Why do dogs lick people? And answers to 50 other canine questions

Dogs wag their tails in part to show excitement, but it goes much further than that. Canine tails are comprehensive communication tools that convey a wide range of emotions, depending on how they're wagged and in what direction. For example, a 2007 study referenced in Live Science suggested tail-wagging to the right may indicate positive emotions (as dogs access the brain's left hemisphere) while leftward-wagging tails hint at negative emotions (accessing the right hemisphere). Neutral positions suggest a relaxed disposition, low tails suggest submissiveness, and high tails indicate arousal or aggression.

The name Fido comes from the Latin word "fidelitas" meaning faithful—an apt description for many pooches. There have also been two famous dogs named Fido, which has helped propel the name to fame in popular culture. First was Abraham Lincoln's dog—the first presidential dog to ever be photographed. Later, an Italian dog named Fido became famous during World War II when his owner was killed in a factory bombing at work. According to local newspapers, Fido went to the bus stop every day for 13 years waiting for him to return, and the town erected a statue in his honor.

According to certified dog trainer Victoria Schade, dogs aren't actually smiling in the human sense of the word when they turn their mouths upward. However, dogs do have their ways of communicating happiness. "The canine equivalent of a smile is a bouncy body, a loose tail wag, and a facial expression with soft eyes and a relaxed mouth and ears," Schade told PetMD. It is also likely that some instances of smiling are adaptive behavior, learned from positive reinforcement they've received when making the expression unintentionally.

The Fourth of July makes many dogs tremble. A 2013 study from the Norwegian University of Life Sciences in Oslo, Norway, found that nearly half of all dogs included showed behavioral signs indicating fear when confronted with loud noises such as fireworks, thunder, or gunshots. Some vets believe the fear is learned, perhaps originating from overly quiet environments or traumatic noise-related events early in the dog's lives. Others believe it is a genetic predisposition that can be particular to some breeds.

Chocolate contains an alkaloid called theobromine. Humans can metabolize this chemical compound quickly, but it takes dogs a long time, during which toxic quantities can build up in their bodies. The smaller the dog, the more susceptible they are to potential poisoning. The larger the quantity and higher the theobromine content (dark chocolate has the most), the more severe a dog's reaction will be. It is indeed possible for dogs to die of theobromine poisoning, but more commonly they get extremely sick and a vet must induce vomiting.

Dog whiskers are tiny receptors full of nerve endings at the base of the follicles that send sensory messages to their brains. These receptors help dogs perceive changes in air currents, pick up ground vibrations, and collect useful information about the size and speed of animals approaching or inanimate objects nearby. Certain breeds also use their whiskers to evaluate space and determine if they can fit in certain places or access certain locations.

Dogs are pack animals, and this doesn't change when owners are using the bathroom or engaged in other activities that humans consider private. The instinct to follow owners everywhere arises most likely from their sense of protectiveness and desire to keep their owners in sight at all times—not the desire to watch humans do their business. It also may be a behavior that's been positively reinforced by accident, according to New York veterinarian Dr. Rachel Barrack. "If every time you are with your dog, he gets affection or treats, he's likely to [follow you around] more often," Barrack told Family Handyman.

When dogs are asleep, the electrical activity in their brains show patterns similar to those observed in humans during dreaming states. What's more, there is evidence to suggest that rats dream—a fact that canine psychologist Stanley Coren says means dogs probably do, too. "Since a dog's brain is more complex and shows the same electrical sequences, it is reasonable to assume that dogs are dreaming, as well," he said. Coren, who wrote, "Do Dogs Dream?" said people could observe dogs dreaming about 20 minutes after dogs fall asleep—when a dog's breathing gets shallow, and their muscles start twitching.

A dogs' obsession with peanut butter is probably linked to the salty taste, along with the rich smell, according to Dr. Susan Wynn, a veterinarian at BluePearl Specialty and Emergency Pet Hospital. "Dogs (and people) are hardwired to seek out certain chemicals that signal a nutrient-rich food, with fat and protein being the primary drivers," Wynn explained to The Dodo. Other factors include the fun nature of peanut butter—it's sticky and can become a game, as well as the fact that it's a "human food" they get to partake in—something that makes it extra special.

