We may think our dog wIll take a treat from any hand that offers it, but a new study by a team of Japanese researchers suggests that may not be the case. Primates engage in something called “social eavesdropping”— essentially, making judgments about others based on interactions that don’t directly affect their own interests. This study tested dogs’ ability to do the same by setting up situations in which the dogs’ owners asked for help in opening a box and were assisted (helper scenario), rejected (non-helper scenario), or ignored (control scenario) as the dogs looked on. After these interchanges, when the dogs were offered treats, they took them randomly from Helper and Control “strangers” but were biased against non-helpers. According to Kazuo Fujita, professor of comparative cognition at Kyoto university and one of the study’s authors, the ability to socially and emotionally evaluate others “is one of the key factors in building a highly collaborative society.” So, another step in the process of understanding how Canis lupus became familiaris: like humans, dogs are able to pick up clues about who to trust and who to avoid.
Culture: Science & History
How Humans and Their Dogs Drove Neanderthals to Extinction
Pat Shipman, PhD, is a retired adjunct professor of anthropology at Penn State and an internationally recognized expert in taphonomy, the study of how living animals are transformed into skeletons, and then fossils. Her scientific training and boundless curiosity lead her to take on the intriguing question of just why Homo neaderthalensis, one of the most successful apex species of hunters who had thrived for millennium in Eurasia, would almost suddenly, anthropologically speaking, become extinct. Her hypothesis: The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction (The Belknap Press) points to the abilities of both certain wolves and our ancestors to pair up and this gave them the competitive edge in the battle of survival. It is certainly true that this wasn’t done intentionally, but such an evolutionary breakthrough resulted in an alliance that had devastating effects on not just the Neanderthals but on a long species list including the huge woolly mammoth, saber-toothed tigers and Cave bears. Could it be possible “man’s best friend” have been the Neanderthals’ worst nightmare ? Shipman’s thesis starts with Homo sapiens, who in expanding north out of Africa were not only as an invasive species, but the most invasive in history, wreaking ecologically enormous changes throughout continents. The evidence that she relies on, by a meticulous review of the most current archeological research and genomic and genetic studies, can perhaps most readily be seen in the mammoth remains megasites, where the number of kills increases almost exponentially after the first evidence of the wolf-dog–human alliance was discovered. For ten thousand years before the domestication of the wolf-dog, evidence of early humans hunting mega-fauna like mammoth is scant, but with the addition of the superior hunting and tracking talents that wolf-dogs contributed to our projectile throwing ancestors lead not only to more successful kills of large prey but insured the success of our two predatory species. As for the Neanderthal, it wasn’t just simply that humans bested them as hunters but climate change was also a key contributing factor: but the combo of the alliance of the apex predators with the ice age ensured their extinction, so goes evolution. As Shipman notes about the Jagger Principle, “… the immortal words of Mick Jagger (yes that one) and Keith Richards are the best statement I know of to describe evolution. Things don’t stay the same; you can’t always get what you want; but with a little flexibility, you might get what you need to survive.” This is truly a fascinating and thought-provoking book, and Shipman presents a compelling argument for how canines and humans proved their flexibility and how this could have been the main reason that we survived and the Neanderthals didn’t. But drawing upon the wisdom of another ’60s duo, we also got by with a little help from our [first] friends. See the following interview with Dr. Shipman to learn more.
Bark: How long did it take humans, once they migrated out of Africa, to team up with wolves, a species that was unknown in Africa?
Pat Shipman: There were wolves in North Africa, but my guess is that humans did not team up with them but rather, based on genetic information, with European wolves. The earliest humans in Europe date to perhaps 42,000 years ago. The earliest wolf-dogs we know at present show up about 34,000 years ago (or about 37,000, if the raw radiocarbon date is calibrated for irregularity in the deterioration of C-14). Thus, it may have taken 6,000 years, or less—I seriously doubt we have found the first wolf anyone ever attempted to domesticate.
BK: What environmental reasons led to this amazing partnership?
PS: There were many different predators in Europe when modern humans arrived; competition for prey was considerable, and even worse once humans came on the scene. The idea of domesticating any animal was completely unknown, but somehow— probably by accident—some wolves began cooperating with some humans because the alliance benefited both.
