A Scientist’s Best Friend: The Biology Behind The Human-Dog Relationship

Kristen Blanchard

Originally published April 7, 2015

photo by: kristen thomas

If you had visited Tokyo’s Shibuya Station in the 1920s, chances are, you would have met Hachikō. At the end of every day, this purebred Akita Inu faithfully waited for the train to deliver his master, Hidesaburō Ueno. Yet, when Ueno died in May 1925, Hachikō continued to wait. For the rest of Hachikō’s life (nine years, nine months, and fifteen days to be exact), Hachikō continued to arrive at the station and wait for his owner’s train. Hachikō may be the most famous symbol of canine loyalty, but he is by no means alone. Capitán, a German Shepherd in Argentina, stayed with his owner’s grave for 6 years after he passed. Orlando, a black lab guide dog in New York City, helped save his owner from an oncoming subway train after the man fell onto the tracks. In addition to these “celebrity” dogs, we rely on countless others to help us track missing persons, locate explosives, and help those with disabilities. In return for their services, we love these creatures like no other on the planet. More than one third of American households own a dog, and we spend more than $50 billion annually on our pets. It seems obvious that dogs are man’s best friend, but why does the bond between man and dog seem so different than any other animal?

The answer to this question likely lies in dogs’ unique history. Domesticated dogs, as we know and love them today, evolved from ancient wolves. Unlike the evolution of virtually every other animal species throughout history, the evolution of dogs was artificial. Humans essentially “created” this species by domesticating wolves. Through lucky accidents in different regions throughout the planet, ancient humans noticed that some wolves were more cooperative than their peers. They took in these unusually helpful wolves, cooperating to hunt prey and avoid predators. Biologists believe that by continually selecting for better companions, wolves and humans evolved side-by-side, eventually creating the unique bond between modern humans and dogs.

This strong evolutionary pressure has had significant consequences for the way humans and dogs interact. In the past few decades, scientists have been able to quantify what dog lovers have long understood on an intuitive level; the bond between canines and humans is unique among the animal kingdom. Scientists have demonstrated that dogs are adept at communicating with humans. They can pick up on auditory cues and even physical signals. Dogs understand the meaning behind human pointing, while even our closest relatives, great apes, cannot interpret this gesture. Despite the fact that great apes are more intelligent than dogs, and more closely related to humans, dogs are better at communicating with us. This communication skill goes beyond merely communicating basic information. Some evidence shows that dogs can understand human emotion. Scientists at the University of Veterinary Medicine in Vienna, Austria tested dogs for their ability to recognize human facial expressions. The study found that dogs could distinguish between “happy” human faces and “angry” human faces, even while only seeing part of the face in a photograph.​​

photo by: kristen thomas

What do dogs do with this information about human emotion? Do they “care” if a human is happy or angry? Do dogs have some sort of empathy with their human companions? Scientists have recently tried to answer these questions as well. Contagious yawning (i.e., the tendency to yawn when witnessing someone else yawn) is thought to be a sign of empathy. Contagious yawning is usually more common between people who are emotionally close, than between strangers. Scientists at The University of Tokyo recently investigated whether dogs were also affected by the contagious yawning phenomenon. They found that not only did dogs exhibit contagious yawning when seeing humans yawn; this effect was also more common between the dog and its owner than the dog and a stranger. These results suggest that dogs do display this measure of empathy.

The idea that dogs possess empathy for their human companions is further supported by an interesting study by researchers at the University of Otago in New Zealand. These scientists measured the human physiological response to a baby crying. Humans respond to this trigger with an increase in cortisol and heightened alertness. Fascinatingly, they discovered that a human baby crying affected dogs in the same way. In addition to the increase in cortisol and heightened alertness, dogs also became more submissive. While it is difficult to quantify whether or not dogs “love” their human companions, there is certainly some evidence that dogs have empathy for humans and an understanding of human emotion.

But what about the other side of this relationship? It certainly seems as though humans’ artificial selection of ancient wolves contributed to the way dogs relate to humans today. Were humans also affected by this parallel evolution? Is the bond between humans and dogs hard-wired into us the way it seems to be in dogs? Some recent studies suggest that this evolution was a two-way street; just as dogs evolved to cooperate better with us, we evolved to cooperate better with them. While dogs are adept at recognizing human facial expressions, we are adept at recognizing theirs as well.  A recent study found that even people without any experience with dogs were able to infer a dog’s emotion from a photograph. The fact that even those without dog experience were able to complete this task suggests that this recognition may be innate – an artifact from our co-evolution with domesticated dogs.