Dogs have fur mainly to help control their body temperature, which is why shedding tends to occur seasonally. Although dogs will slough hair throughout the year just like humans, the greatest volume happens in the spring and fall. Spring shedding is the time when dogs abandon their thick winter coat in favor of a thinner summer version. Conversely, fall shedding is the time when they're getting rid of their summer coat to grow thicker, warmer fur for winter. Another function of fur is to protect their skin from the sun, which is any they never lose all of it.

Whether it's a smelly fish that's washed up on shore or a pile of rotting garbage, dogs have a bizarre tendency to roll around in disgusting things—and they seem to love doing it. Dog experts believe this is an instinct left over from the days when their ancestors used to mask their scents during hunts to better sneak up on their prey. Today's wolves still employ this strategy, using animal carcasses or herbivore droppings to hide their smells.

Similarly to humans, dogs indeed get the hiccups—particularly when they're puppies—as a result of their diaphragm muscles spasmodically contracting. It's actually a great way for puppies to alleviate gas or reduce stomach irritation. They generally grow out of this, although adult dogs can get the hiccups, too, especially if they eat or drink too fast. As long as they are occurring in short, infrequent bouts, it's nothing to worry about. If a dog has a prolonged case of hiccups or gets them frequently, owners should see a veterinarian since this can be a sign of something more serious like asthma, pneumonia, or stroke.

Dogs dig in the dirt for many reasons; however, Mary Jo Dilonardo, of Mother Nature Network, boiled it down into five common causes. First, entertainment—they might just be bored. Secondly, they may be trying to dig under a fence to escape. Third, they may be seeking comfort, using the cooler soil to regulate their body temperature or dirt to feel protected. Fourth, they might be burying a toy or bone—a hereditary behavior from their wild dog ancestors. Fifth, they could be searching for moles, chipmunks, or other scurrying creatures.

Domestic dogs are the descendants of wolves, and they can still mate with their ancestors successfully, producing viable offspring. Not only that, dogs can successfully mate with coyotes, too, even though their DNA is more distinct than it is from their wolf ancestors. The resulting offspring are called wolfdogs, coywolves, and coydogs.

Asking whether a dog's mouth is cleaner than a human's is a flawed question because it forces an "apples and oranges" comparison, according to Colin Harvey, executive secretary of the American Veterinary Dental College. Dogs and humans host entirely different sets of bacteria in their mouths, making it impossible to compare them in a meaningful way. That said, some research suggests that both sets of mouths are comparably dirty. A 2002 Harvard study found that human mouths contain about 615 types of bacteria while canine mouths have about 600.

Marking their territory is a primitive instinct that dogs do for the simple reason the name suggests—they're letting other dogs know what's theirs. Scent marking is common among many animals, including monkeys, tigers, wildebeests, wombats, and wolves. It's generally intended just for other animals of their same species, signaling that they've been there and conveying messages such as rank or reproductive status.

Wolves are nocturnal creatures that are most active at dusk (leading some to label them "crepuscular")—and feral dogs tend to follow the same pattern. However, domesticated dogs usually adapt to their owners' sleeping habits, abandoning their ancestors' tendencies in favor of sleeping at night alongside their humans.

Despite the abundance of "dog-shaming memes" and the prevalence of the "guilty dog" face in pop culture, there's little evidence to suggest that dogs can feel guilt. Instead, it is more likely that if a dog expresses a timid face after doing something wrong, they are reacting to perceived anger from their owner. "There have been a number of studies, and it's pretty clear that dogs don't feel or display guilt," Dr. Susan Hazel told The Telegraph. "It's not the way their brains work."

When dogs eat anything that is not food, it can be a sign of a nutritional deficiency, according to PetMD. However, it's often also a sign of pure boredom or odd tastes and not behavior most veterinarians consider concerning. Dog experts have postulated they do it to induce vomiting, improve digestion, or treat stomach worms—essentially self-medicating. However, others refute this, and the theory doesn't have evidence to support it.

