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By 
(Beth Clifton collage)
CORVALLIS, Oregon––Pit bull breeders and dogfighters have argued for centuries over the relative contributions of genetics and “guts” to the making of “grand champions.”
Dogfighters have fed pit bulls gunpowder to try to make them more explosively reactive, aggressive, and “game” for centuries, despite the reality that the working element in gunpowder is saltpeter, the same substance reputedly slipped into military rations to suppress sexual appetite.
Other components of gunpowder include sulfur, likely to give any dog (or human) more aromatic farts, and charcoal, which might help a dog to expel saltpeter from his or her gastrointestinal tract before suffering terminal poisoning.
(Beth Clifton collage)
But “guts,” or more precisely gut microbiomes, may have more to do with establishing and defining pit bull behavior than even dogfighters have imagined in their confusions of analogy with metabolic response.
Research findings published in the January 9, 2019 edition of the peer-reviewed online scientific journal PeerJ “stop short of saying the composition of a dog’s gut microbiome causes aggressiveness, or vice-versa,” summarized an Oregon State University at Corvallis media release about the work of researchers Thomas Sharpton, Nicole Kirchoff, and Monique Udell.
But Sharpton, Kirchoff, and Udell showed, the media release continued, “that there are statistical associations between how an animal acts and the microbes it hosts.”
(Beth Clifton collage)
This, said the Oregon State University publicists, “represents an important step toward more effectively dealing with a canine behavioral disorder that daily puts both animals and people at risk of injury or even death.”
Said Kirchoff, “This lays the foundation for how aggression and gut microorganisms may be connected. To our knowledge no other study has looked at the relationship between dog aggressiveness and gut microbes.”
Aggression, added Udell, “tends to be 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.”
(Beth Clifton collage)
The study, explained the Oregon State University media release, “involved 31 pit bull-type dogs, 14 males and 17 females, who were living at a temporary shelter after having been rescued from a dogfighting operation.
“Upon reaching the shelter, and prior to the start of the research, each dog was put through a series of tests by an animal welfare agency and categorized as aggressive or non-aggressive.
“Animal welfare workers also collected a fecal specimen from each animal so the scientists could analyze the dogs’ gut bacteria.
“Firmicutes, Fusobacteria, Bacteroidetes and Proteobacteria were the dominant phyla among all stool samples,” Sharpton, Kirchoff, and Udell found, “but their abundance differed significantly between aggressive and non-aggressive animals. Proteobacteria and Fusobacteria were more abundant in relative terms in non-aggressive dogs, whereas Firmicutes was relatively more abundant in dogs showing aggression.”
(Beth Clifton collage)
An even more potentially indicative discovery came when Sharpton, Kirchoff, and Udell looked at the gut bacteria clades, a clade being a group of organisms sharing a common ancestor.
“Nine clades within the Bacteroides genus were elevated in the gut microbiomes of the non-aggressive dogs,” Sharpton, Kirchoff, and Udell learned, whereas “25 clades from Lactobacillus were relatively abundant in aggressive animals.”
This finding suggests a potential intersection between the genetic and metabolic aspects of dog behavior.
For example, the Lactobacillus clades of gut bacteria might be more abundant in the most aggressive pit bulls because they help to fuel reactive and violent behavior; or Lactobacillus bacteria might thrive in a canine gut environment that is more often responding to the bodily needs of a reactive, violent dog; or Lactobacillus bacteria might even influence gene expression in the host dog, through “horizontal transfers” of the sort explored by science writer David Quammen in The Tangled Tree: A Radical New History of Life .
(Beth Clifton collage)
None of the relevant questions about the evolution of pit bull behavior can be answered as yet. The Sharpton, Kirchoff, and Udell research, for the moment, just points toward a multitude of further questions.
Depending on what further studies discover, the Sharpton, Kirchoff, and Udell study may suggest ways to make pit bulls safer, or––of keen interest especially to dogfighters––to make them more dangerous.
Alternatively, the whole line of investigation may lead to a dead end.
Meanwhile, said Sharpton, “We’re finding associations between types of organisms in the gut and aspects of vertebrate physiology we wouldn’t have hypothesized about prior to the emergence of microbiome research over the last couple of years. The gut/brain axis, the reciprocal communication between the enteric nervous system and mood or behavior, is a rapidly growing and exciting body of research.
(Beth Clifton collage)
“We didn’t show a cause-and-effect relationship between microbiome and aggression,” Sharpton emphasized, “but we showed they’re correlated, that there’s a linkage. Maybe there’s a microbiome component that contributes to aggressiveness, but we need follow-up experimentation to determine if there is a causative role.”