Fortunately for us, while dogs may have influenced our evolution, it seems to be worth the tradeoff. Our relationship with dogs provides us numerous benefits as a species. Dogs have a well-documented effect of reducing stress. The American Heart Association has even reviewed the scientific literature and agreed that dog ownership may slightly reduce the risk of heart disease. These health benefits explain why dogs are frequently used as therapeutic aids – they can help soldiers recover from trauma and help children with autism improve in socialization. Thanks to our truly unique interspecies bond, these creatures really are man’s best friend.

Edited by: Bethany Wilson

Let's Talk Bird Brains

Zachary Johnson

Originally published April 3, 2015

photo by: kristen thomas

For a long time we thought that language separated us from other animals, but it’s a bit more complicated than that. Chimpanzees, bonobos, gorillas, and orangutans can all learn sign language. Dogs can use body language, vocalizations, and even facial expression to communicate; and many birds can sing extraordinarily intricate songs to relay information. Even insects and plants can release chemicals that carry important information to their neighbors. So what’s unique about language?

While many animals can “speak,” or produce sounds, humans are uncommon because we can imitate sounds and mix and match them in new combinations to communicate information. This process is called “vocal learning,” and it requires using our vocal chords to imitate sounds. Neuroscientists believe we can do this because we have unique connections in our brains between higher processing areas at the front and motor areas further back that control our vocal chords; other primates—which can’t do vocal learning—don’t have these connections. But humans aren’t the only vocal learning animals, and scientists have turned their attention across 300 million years of evolution to learn more about this unique capacity.

While many birds can sing, their songs are often innate and fixed. Only three lineages possess the unique ability to learn, imitate, and modify their vocalizations based on what they hear: parrots, hummingbirds, and songbirds. Neuroscientists discovered that, like humans, these birds also have unique connections between frontal areas and motor areas controlling the vocal chords. These connections are absent in birds that can’t do vocal learning, like chickens. Both humans and vocal-learning birds that suffer damage to these connections have trouble imitating others’ vocalizations and stringing syllables together correctly. These discoveries had scientists scratching their heads: not only can distantly related birds do vocal learning, but their brains seem to be doing it in a similar way.​​

photo by: kristen thomas

Before diving deeper, it’s important to appreciate the explosion in technological capacity that biological research has witnessed in the past few decades. In 1950, we didn’t know what DNA was. Since then we’ve learned that the genetic codes, or “genomes,” of both humans and birds are made of billions of nucleotides (the building blocks of DNA). We know that every cell in the body contains the same genetic code, but specific kinds of cells turn parts of the genome “on” or “off,” depending on their jobs. Think of pianos; they all have the same 88 keys, but pressing those keys in different combinations and to different degrees results in different chords. Different types of cells in our bodies “express” different combinations of genes and to different degrees; each type has its own “chord,” or its own unique gene expression fingerprint. This is even true across species: gene expression fingerprints of skin, heart, and brain cells in humans may look different from each other, but they look very similar to gene expression fingerprints of skin, heart, and brain cells in other animals.

A team of Duke neuroscientists led by Dr. Erich Jarvis recently took these ideas a bit further: are the gene expression fingerprints of “vocal-learning” brain cells unique? In other words, maybe the animal genetic code can express certain genes to create vocal-learning brain cells across species, just like skin cells or heart cells. The scientists collected tiny samples of bird brain tissue from vocal-learning brain areas in parrots, hummingbirds, and songbirds and analyzed the gene expression fingerprints for each. Next, they tapped into a huge database of gene expression fingerprints spanning the entire human brain. Like forensic detectives, they searched the database for matches. Sure enough, the strongest matches in the human brain database were regions involved in human speech and language.

photo by: kristen thomas

So what? The idea here is that perhaps we aren’t quite as unique as we’d like to think. Scientists have known for a while that the genes guiding human body development are the same exact genes guiding body development across fishes, amphibians, reptiles, and birds. The Duke neuroscientists extended that idea to specific capacities of the human brain. The same genes that guide the development and wiring of areas involved in human vocal learning also guide the development and wiring of areas controlling vocal learning in birds.

It’s important because our language capacity is a huge part of being human, and it has indisputably shaped the course of our history. As biology advances, we will certainly continue to learn more about this unique capacity from parrots, hummingbirds, and songbirds, as well as our other vocal-learning relatives: bats, seals, elephants, and dolphins. In the meantime, the next time someone calls you “bird brain,” consider it a compliment, and take a moment to wonder what other capacities of the human brain and mind might be hidden in the animal genetic code.