There is a widespread notion that dogs are dumb while cats are smart; however, science doesn't back the idea up. On the contrary, a 2017 study published in the journal Frontiers in Neuroanatomy found that dogs have twice as many neurons in their cerebral cortices as cats, suggesting they may have twice the intelligence, too. "Neurons are the basic information processing units," said one of the study's authors neurologist Suzana Herculano-Houzel. "The more units you find in the brain, the more cognitively capable the animal is," Herculano-Houzel told National Geographic.

Similar to the way humans shake hands, butt sniffing is a common greeting for dogs when they first meet each other. It may look odd, but they are smelling tiny glands that convey information about their age, sex, diet, mood, and other personal stats. Dogs have a unique patch in their nasal chambers called Jacobson's organ that helps them microfocus on the scents they're seeking, essentially filtering out the poop smell.

Whether you're calling their name or trying to get them to perform a command, if your dog ignores you, it's likely because of a training issue, not an emotional response. According to Linda Cole, writing for the CANIDAE pet food blog, owners only have a three-second-window for their dogs to associate treats with certain behaviors. If the timing is off, dogs may not understand what they're supposed to do. Another issue is that owners may have inadvertently reinforced their dog's behavior. For example, if someone continues calling their dog after the first time, they're teaching their dogs it is OK to ignore them. Instead, owners should calmly walk over and leash their dogs if their dogs don't respond the first time.

Although there is a common myth that dogs can only see black, white, and shades of gray, this is probably not true—although evidence does suggest that they have partial color blindness. Jay Neitz, a researcher with the University of Washington's Department of Ophthalmology, believes that dogs have dichromatic vision, perceiving color similar to a human with red-green colorblindness. They can see yellow and blue variations, but colors on the red and green spectrums end up gray or brown.

Drooling is a simple excess of saliva that collects in the mouth and drips out the sides. Certain breeds of dogs such as Saint Bernards or mastiffs drool more than other breeds due to all of the extra skin on their faces and snouts—this gives the saliva a place to accumulate. Most of the time, drooling is perfectly normal, but it can also be a sign of things like a fractured tooth, mouth tumor, stomach problems, kidney disease, or another issue. It's important for owners to monitor their pup's drool and see a vet if it's ever out of the ordinary.

Dogs can indeed give birth to just one puppy, although it's much less common than bigger litters. These puppies are called "singletons" and require extra care to socialize due to the behavioral issues that often arise from lack of sibling interaction. The biggest issue is that these dogs often have problems forming bonds with other dogs (even though they do it easily with humans). These dogs may also have a hard time understanding social cues.

Although it seems crazy to think of dogs "watching TV," they can, in fact, perceive the images in a similar manner to how people do and, depending on their personalities, show interest or not. Dogs are especially good at identifying animals on screen, particularly other dogs, and responding to barks or other noises, according to a 2013 study by researchers in France. However, their eyes register images faster so the images may appear to be flickering.

When puppies are born, their moms lick them to keep them clean and well-groomed. This behavior is often associated with affection, and when they lick humans, sometimes they are expressing similar affection. Other times, they may be doing it because people have laughed, giggled, petted them, or otherwise offered praise in the past when they've done it, so the behavior has been positively reinforced. They are also curious creatures and may simply like the taste of a person's skin.

One of the most popular dog myths is that one year in a dog's life is equivalent to seven human years; however, the notion is rejected by experts across the board. As the Wall Street Journal's Carl Bialik pointed out: "If a human year really were equivalent to seven dog years, then people would reach reproductive age by 7, and some would live past 150." Not only that, the rule doesn't take into account the considerable mortality variations among sizes and breeds.

Although water-loving breeds such as labrador retrievers perpetuate the idea that all dogs are innate swimmers, this isn't the case at all. Most breeds are one of three types: natural swimmers, potential swimmers, and non-swimmers, according to Animal Planet. Although personality plays a role, too, these tendencies are strongly associated with certain breeds. Natural swimmers, for example, include breeds like golden retrievers and Newfoundlands while breeds like bulldogs or dachshunds are generally not big swimmers. Others are in the middle and don't take to water naturally but can learn with moderate training and practice.