They caught more prey, faster, with less risk to canine or human, which meant more energy for reproduction. Wolves had a set of skills for hunting in packs: speed, keen ears, a very keen sense of smell, sharp teeth and claws. Early humans were much slower, had lousy senses of smell and hearing, and blunt teeth, but they had distance weapons that could kill an animal while avoiding injury from close contact. By teaming up with special wolves—wolfdogs they could capture a much wider array of animals with much less risk and less expenditure of energy. They were nearly unstoppable.
BK: You write that proto-dogs were like “living tools” to humans. Was this a mutually beneficial arrangement?
PS: Absolutely. You cannot force any animal to cooperate if it does not want to. You cannot force an animal not to be hostile to humans or to cooperate with humans if there is no benefit to the animal.
BK: Wolves are highly territorial, and may kill other wolves who come into their area. Since this was well before human settlements, humans and wolf-dogs would have traveled great distances, through other species’ (i.e., wolves’) territory. Could the advantage to the wolfdogs come from the protection offered by their human partners?
PS: Both wolf-dogs and humans were more efficient hunters through cooperation— the wolf-dogs by having hunters kill the prey from a distance after they had found it, isolated it and stressed it through charging and holding it at bay.
For wolf-dogs and humans to travel together, they must have cooperated to drive off or kill the wolf packs through whose territories they passed. Indeed, there is a marked rise in the number of wolf bones in human sites after wolf-dogs appear. I think wolves were deliberately targeted by humans in order to protect the wolf-dogs, and to protect the remains of their kills from scavengers.
BK: Why do you think that Neanderthals did not also have wolf-dogs?
PS: One quite real possibility is that modern humans had adaptations that fostered better communication with wolf-dogs and possibly (we don’t know) Neanderthals did not. For example, humans are the only primates with whites to their eyes, which makes communicating the “direction of gaze”— where you are looking—very obvious. This is a huge advantage in silent cooperative hunting. We do not yet know if Neanderthals had this adaptation or not. Assuming that they saw humans working with wolf-dogs, why Neanderthals did not steal them or make their own is unclear. Humans undoubtedly prized the canines and may have gone to great lengths to prevent them from being stolen. Maybe Neanderthals did not have the empathy and ability to understand wolf-dogs that is so necessary to a good working relationship. Maybe Neanderthals tried and just couldn’t figure out how to handle them.
BK: What do you think inspired humans to see that teaming up with wolves might give them a competitive edge? Did it have to do with their diet perhaps?
PS: I don’t think humans set out to domesticate wolves into dogs; I think it was an accident based on taking in orphaned puppies and raising them. Before working with wolf-dogs, humans were rarely able to kill mammoths or other very large game; afterward, there are sites with dozens of mammoth kills. I suspect that killing mammoths efficiently and regularly required the help of wolf-dogs, so mammoths weren’t really a preferred human food until humans had wolfdogs to help.
BK: It was interesting that the primary protein source in the bones of both wolfdogs and humans can be detected. What does that tell us?
PS: First, this sort of study tells us that, at the same site, wolf-dogs and wolves ate different prey animals predominantly. (That is a very surprising finding if my colleagues and I are mistaken and the wolf-dogs are really wolves, that would make them a very odd and distinctive group.) Second, this type of study shows us that humans may have provisioned wolf-dogs, rather than letting them simply eat whatever was left over.
BK: You say that wolf-dogs were a first, but unsuccessful, attempt at domestication; and that domestication happened several times in different areas. Are you concerned that their mtDNA (mitochondrial DNA) evidence hasn’t been found in modern-day canids?
PS: Not at all. There is as much mtDNA evidence that these identified wolf-dogs were wolves as there is that they were dogs: none. The mtDNA we have so far from wolf-dogs is unique, previously unknown. What that means is uncertain.
This particular genetic material is passed from mother to daughter to granddaughter and so on; the father’s mtDNA is not. This means that if you have a small population with an unusual mtDNA, the probability that it will go extinct in 1,000 years—much less 35,000—is very, very, very high.