Edited by: Bethany Wilson

White Noise Syndrome: An emergent disease battering North American Bat populations

Brilee Coleman

Originally published March 5, 2015

Photo by: Brilee Coleman

If you think bats flying out of haunted houses are scary, imagine finding thousands of bat bodies lying around in the woods one morning. This is exactly what happened when White Nose Syndrome, or WNS, was discovered in 2006, and Myotis lucifugus (little brown bats) were discovered strewn outside of caves in New Albany, New York. WNS is a fatal disease named for a fungal infection found on the noses of hibernating bats. The disease kills bats by causing them to rouse from hibernation prematurely, after which bats wander out into the daylight in the middle of winter, where they die from lack of food and low temperatures. Typically, hibernating bats venture deep into caves where they seek shelter for the winter, called hibernacula. Bats affected by WNS, however, can be found hibernating at the mouths of caves, where temperatures are less stable. These changes in bat behavior have resulted in a loss of 5.7 million to 6.7 million bats of at least 11 different species since the discovery of WNS in 2006. It is believed that WNS was brought to North America from Europe, where the disease is present, but bats are unaffected. Because bats do not travel between continents, it is likely that WNS was transported on the shoes of cavers traveling from Europe to the United States. Since its arrival in North America, WNS has been documented in 25 states and several Canadian provinces.

So how does having a “white nose” result in strange hibernation behavior and death in bats? Hibernating bats have decreased metabolic activity, which allows them to survive the winter by slowly burning off fat stores for energy. Unfortunately for the bats, decreased energy expenditure also leads to suppressed immune function, leaving them vulnerable to infections. Research has shown that WNS is caused by a previously unidentified fungus, Pseudogymnoascus destructans. P. destructans is a psychrophilic (cold-loving) fungus that only functions at temperatures below 20°C, making bat hibernacula perfect environments for fungus growth. Infection of bat tissue with P. destructans leads to more frequent arousals during hibernation, which can result in increased energy expenditure and premature emergence from hibernacula. In the event that bats do survive through the winter, they emerge from hibernation in a weakened state. Because of WNS, even the little brown bat, the most common bat species in the United States, is in danger of extinction.

Why is preventing WNS important?

Bats are critical members of North American ecosystems, and humans benefit greatly from their presence. They are excellent pest control agents, consuming over 1,000 mosquito-sized insects per bat every hour. Many of these bugs are forest or agricultural pests that we would otherwise spend an estimated $3 billion per year paying to control. While bees may get most of the credit for pollination, bats are often-unsung heroes of pollination themselves. If you enjoy having tequila made from agave plants with a side of guacamole made from avocados, thank the bats responsible for pollinating both. Among other plants, bats are also known to pollinate bananas, mangoes, cocoa, and guava. Downstream of initial loss of pest control and pollination of avocado crops, the extinction of North American bat species would likely have major unknown consequences on both economic and ecological health in affected areas.

In addition to having an ecological impact, bats have also served as inspiration for human innovation. Bat Simultaneous Localization and Mapping (BatSLAM) is a radar system modeled on bat echolocation. BatSLAM helps solve the problem of robots navigating and localizing themselves in complex environments, allowing for the development of more autonomous robots.  In addition, biomimetic skins modeled on bat wing properties have allowed for unprecedented flying capabilities in small aerial vehicles, such as controlling various wing shapes and flight modes mid-flight.  Without access to bats for research purposes, these efforts would likely come to a halt.

What is being done about WNS?

There is currently no cure for WNS, although it remains an active area of research. In the absence of a cure, conservation of bat habitats and quarantine of affected caves are critical steps in the effort to prevent the spread of WNS. Current approaches include closing off caves known to be contaminated with WNS and using biosecurity measures to prevent cavers from introducing WNS to caves that are known to be clean. Some things that everyone can do to help prevent the spread of WNS are reporting strange bat behavior, such as flying during the day, to the Georgia Department of Natural Resources, staying out of bat hibernation sites, limiting disturbances to natural bat habitats around your home by reducing outdoor lighting and minimizing tree clearance, and educating others on the many values of bats.  For those interested in actively participating in bat conservation, the Georgia Department of Natural Resources provides information on how to build bat roosting boxes and other volunteer opportunities at their website: http://www.georgiawildlife.com/Conservation/Bats. For more information about WNS, visit: https://www.whitenosesyndrome.org/.

A Murder of Crows

Jadiel Wasson

Originally published October 31, 2014

Photo by: Kristen Thomas and Jadiel Wasson

In the spirit of Halloween, this is a tale of fiction shrouded in fact: A slight exaggeration of the natural ability of the magnificent family of birds known collectively as the Corvidae family.