The Sharpton, Kirchoff, and Udell paper is formally titled “The gut microbiome correlates with conspecific aggression in a small population of rescued dogs (Canis familiaris).”
Says the abstract, “Aggression,” which Sharpton, Kirchoff, and Udell left undefined, “is a serious behavioral disorder in domestic dogs that endangers both dogs and humans. The underlying causes of canine aggression are poorly resolved and require illumination to ensure effective therapy.
(Beth Clifton collage)
“We hypothesized that the composition of the canine gut microbiome could associate with aggression,” testing the hypothesis by analyzing fecal microbiome samples collected from “21 dogs who displayed conspecific aggressive behaviors and 10 who did not. Beta-diversity analyses support an association between gut microbiome structure and dog aggression.
“Additionally, we used a phylogenetic approach to resolve specific clades of gut bacteria that stratify aggressive and non-aggressive dogs,” the abstract continues.
“Although sample size limits this study, our findings indicate that gut microorganisms are linked to dog aggression and point to an aggression-associated physiological state that interacts with the gut microbiome. These results also indicate that the gut microbiome may be useful for diagnosing aggressive behaviors prior to their manifestation and potentially discerning cryptic etiologies of aggression.”
(Beth Clifton photo)
Asked ANIMALS 24-7, “Are we correct in presuming that the major source of gut microbiome in a dog would be from the mother, either passed through the placenta or through nursing, and that relatively little of the gut microbiome would be acquired later, through food?
“Do you have any idea to what extent the characteristics of a dog’s gut microbiome might be changed post-weaning, whether through feeding, medication, or any other process?
“We are particularly eager,” ANIMALS 24-7 mentioned, “to see the results from comparison of the gut microbiomes of the pit bulls in your study to those of other types of dog.”
(Beth Clifton collage)
Responded Sharpton, “Exploration of our observations in other breed types is needed. I do not think,” Sharpton added, “that we can assert that most of the microbiome is inherited from the mother, or that relatively little of the microbiome would be acquired later on.
“In fact,” Sharpton said, “while there is still extensive open discussion about the heritability and source of the gut microbiome in mammals, it is clear that while some taxa are acquired from the mother, many of the taxa (dare I say most) are acquired later in life through the process of microbiome succession.
“The gut microbiome starts out as being relatively simple early in life,” Sharpton explained, “i.e., few types of gut taxa, and massively diversifies into a complex assemblage of organisms as the individual matures, until early adulthood, wherein the microbiome tends to be relatively stable.
(Beth Clifton collage)
“This maturation process of the microbiome would suggest that environmental factors play an important role in determining which kinds of taxa occupy the gut,” Sharpton said, “though host genetics––which confounds direct maternal inheritance––could select for specific assemblages from the environment in a manner that elicits ‘breed effects’ on the microbiome.
“Note,” Sharpton added, “that since not all pit bulls display aggression,” a claim which depends on how “aggression” is defined, “that if the microbiome plays a role, then this environmental influence on the composition of the microbiome could be an important driver that defines differences in aggressiveness across individuals.”
This response, like the rest of the Sharpton, Kirchoff, and Udell paper, mostly raised further questions.
(Beth Clifton collage)
Suggested ANIMALS 24-7, “Among the many questions your research raises is the extent to which ‘aggression,’ as measured in behavioral assessments oriented toward preventing ordinary bites, actually predicts dangerous behavior, in which biting rapidly escalates into mauling––including especially grip-and-shake, in which the bite is only preliminary to the most damaging part of the attack.
“The phrases we most often hear after pit bull attacks,” ANIMALS 24-7 pointed out, “include many variations on ‘He/she was a sweetheart, never showed any signs of aggression, might have licked you to death,’ etc.
“It is possible, though, that gut microbiome findings might help to explain how and why many of these “sweetheart” dogs suddenly and unpredictably detonate.”
(Beth Clifton collage)
Sidestepped Sharpton, “There are many reasons there could be a link between aggression and the microbiome that do not involve gut taxa influencing behavior. I think that future research will help answer this question of causality and, with any luck, ultimately help us mitigate aggressive behaviors in our four legged friends.”
Neither Sharpton, nor Kirchoff, nor Udell responded to further questions from ANIMALS 24-7 pertaining to definitions of “aggression” and how gut microbiome might specifically influence the evolution of pit bull behavior, both within individual pit bulls as they grow and within pit bulls as a class of dog.
John P. Colby & Bill. One of Colby’s pit bulls in 1909 killed his 2-year-old nephew, Bert Colby Leadbetter.
