cruelty to Animals (ASPCA), told HealthDay. "You can't just pick the breed of the dog and say somehow that will be predictive of whether the dog will be aggressive.” 

But no matter the research or the breed, there are of course always things you can do to minimize and manage aggression as an owner. “Bad dog behavior and dog problems are not premeditated. Bad things happen when powerful breeds (or mixes of powerful breeds) live with humans who like the breed but don’t understand and fulfill the animal in the dog,” writes Cesar Milan. “Many people consider the look or popularity of a breed before thinking about whether the dog works for their lifestyle. This is a recipe for disaster.” 

One of the simplest things a dog owner can do for a potentially aggressive dog is ensure they are getting their pup enough exercise. Milan points out that many aggressive dogs simply suffer from a lack of adequate exercise. Acting on that aggressive energy is a result of them having no other healthy outlet for it. And what he refers to as “red zone dogs” — breeds that are potentially frustrated animals as well as powerful breeds — are always best cared for by owners ready to lead them. “You must gain control of the situation and dog behavior before it escalates,” he explains. “When dealing with red zone dogs, I start by working with the owners, explaining how to establish themselves as the pack leader and to understand the animal in their dog. This is a crucial part of rehabilitating your dog and overcoming dog problems: changing your behavior. If you revert to your old ways, so will your dog.” 

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