It could be as simple as a few females who don’t reproduce successfully or have only males due to random chance. Also, athough we have several thousand mtDNA lineages from living animals, there are millions of dogs and wolves whose mtDNA is unknown. Maybe the sample sizes of living animals are too small and the wolf-dog mtDNA is still out there somewhere. Maybe it is simply extinct.
The standard calculation is that 99 percent of all mtDNA lineages go extinct, so we can’t conclude too much from that. I am not at all worried that the mtDNA information from wolfdogs has not yet been matched in any other group. Also, the entire wolf-dog group may well have gone extinct, with a still-later domestication of wolves into dogs. We just don’t know.
Good Dog: Studies & Research
Seeing eye to eye
How better to spend a chilly winter afternoon than gazing into a pair of warm canine eyes? As it turns out, there’s a perfectly rational reason to do so, one that also suggests how dogs became our “truest companions.”
In a 2015 study reported in Science (“Oxytocin-gaze Positive Loop and the Coevolution of Human-Dog Bonds”), a team of Japanese researchers led by Miho Nagasawa studied the role oxytocin plays in the ancient relationship between people and dogs. Popularly called the “love” or “cuddle” hormone, oxytocin enhances the attachment between human mothers and infants; the longer the two gaze into one another’s eyes, the greater their levels of oxytocin. The practical effect of this feel-good neurological chemical is to stimulate contact. For mother and child, the shared gaze creates a seamless loop of affection and bonding.
Since both dogs and humans use gaze to communicate, the team hypothesized that this same loop might come into play between our two species. It could also help explain how dogs came to take their place in our lives—or, in science-speak, to suggest a reason for our unique “interspecies affiliation.”
The study’s results seem to confirm the hypothesis. In a series of experimental situations, dogs’ “gazing behavior” increased oxytocin levels in their owners, and when the owners gazed back, the dogs’ oxytocin levels went up as well. And, as with human mothers and infants, the amount of time owners talked to and touched their dogs also increased, thus deepening the bond between them.
So, the next time you find yourself engaged in a mutual-admiration session with your co-pilot, remember: it’s not just a pleasant way to pass the time, it’s also part of nature’s grand plan!
Good Dog: Behavior & Training
Dogs who excel often do so in many tasks
Are dogs smart like people are smart? That is the question posed by researchers at the London School of Economics. They weren’t looking into whether dogs are as smart as people, but rather if they are smart in a variety of ways like people are.
When people take IQ tests, they tend to perform at a similar level across various tasks. If they do well in one area, they typically also shine in others. Are dogs the same way, showing a similar structure to their intelligence? By creating a dog IQ test of sorts with several components, the authors of, A general intelligence factor in dogs sought an answer to this question. They study was done with 68 working Border Collies to eliminate breed differences and to minimize differences in upbringing.
The tests performed on the dogs investigated their abilities to navigate barriers to get to food, to determine differences in quantities of food, and to follow a human gesture indicating the location of food. The combined tests took about an hour for each dog.
The general conclusions of the study suggest similarities between the structure of human and canine intelligence. Specifically, just like in people, there was individual variation and dogs who did well on one test were more likely to succeed at other tasks. Dogs who were quick at solving problems were also more accurate.
I think it is very interesting that we have moved away from the idea of “intelligence” as a single factor in humans, but researchers are searching for such a unified concept in dogs. Years ago, people spoke of general intelligence in humans as a separate thing than talents such as social skills, emotional connectedness and athletic or musical or artistic abilities. Now, we are more inclined to discuss people’s emotional or social intelligence or musical IQ, and more likely to discuss factors that are included in intelligence (like problem-solving ability) by being specific about them.
The main result of this study—that certain abilities in dogs such as negotiating detours, assessing quantities of food, responding to human gestures and solving problems quickly tend to be linked—is very interesting. I wish the authors would have focused on the links between the specific tasks they studied instead of generalizing to the point of putting every ability into one category called intelligence. What is going to happen if future studies suggest that a particular trait or ability is found to have no correlation to the others? Will it be considered irrelevant to intelligence, in its own special category or will it pose a problem to the concept of a general intelligence?
That said, I consider this an excellent study. It clearly shows that some individual dogs consistently have better success when asked to solve problems to accomplish various tasks. Very few studies have looked at how dogs differ from each other in this way. More studies on individual differences in cognitive ability are needed and I look forward to learning more about how dogs’ minds work as researchers continue to pursue studies comparing individuals’ abilities.