Dogs can definitely display signs of sadness or disinterest in activities; however, experts are divided on how this compares to clinical depression in humans. PetMD explains that symptoms of depression can often be attributed to a medical condition (an arthritic dog, for example, who doesn't want to take walks due to pain or a dog with kidney disease who doesn't want to eat due to nausea). That said, other times, dogs show clear signs of depression linked to specific events like marriage, divorce, new babies, deaths, or other changes.

Tails serve a variety of purposes people might not think about. First, they help with movement like turning (acting as a counterweight), balancing (providing a counterbalance), and swimming (working as a rudder for stability). They also function as a communication tool, both with humans and other animals, and help spread their scent around.

Usually, when dogs flap their ears, it's because they are trying to hear something better; they also use them for communication. It varies among breeds but generally speaking, ears that are relaxed back mean they're happy while ears flattened back indicate fear. Ears pointed up are on alert, and sometimes they cock their head to the side, too. People will notice that when dogs so this, they are typically turning in the direction of the noise.

The biggest issue when calculating how long owners can leave a dog at home is their dog's bladder. Most adult dogs can wait to pee up to eight hours (though six hours is ideal) and puppies can only wait three hours. There is also variation among size, breed, and overall health. Dogs also need exercise during the day (a quick walk at lunch can make all the difference) and mental stimulation (leave a safe toy that will keep them engaged).

DNA and fossil evidence suggests that domesticated dogs originated in Europe roughly 19,000 to 32,000 years ago. Scientists believe the species branched off from wolves after they began interacting with humans, possibly due to garbage or animal carcasses being left behind. It's likely they began as hunting animals and over time grew tamer, ultimately changing form and becoming the companion pets people know today.

With the exception of small amounts from their noses and paws, dogs don't sweat. Instead, they use panting to lower their body temperature and funnel more oxygen into their bloodstream. This allows them to blow hot air out and suck cooler air in, though it's not very efficient. Dogs also sometimes pant when they are excited, stressed, or eager to play.

Dogs feel basic emotions such as joy, fear, and anxiety, according to Linda Case, author of "The Science Dog." However, these emotions don't have blame associated with them. That means that dogs don't experience anger in the way that humans do. According to PetMD: "What we interpret as anger in a dog is much more likely fear, frustration, disappointment, or annoyance."

Although it's abhorrent to humans, there are many dogs who love to eat poop; there are multiple reasons they do it, one of which is simply liking the taste. Another goes back to puppyhood when they may have seen their mom doing it, mainly if they were in a cage with other siblings. Mama dogs often eat their puppies' stools to keep the space clean or prevent the odor from drawing predators. Other reasons include boredom, stress, hunger, or the desire for attention.

Researchers at the University of California concluded in 2014 that dogs indeed experience jealousy that can be directed at new babies, romantic partners, other pets, or any other creatures that appear to steal the attention of their owners. "Our study suggests not only that dogs do engage in what appear to be jealous behaviors but also that they were seeking to break up the connection between the owner and a seeming rival," said lead researcher and professor, Christine Harris.

The main culprit for wet noses is a thin layer of mucus that dogs secrete to enhance their sense of smell (which it does by trapping small scent particles in the sticky moisture). On top of that, they tend to lick their noses a lot, which adds saliva to the mix. Finally, they have sweat glands in their noses—the only place besides their paws—which produce moisture to help cool them down. This three-part combination is what leads to the perpetually wet state that most canine noses are in.

Dictionary.com calls the word "dog" one of the great mysteries of the English language." Seven hundred years ago, all dogs were referred to as "hounds" (from the Old English "hund"), and "dog" was reserved for a specific subgroup that included mastiffs. No one knows how or why things shifted. Some linguists postulate that "dog" became popular in the same way that "Xerox" and "Kleenex" became generic terms for copy machines and facial tissues.

While some pet owners believe it's OK to leave a dog in a parked car as long as the window is cracked, the American Veterinary Medical Association disagrees. "Your vehicle can quickly reach a temperature that puts your pet at risk of serious illness and even death, even on a day that doesn't seem hot to you. And cracking the windows makes no difference." The AVMA says dogs should never be left in cars, noting a study that found cracking windows has minimal effect on temperature rise. Anna Burke of the American Kennel Club cited 28 states with laws against leaving pets in cars.