Imagine this: You are walking alone in the park on a foggy morning with only the pale morning sun to guide you. *Caww*  What was that? *Swoosh.*  Something lands on your bag. You swing it in an attempt to thwart the menacing perpetrator. You move to investigate the damage and realize it is only a crow with a piece of your bagel in its mouth. Your sigh of relief is stifled with the thickening of the air with sounds like the fluttering of thousands of bird wings. A murder of crows has been incited. You immediately make your exit and run to work, afraid of what you have started.

You may have escaped the peril. But what you do not know is that the crows will remember your face.

Crows have an unparalleled ability to recognize and remember faces. To test this ability, a Seattle group of scientists captured and tagged crows while wearing a variety of different masks. Two years later, the crows were able to recognize the masks and remember the misdeeds of the researchers leading to harassment and admonishment of the researchers. This ability to create a negative association with certain people and their behaviors was traced to a particular brain region by another group of researchers. They also observe differential brain regions becoming activated as crows processed human faces. These studies reveal how crows can integrate memory and perception to adapt accordingly to their surroundings.

That night, you are walking home from work, forgetful of your early morning transgression. *Squawk! Squawk!* It begins with one. Then like an avalanche, all of the crows join in a chorus of horror. They dive bomb as only angry birds can. *Crack* You’ve just been hit with a massive object… was that a weaponized nut? It is almost as if the crow who threw it knew what angle and height to drop it from to incur the most damage.

PHOTO BY: KRISTEN THOMAS AND JADIEL WASSON

In fact, it has been well documented that crows can calculate the height and velocity it takes to crack a nut with the least possible damage to the treasure inside. They are even able to deduce environmental clues as once the nut has been dropped on the street, they have the cognizance to wait for traffic to stop in order to jump into the street and collect the spoils. This cold calculation also extends to food storage. Crows, like few other animals, store food away for future use but take it two steps further. In a series of studies analyzing the ability of crows to adjust storage tactics, crows demonstrated not only an ability to deceptively hide food from thieving on-lookers with a “slight of hand” stratagem, they also altered food storage times to account for perishability of food.  These behaviors demonstrate predictive and causal thinking, signs of higher cognition.

Once the crows start using heavy artillery, you realized how much danger you really are in. You sprint home and lock the doors. From your balcony window, you can see that they have tracked you down. They appear to be fashioning small tools from the barbed succulents outside of your apartment, all in the same manner with the same directional tendency.

The ‘handedness’ of crows has been documented to be not only at the individual level but also appears to exist at the social/cultural level in crow species. It hints to brain laterality where there is a division of labor between the two hemispheres, leading to the ability to coordinate actions. It is also important to note that crows do in fact have “cultural” behaviors as it has been documented that crows talk to each in regional dialects.  

Stepped tool making, which has mostly been observed in primates, has been well documented in crows, highlighting their high cognitive function. Studies show that not only can crows decipher which tools would be the most appropriate to complete a specific task (i.e. . choosing proper diameter and length of a stick to retrieve food), they also have the ability to generate these tools. Crows have been documented to independently generate tools in order to complete specific artificial tasks that would not be encountered in the wild. Imagination is considered one of the hallmarks of high cognitive function.

What are they going to do with these barbed tools? The thought is maddening as they fly up towards your balcony window and realize you pet tarantula has been left out for air. As they spear your beloved pet before your eyes, you begin to realize this probably will not end well. They begin to pick the lock to gain access to your apartment. Why are they so smart?

In fact, crows do in fact use small spear-like tools in the wild to forage for insects along the forest floor. Small hook shaped tools are used to gather larvae from trees.

Based on brain to body size ratio, crows have a brain capacity on par with non-human primates. Structurally, their brains are very different while functionally there are certain areas of their brains that are analogous to primates. The region of the brain that is responsible for cognition is enlarged in the Corvidae family compared to other birds. They share the four basic hallmarks of cognition with apes: imagination, flexible knowledge and learning ability, causal learning and prospection. Granted, they cannot pick a lock, but they do have the ability to generalize knowledge and apply what they have previously learned to a novel situation. This allows them to be highly adaptive animals, which is a large reason for their success in urban areas.

*Click* The lock has been picked. The last thing you hear: the fluttering of wings. Who knew how intelligent a bird could be?

What makes crows an interesting paradigm in evolutionary history is that their intelligence is an extreme example of parallel evolution.  Crows have diverged on the evolutionary tree over 100 million years, and as a result have very differently structured brains compared to mammals. Mammals were thought to be the only animals that can possess high cognitive function, thus leading to the idea that their brain structure conferred this ability. Despite the large differences in brain structure, crows are becoming recognized as being just as intelligent as primates. Ultimately, crows represent a great model for how intelligence and cognition can evolve independently throughout evolution.