Good Dog: Studies & Research
Superior Senses: Hearing
Floppy, folded, small, large—dogs’ ears come in many shapes, but they all serve the same purpose: as funnels for sound. Did you know that at least 18 muscles work to tilt, raise and rotate these furry appendages, helping the dog identify and capture sounds from different directions? Here are a few fast facts about canine ears and hearing.
Sources: Alexandra Horowitz, Inside of a Dog; Bruce Fogle, Dogs; DVM360.com; hypertextbook.com; aspcabehavior.org
Good Dog: Behavior & Training
Links between canine lateralization, behavior and emotion
A few years ago, dog trainers and behaviorists renewed their love affair with tail-wagging, constantly checking to see whether dogs were wagging their tails higher to the right or to the left. Our awkward attempts at positioning ourselves to observe this behavior were surely entertaining to others. Why were we so eager for the information conveyed by these asymmetrical tail wags? Because they indicate dogs’ differential use of the left and right hemispheres of their brains and are, therefore, a window into their emotions.
The study of asymmetrical tail wagging that prompted our collective interest (Quaranta et al. 2007) found that differences depended on what inspired the wags in the first place. Dogs wagged higher to the right when greeting their guardians. The same right-side bias was seen in response to unfamiliar people, although the wags were lower overall. In response to cats, there was little wagging, but it was still higher to the right. In the tests, the only stimulus to which dogs’ wags had a left-side bias was an unfamiliar, confident dog.
Left or Right?
The left hemisphere is activated when the brain is processing positive experiences associated with emotions such as happiness, affection and excitement, as well as anything familiar. The right hemisphere takes precedence when processing sadness, fear, other negative emotions and novel things.
This link between emotions and sides of the brain came to light in studies of humans. Ahern and Schwartz (1979) found that people who were asked questions that elicited either positive or negative emotions responded in accordance with this principle. They looked to their right (showing left brain hemisphere involvement) in response to questions that elicited positive emotions, but looked to their left (showing right brain hemisphere involvement) in response to questions that evoked negative emotions.
Individuals—canine or human—who favor the left paw or hand more often use the right hemisphere of their brain, while right-pawed and right-handed individuals have a more active left-brain hemisphere. Studies have shown differences between right-pawed and left-pawed dogs. They have also revealed that dogs who are ambilateral—who don’t have a paw preference—are different in predictable ways from dogs who strongly prefer one paw over the other.
Lateralization research, an active area of study, informs our understanding of emotions and behavior. Though dogs and people are common study subjects, similar patterns have been found in fish, amphibians, reptiles, birds, and primates and other mammals.
Determining Paw Preference
Strength of Lateralization
Batt et al. (2009) showed that dogs with stronger paw preferences were bolder and less cautious than dogs with weaker paw preferences. They were more confident, less prone to arousal and anxiety, quicker to relax or become playful in new environments, and exhibited calmer responses to novel stimuli and strangers. It turns out that we humans are similar to our best friends in this regard: People with weak hand preferences are more likely to suffer high anxiety levels and are more susceptible to both PTSD and psychosis than those with a strong handedness.
Just as being right-pawed predicted guide-dog training success, dogs with a strong lateralization (either left or right) and a low rate of using both paws in the Kong test fared better in these programs (Batt et al. 2008). The authors hypothesize that this may be because strongly lateralized and right-pawed dogs are less likely to experience high reactivity and distress responses, which are detrimental to success as a guide dog.
Dogs also turned left in response to images of cats and snakes but not to images of dogs. With repeated presentations, there was a change toward right-turning behavior, indicating that the left side of the brain and its associated positive emotions were involved. This suggests that novelty may be a factor in fear and other intense negative emotions that tend to be processed by the right side of the brain.
To understand the role of lateralization in processing olfactory stimuli, it is essential to know that each side of the brain processes the information received on the same side: the right nostril goes to the right hemisphere, the left nostril goes to the left hemisphere. Dogs started to sniff novel but non-aversive stimuli (food, lemon, dog secretions) with their right nostril and then shifted with repetition to using their left nostril, showing a change from negative to positive emotions. When presented with adrenaline and sweat from their vets (really!), dogs demonstrated a consistent bias toward the right nostril, suggesting that their emotions started, and remained, negative in response to these odors (Siniscalchi et al. 2011).