It's common for dogs to chatter their teeth when they're nervous or excited. They may also tremble their jaw. In those cases, the circumstances should tell owners why—perhaps dogs start quivering in excitement when their owners pick up a ball or hold a piece of meat. Or maybe they chatter out of anxiety when owners take them to the vet. However, if a dog is chattering their teeth at other times, owners should see a vet because it can also be a sign of oral pain.

Dogs have tear ducts; however, they are meant for clearing debris and shouldn't leak or drip onto their face. If owners notice their dogs appearing to "cry," it's likely the result of an eye infection, allergies, or injury, and they should take their dog to a vet. Dogs do not shed tears due to emotions—humans are the only species that do this.

Scientists don't know for sure why dogs are so much easier to train than cats; however, it's likely that it has to do with them being pack animals, whereas cats are solitary creatures. Not only that, dogs were selected for obedience and social aptitude when being domesticated from wolves. As Slate's Elizabeth Weingarten explained: "Cats were domesticated about 9,000 years ago, and were originally used to hunt mice. It's likely they were selected for their solitary hunting abilities, not for any particular social acuity or inclination to follow instructions. (Dogs, on the other hand, were selected for those very traits)."

It may be hard for humans to understand how a simple walk around the block could bring so much joy, but for dogs, it's the epitome of happiness. There are three main reasons they go so crazy when their owners reach for the leash, according to animal behaviorist and dog trainer Karen London. One, they want to exercise—some breeds need a lot of physical activity (these are the ones who pull their owners down the street at breakneck speeds). Two, they want to sniff everything (these are the dogs who have their snouts buried in the ground the whole time). And three, they want to be social (these are the dogs who spend their whole walk interacting with other dogs).

The answer to this question depends on how one defines "bilingual." In reality, dogs do not speak any language—they simply associate certain sounds with behavior they've been rewarded for. According to SlimDoggy's "Dear Labby" advice column, dogs could be taught multiple words for the same command, but it would be confusing for them. The best way to make it simpler if owners wanted their dogs to respond to two languages, would be to combine verbal commands with hand signals.

There are many reasons dogs like socks, according to Tractive's pet blog. First, they love the chewing sensation—they've been chewing on things since they first started teething, and most dogs find it meditative. Boredom is another common reason. The most significant incentive, however, is that socks smell and taste like their owners. Snuggling up with your scent makes them feel closer to their owner.

Most of the time a dog's bad breath is simply caused by the type of food they're eating or something foul they've ingested such as poop, garbage, or animal carcasses. However, according to Elizabeth Xu of PetMD, there are more concerning things that bad breath can be a sign of, too, such as gum disease, kidney disease, oral tumors, diabetes, or toxic substances they've ingested. If a dog's breath changes or becomes particularly odorous, see a vet to make sure it's nothing serious.

Although it sounds like an old wives' tale, there is evidence to suggest that dogs can indeed smell fear. This is because humans emit pheromones when they're afraid that dogs can detect due to their exceptional sense of smell. Dogs can also pick up on things like sweating or changes in breathing patterns. However, there is no evidence that a dog's any more likely to attack a person if it thinks that the person is afraid. Instead, it will assess its own fear and the threat the person potentially represents.

Dog experts can't say for sure why dogs have a tendency to go so crazy after a bath, but a common theory is that they're experiencing sheer relief. For many dogs, bathtime is a source of anxiety, so running around afterward may be a way to release nervous energy. It's also likely they want to dry off and rolling on the ground is a great way to do that. The most likely reason, however, is that they're trying to get the smell off. With their heightened olfactory system, most dogs find soaps and shampoos intense. As Hannah Gilman of The Dog People put it: "Wanting to smell like poop and dirt and grass is in their DNA."

According to the American Kennel Club, dog saliva contains antibacterial and antimicrobial properties that may help wounds heal faster, though it's a very small amount. Still, the instinct probably originated from this, along with the desire to keep the wound clean. That said, licking wounds can harm more than it helps, so it's best to discourage dogs from doing this.