Historically, pit bulls were bred almost exclusively for fighting until just the past few decades, and were traditionally “line-bred,” as dogfighters and breeders catering to the dogfighting industry sought to develop and establish their own unique brands.
Along the way, fighting dog breeders such as John P. Colby, Earl Tudor, Charles Werner, and J.D. Johnson produced the ancestors of most pit bulls today, and popularized brand names including Staffordshire, American Pit Bull Terrier, American bully, et al.
Apart from strictly physical attributes, such as size and agility, favored in varying degree by different fighting dog breeders relative to each other, pit bulls have been bred for three “fighting” behavioral traits, differing from the behavioral traits of most other dogs.
Earl Tudor & Jack Swift, 1915.
“Aggression,” as measured through behavioral assessments of fully grown dogs, might be summarized as just the tendency of the dog to seek dominance.
However, while many dog breeds are commonly described as “aggressive,” most of them are relatively rarely involved in fatal and disfiguring attacks, because most of their “aggressive” behavior is limited to barking, lunging, and sometimes giving a warning bite before retreating a few steps to see if the other dog (or human) retreats.
The other two traits that have historically been most sought in fighting pit bulls are “reactivity” and “gameness.”
A Colby-line pit bull today.
“Reactivity” in the case of a fighting dog means that the dog skips giving the normal canine warning signals and launches immediately from seeming repose into all-out attack.
This appears to be the first and most obvious distinction between pit bull attacks and those of practically all other dogs. Dogfighters breed for reactivity because in fights to the death, the dog who hesitates to give warning signals to an opponent, instead of fighting, will soon be killed and not pass along any genes––or any gut microbiome, for that matter.
(YouTube image)
“Gameness” refers to the willingness and ability of the pit bull to fight on, despite injuries of any severity. A “dead game” pit bull is one who achieves a “death grip” on another in a fight, and does not let go even if the “dead game” pit bull is killed.
While proven “dead game” pit bulls pass along no genes thereafter, dogfighting breeders have historically made quite a lot of money selling the closest line-bred relatives to their “dead game” dogs.
However, while the gut microbiome in a puppy is relatively simple, and becomes much more complex later, the traits of reactivity and gameness are commonly tested very early in a fighting pit bull puppy’s life.
Pit bulls, for example, will often snap at stimuli soon after birth, unlike other puppies, and will latch onto a bite stick so tightly that they can be lifted into the air with the stick before they have their eyes open.
(From YouTube video)
By the time fighting pit bull litters are weaned, the puppies are already fighting among themselves, and sometimes will kill each other if not promptly separated. This tendency is the main reason why pit bulls have never been produced successfully at large factory-style “puppy mills.”
Historically, fighting dog breeders have believed that genetics accounts for practically all of this behavior, contrary to the prevailing belief among dog rescuers that “It’s all in how you raise them.”
The gut microbiome of fighting pit bulls might diversify early in their lives from sources other than nursing and placental transmission, for example through coprophagia (eating poop), but even this source would come almost entirely from the mother and litter mates, since pit bull litters are normally kept away from any adult pit bulls other than their mothers, lest the older pit bulls kill them.
Beth & Merritt Clifton
In view, therefore, that the defining traits of fighting pit bulls tend to be established much sooner in life than sources of gut microbiome from diversified sources might be expected to have an influence, the Sharpton, Kirchoff, and Udell research seems to suggest mainly that gut bacteria may have an activating or compounding effect on genetic traits which are already present in pit bull puppies at birth.
Filed Under: Breeding, Culture & Animals, Dog attacks, Dogfighting, Dogs, Dogs & Cats, Feature Home Bottom, Uses of dogs
I found this association interesting, but I wonder, for example, what was called aggression. Food bowl? Dog? Human? Cat? Etc. Was the slightest aggression called aggression? Or was the term aggression used for dogs that appeared to be serious biters in every scenario? Was this a blind study? In other words, did those evaluating the lab results already know to which group the dogs belonged? Did any dogs change their level of aggression as time passed? Did some become more confident which could have made some dogs become less aggressive? To what category did very slightly aggressive dogs belong? Were kenneling conditions all the same? Was all dog food identical? Did some dogs show aggression to some people but not to others? Was any dog treated with antibiotics that could alter gut flora?
I think the study is interesting, but I wonder how one can be certain the dogs were classified correctly. Could anyone actually properly call these dogs aggressive or non-aggressive? Why not list them on a scale of 1 to 10? That would provide a lot more categories.
Thank you for your active attention to the fact that this is just the beginning of a long road towards understanding even if the gut microbiome contributes to aggression, much less how it does so. We hope to continue advancing this research and look forward to sharing subsequent discoveries in the years to come.
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