* * * * * * *
Love and understanding compound one another with our dogs, and lateralization is a case in point. A dear dog friend of mine is strongly right-pawed; it was pitiful to watch him attempt to learn to give a left high-five, or use his left paw to hold his Kong when he briefly had a bandage on his right paw. I used to find how hard it was for him to do anything with his left paw somewhat comical. Now I understand that this trait is part of the package that makes him the unflappable, happy, don’t-care-about-the-power-tools-running-all-day-during-the-kitchen-remodel, playful and exploratory, nothing-fazes-him kind of dog I love so much. I’m honored and overjoyed that when he greets me, his tail wags are as one-sided to the right as the rest of him.
A romp at the dog park, a run along a trail, a walk around the neighborhood--we know how important it is to get our dogs out and about. But how often do we think about exercising our dog's brain? And really, why should we think about it at all?
Recently, I listened to an online seminar offered by Karen Overall, MA, VMD, PhD, DACVB, CAAB, and board certified Applied Animal Behaviorist, that provided several answers to this question.
Dr. Overall starts out by making the interesting point that it's very likely that dogs co-evolved with humans, which was made easier because both species have similar social systems that rely on work and problem-solving. Dogs still need to problem solve but in today's world, probably don't get enough opportunities to do it, which is why we need to provide them with mental stimulation as well as physical exercise.
She then discusses some of her research and shows videos of dogs working a puzzle box designed specifically for one of her projects; she also analyzes what the dogs' performance indicates about their emotional state.
The takeaway is that stimulating a dog's brain by engaging his capacity to problem solve improves both his physical and mental health. It's also key to helping dogs with behavior problems learn new ways to respond to stress.It's science nerd nirvana, a combination of theory and practical advice (most of which comes at the end in the Q&A segment).
The seminar is titled From Leashes to Neurons: The Importance of Exercising Your Dog's Brain for Optimal Mental and Physical Health, and you'll need to register to listen in (registration is free). Get started here: http://vetvine.com/article/192/akcchf-human-animal-bond-event
Good Dog: Behavior & Training
Dogs vary in their view of the world
If you think all dogs are cheerful, upbeat and excited about what life has to offer, you’ve either interacted exclusively with optimistic dogs, or you haven’t noticed that some dogs are a little more on the “food bowl half empty” side of the personality spectrum. Not all dogs are quite as happy-go-lucky as we humans generally assume.
The idea of individual personalities in dogs is hardly stop-the-presses news anymore, but studying such differences in dogs is still a fruitful area of research. In a 2014 study published in PLOS, a group of scientists studied judgment bias in dogs to investigate individual tendencies to view the world optimistically or pessimistically.
To study dogs’ expectations of the world, they trained them to associate different sounds with different outcomes. One sound let them know that touching a target would result in receiving the preferred reward of milk. The other sound, two octaves apart from the milk sound, indicated that they would get the less desirable reward of an equal amount of water. The correct response to the water tone was not to touch the target. Once dogs could easily distinguish between these two sounds, the real test of their personalities began.
Trained dogs were given a tone that was between the two trained tones, and their response was observed. Dogs who reacted to the ambiguous tone by pushing the target in anticipation of milk were considered optimists. They expected good things to happen. Dogs who failed to respond to the ambiguous tone were considered pessimists in that they did not have an expectation of good things. They were not filled with the hopefulness of the optimists in the study. This study allowed researchers to determine whether individual dogs have the expectation of positive outcomes or whether they expect negative outcomes.
Some dogs would respond to ambiguous tones even if they were more similar to the water tone than to the milk tone. These dogs were considered extreme optimists. Overall, researchers found that more dogs were optimists than pessimists. I find that reassuring since it matches the way most of us view dogs.
What do you think this test would reveal about your dog?
It looks like we soon may be able to chalk up another win for the power of the canine nose.
In a recent UK National Health Service (NHS) preliminary study, trained dogs were able to sniff out prostate cancer 9 out of 10 times, making them a more accurate predictor than the standard (but controversial) Prostate-Specific Antigen (PSA) screening test, which has a high "false positive" rate.
For men of a certain age, the prostate goes from a background to a foreground worry. The walnut-sized gland circles the neck of the male bladder, and when it starts causing problems, there can be a number of reasons. The most serious is cancer. To arrive at a definitive diagnosis requires a biopsy, which--like any surgery--comes with its own risks. And this is why the "false positive" rate matters: in order to make a decision to go ahead with a biopsy, a man needs to have a pretty good idea that it's needed. The more accurate the screening, the fewer unnecessary biopsies.
Based on the success of the preliminary study, the NHS has recently authorized clinical trials to more definitively test the canine ability to identify prostate cancer. Dogs trained by the group Medical Detection Dogs will be taking part in the upcoming trials. This group, co-founded by by Dr. Claire Guest, was among those profiled in Barbara Robertson's Wonder Dogs article; click on over to read more about it.
Wellness: Healthy Living
Investigating the microscopic worlds in our dogs may reveal pathways to better health.
The microbiome is the invisible world of the hundred trillion bacterial, viral and fungal microbes that live on us and in us—on our hair and skin, behind our ears and inside our eyelids. The bulk of these miniscule microbes are good guys, gut microbiota that congregate in the digestive tract, where they bolster the immune system, manufacture vitamins and digest food to generate nutrients and energy.
Microbial equilibrium is a delicate balancing act, and a broad spectrum of inflammatory and autoimmune diseases is linked to having too many microbes—or too few. For example, researchers know that significantly lower bacterial diversity is found in both people and dogs with chronic inflammatory bowel diseases.
Teasing out the biological interaction of trillions of miniscule microorganisms that colonize the body, and the role they play in well being, is a new frontier. Will it be a watershed moment in veterinary medicine? Scientists are hopeful. The human microbiome has become a hot topic in biologic investigations, and canine research is fast catching up, much of it inspired by the success of the Human Microbiome Project, launched in 2007 by the National Institutes of Health (NIH). Using stool and tissue samples to isolate microorganisms, researchers are mapping the diversity and normal profile of the human microbial community.
Another undertaking, the Human Food Project, invites the public to submit personal and family microbial samples along with samples from family dogs to better understand how a person’s microbiome compares to that of animals living in the same environment. (The project’s dog segment has been discontinued.) The analysis centers on the anthropological co-evolution of humans, animal and plant microbes to understand modern disease against the backdrop of our ancestral/microbial past.
It’s all about dogs at Companion PBx, a new startup that primarily targets the canine digestive tract. Its goal is to build a cumulative gut flora database and develop dietary products customized for dogs’ digestive health. In January 2015, the company launched a Kickstarter campaign to raise money for construction of the database.
According to Companion PBx Chief Science Officer Kelly Scott Swanson, PhD, who’s on the faculty at University of Illinois, Urbana-Champaign’s Department of Animal Sciences, “By sequencing the microbes in your pet’s sample, we obtain a fingerprint of the microbial community in your pet’s GI tract.”
Microbes in Common
Affected by age, environment, ancestry, evolution, genetics and diet, microbial communities vary widely between species and across individuals within a species. A recent study suggests that our housemates—including the family dog—may also affect the composition of our personal microbial signature.
If you and your significant other kiss, hug and/or share a bed with your dog, the three of you have more in common than you think. A study conducted by researchers at the University of Colorado, Boulder, revealed several similarities: Adults who share a dog have more similar mouth microbes than those who don’t. Dog-owning families have more diverse and different microbial colonies than dogless households. Parents tend to share more kinds of mouth bacteria with their dog than they do their children. And children raised with dogs have a wider variety of microbes than dogless kids (Song et al. 2013).
Whether these spit-swapped microbes serve a purpose or are just passing through is not clear. But research shows that children raised with dogs are less likely to be afflicted by eczema (Epstein et al. 2010) and asthma (American Society for Microbiology 2012).
The notion that microorganisms in the canine gastrointestinal tract might have unique properties is not new. Early Romans understood the medical value of a well-run therapy dog program. Health temples, the ancient equivalent of modern-day outpatient clinics, were staffed with live-in cynotherapists, gentle dogs who wandered about the grounds greeting patients and licking wounds. Were the dogs healing only psychosomatic injuries? Time and additional research funding will tell.
The idea that our microorganisms may to some extent be collectively beneficial is intriguing. People and dogs have been exchanging microbes for at least 30,000 years, since the first little cave girl kissed the first proto-dog puppy smack on the muzzle. That’s a long history of sharing. It’s possible that our microorganisms are at least symbiotic, and perhaps even played a role in the dramatic domestication of the dog.
Theoretically, many thousands of years ago, a population of carnivorous wolves or ancient proto-dogs (depending on where you stand in the dog-domestication debate) transitioned from a meat-heavy diet to one laden with grain, a consequence of the agrarian revolution.
Scientists know that the acquisition of a new diet is a fundamental driver for the evolution of a new species (Dale, Moran 2006). When species transition from carnivorous to omnivorous diets, the gut microbial community co-diversifies with the host and drives further evolution (Ley et al. 2008). As human diets changed, so too did those of Canis familiaris. Over time, as we incorporated these unique animals into our daily lives, we continued to reshape them.
In humans, autoimmune and inflammatory diseases are on the increase. Scientists can’t verify a similar pattern in dogs because epidemiological studies are rarely conducted in veterinary medicine. Additionally, many autoimmune conditions are diagnosed based on the patient’s subjective description of symptoms.
But this is not the case with itchy skin. Dogs who scratch themselves incessantly are highly likely to have allergies. When researchers compared microbial colonies on the skin of healthy dogs to those of dogs with allergies, they found that non-allergic dogs have much richer and diverse skin microbial communities (Hoffmann et al. 2014).
But when it comes to proving causality, scientists wisely err on the side of caution. It’s not understood if a change in the microbiome causes certain conditions, or if it occurs as a consequence of the conditions. Nor is it absolutely clear that more diversity is better than less. At this point, scientists cannot say with confidence exactly what a healthy microbiome should look like in the dog.
Moreover, what seems logical may not be so. For instance, anyone who has lived with a poop-eating pooch has wondered why some dogs do and other don’t. Are coprophagic dogs seeking microbes lacking in their gut? Surprisingly, research involving mice suggests that this might not be the case; coprophagia in germfree mice is the same as in conventional lab mice (Ebino et al. 1987).
Other questions arise: Are the microbiomes of individual dog breeds more similar to each other than they are to those of other breeds? And could these isolated microbial communities drive breed-specific ailments?
Jan Suchodolski, DVM, a Texas A&M veterinary medical and biomedical sciences researcher who studies dog and cat gastrointestinal diseases, says that this doesn’t seem to be the case. As he noted, “So far, we do not have any clear evidence that gut microbiomes are more similar within breeds. Environmental influences such as age, diets and antibiotics, and especially the effects of GI disease, are larger than any breed effect.
“It may be possible that we missed an effect, as we have not evaluated thousands of animals. But if there were a breed effect, it would probably be very minor. Even within puppies of the same litter, the microbiome shows huge inter-animal variation, so the animal effect is much stronger than any other effect.”
Idiopathic canine inflammatory bowel disease (IBD) is a gastrointestinal condition in which the digestive tract is chronically inflamed. Symptoms include vomiting, diarrhea and weight loss. Dogs with IBD have significantly lower bacterial diversity as well as microbial communities that are distinct from those of healthy dogs. In 2014, Dr. Suchodolski and his colleagues conducted a study of 22 companion dogs, half of whom suffered from idiopathic IBD (Minamoto et al. 2015). They wanted to know if traditional treatments—steroids and special diets—directly or indirectly created a more robust microbial community.
After treatment, the sick dogs felt a lot better. However, there was no change in their gut microbiota. The researchers concluded, “This study demonstrates intestinal dysbiosis [microbial imbalance] and altered serum metabolite profiles in dogs with IBD. But medical therapy doesn't seem to affect the intestinal dysbiosis.”
It could be that, rather than triggering the condition, microorganisms are compromised by it. Researchers also suspect that biological environmental stresses are involved in ways not yet understood. Dr. Suchodolski added, “It may be that we need longer follow-up periods of treatments to see potential improvements. Another reasonable theory is that with the current standard therapies—for instance, immunosuppression—we just control clinical signs, but the underlying etiology of the disease is ongoing.”
When it comes to treating dogs for myriad problems, vets often prescribe antibiotics, and for good reason: antibiotics save lives. But the war on infection sometimes puts good bacteria in the line of fire, too. When assaulted by repeated antibiotic use, some classes of gut bacteria struggle to recover. If the affected bacteria play a pivotal role in autoimmune health, overuse of antibiotics may coincide with a decrease in healthy autoimmune responses.
Antibiotics are not the only culprits. Scientists suspect that in human births, Cesarean deliveries may contribute to an increase in autoimmune weaknesses as well. In a vaginal birth, the fetus departs the womb without a single microbe but acquires them by passing through the mother’s birth canal. By the time the newborn takes his first breath, he is covered with colonies of bacteria that kick-start his immune system, establish a healthy digestive tract, help shape his growing brain and even protect him from psychiatric disorders. C-section babies start life without the microbes they would have picked up from vaginal delivery, suggesting that the colonization of the newborn might be delayed (Jakobsson et al. 2014).
Medical disorders connected to non-vaginal delivery and the slow introduction of protective bacteria have not been studied in the dog. Considering that a number of breeds with exceptionally flat, wide skulls—such as the Boston Terrier, French Bulldog and Bulldog—must have their pups delivered via C-section, it’s an area that deserves further study.
Or is diet the problem? Commercially manufactured dog chow was introduced in the U.S. in the mid-1920s. By the 1950s, processed dog food like Friskies, Sergeant’s and Purina were widely available through local grocery stores. Today in the U.S., we spend more than $10 billion a year on commercial pet food. The question arises: has the increase in autoimmune diseases paralleled the rise in popularity of processed dog food?
Because veterinary practices typically don’t collect this type of empirical data, the answer is, at best, a guess. But many dog owners think so, and have eliminated or cut back on processed foods in favor of raw meat and vegetables. However, as of now, there is no definitive evidence to show that fresh foods modulate the gut microbiota.
Sophisticated DNA sequencing technology has opened up the invisible world to scientific scrutiny. But determining its impact on the host species is difficult and time-consuming. Researchers need to locate and identify a microbe’s fingerprint, then remove a sample and grow it in a culture, a process especially difficult with shyer microbes that are destroyed by oxygen or stomach acid.
To figure out why we get sick and the role microbes play in illness, researchers must first determine how these trillions of organisms interact with each other. And the fact that scientists can prove a problem exists doesn’t mean they know how to fix it.
Developing therapeutic dog foods that target specific vulnerabilities may help, but will take time to develop. Although the probiotic movement may oversell their benefits, probiotics (friendly bacteria like those that live in the gut) are effective in some cases. And prebiotics, foods that encourage growth of good bacteria already present, may help as well.
The University of Pennsylvania School of Veterinary Medicine (Penn Vet) is recruiting dogs with acute symptoms of diarrhea and/or vomiting for a new clinical trail that will evaluate the role of the intestinal microbiome—the community of “good” bacteria that live in the gut—on chronic gastrointestinal diseases. Therapy will include simple diet change, treatment with antibiotics or combination therapy with steroids for more complicated cases.
Penn Vet researchers anticipate that their study may reveal how gut microbiota influence and respond to treatment, which in turn could lay the groundwork for future projects using treatments such as prebiotics, probiotics or fecal transplants (transferring “good” microorganisms from a donor’s healthy stool to the patient’s gastrointestinal tract). According to Research Assistant Professor Dr. Daniel Beiting, “Whereas past studies have used a single method to sequence bacterial DNA, the Penn Vet study will use a more sophisticated approach called metagenomics, generating a much more comprehensive catalog of bacteria in the stool and providing insight into what they might be doing.”
Penn Vet is currently looking for dogs with chronic gastrointestinal problems. People interested in enrolling their dog in the study—Evaluating the Role of the Microbiome in the Resolution of Canine Chronic Enteropathy—should email Penn Vet’s Veterinary Clinical Investigations Center at email@example.com, or call (215) 573-0302.
Future possibilities are exciting. In the meantime, kiss your dog. It’s good for you in more ways than one.
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