10 Amazing Things Dogs Can Sense

Honeybees are vitally important, and not just for their honey — they're important pollinators of food crops. But in recent years, there's been a serious decline in the honeybee population. Among the biggest culprits are bacteria called American foulbrood.

The bacteria's microscopic spores spread quickly from beehive to beehive, killing the bee larvae. The spores can survive for many years. Fortunately, if the bacteria are detected early enough, antibiotics can save the hive.

For decades, many states have had bee inspectors on their payrolls in an effort to keep the bacteria under control. But inspecting beehives for bacteria is a time-consuming job for humans, who must open each bee colony to look for the infection. A human bee inspector might take a full day to inspect 50 beehives. [source: Coren]

Fortunately, with proper training, the same keen sense of smell that enables dogs to detect illegal drugs can be used to nose out the foulbrood bacteria. In the late 1970s, the state of Maryland started using dogs to help human inspectors. A well-trained dog can inspect as many as 100 beehives in less than an hour by sniffing. [source: Johnson]

The canine inspector walks along rows of beehives, sniffing for the bacteria. If a dog smells the foulbrood, it sits in front of the hive to alert its handler. Of course, the job has its hazards: A bee sting can be painful for a dog's delicate nose. Fortunately, inspections can be made during the cool months when bees are less active.

Humans don't have any trouble smelling an angry stinkbug. But insects with less noticeable odors often go undetected by humans until they've done their damage.

Increasingly, pest-control companies rely on trained dogs to help them find termites and bedbugs, for example. In the case of termites, humans sometimes see the damage the pests have caused to a structure, but have trouble finding where the termites get in. That's when a termite-sniffing dog can save the day by finding the entry point as well as bugs and their eggs.

As the bedbug problem grew in the U.S. early in this century, people turned to dogs for help against them. One problem with bedbugs is they are so tiny — about the size of an apple seed — that they can go unseen until they reproduce enough to become a problem. In urban areas, there's a growing demand for bedbug inspections in real-estate transactions.

By 2010, a bedbug-sniffing beagle named Roscoe working for an environmental company in New Jersey had gained considerable fame, even appearing on network TV shows. But as the use of bedbug-sniffing dogs grew, so did controversy over their effectiveness, as reports came in about dogs raising false alarms.

Research has shown that dogs can smell bedbugs and termites, but a lot depends on how well a dog has been trained and how good its handlers are.

In the late 1990s, Jose Peruyero, a former police dog handler, began collaborating with entomologists at the University of Florida to improve training for bug-detecting dogs [source: UFL]. The National Entomology Scent Detection Canine Association (NESDCA) has been formed to set standards for insect-snigging pooch programs, and some states are considering certification for pest-control dog teams.

Stay tuned on this one.

Since ancient times, people have believed that dogs can sense earthquakes before they happen. Early Greek records describe dogs howling before an earthquake rocked the city of Helice in 373 B.C.E. In Japan and China, dogs and other animals are a vital part of the early warning system.

Many modern skeptics discount the idea that dogs can tell when an earthquake is about to happen. Dogs don't have any extra-sensory perception or magical powers, they argue. Geophysicists at the U.S. Geological Survey have said that despite many anecdotes, they have not found a strong connection between specific dog or other animal behavior and earthquakes [source: Mott].

But Stanley Coren, the author of many books about dog intelligence and behavior, suggests that the explanation for dogs' ability to sense earthquakes has nothing to do with anything supernatural — and everything to do with dogs' keen hearing. Coren's studies suggest that dogs can hear the movements of rocks underground that happen just before earthquakes.

Dogs can hear sounds out of the range of human hearing, and they can hear sounds farther away than people can. Coren even found that dogs with floppy ears heard the seismic sounds before the earthquake less than did dogs with pricked ears [source: Coren].

It's possible the skeptics are looking for the wrong evidence. Not every dog will react the same way when it senses an earthquake. Some bark or howl; others may pace or stay close to their people. People who are close to specific dogs are likely to know more about what their behaviors mean.

Many dog owners have no trouble believing that their pets can sense thunderstorms. It's all too common to be awakened at night by an anxious dog only to hear thunder half an hour later. Stories abound about distressed dogs alerting people that a tornado is coming. If your dog is trying to crawl under the couch, it may be time to take everybody to that interior room without windows.

For those who know what to look for, dogs also may predict other changes in the weather, such as a snowfall or the approach of rain. With thunderstorms and tornadoes, a dog's keen hearing – about 20 times as good as ours – comes into play.

There are also good, scientific explanations for why a dog can sense other changes in the weather. Dogs have much keener hearing than humans, of course, but their other sense are also sharper than ours.

Before the weather changes, there are changes in barometric pressure and in the static electricity in the air. Some humans are somewhat sensitive to these changes – think people who get headaches when a low-pressure system is on the way. Dogs are even more so. And the sense of smell can come into play as well. Some people say they can smell rain in the air. What they smell is chemical changes in the air; dogs, with their more sensitive noses, smell the changes even more. And dogs can smell the ozone in the air created by the electricity in lightning – even lightning that we don't yet see. Research suggests that the more dogs experience weather changes, the more they learn about the signs they sense. [source: Greco]

People with insulin-dependent diabetes can suffer from dramatic swings in their levels of blood glucose. Often, they can't tell when they're about to have a severe drop in blood sugar that could cause them to collapse and even die. Sometimes, they aren't aware when their blood sugar has dropped to dangerous lows. Not knowing when or where they might experience dangerous drops in blood sugar can make it difficult for diabetic people to live full, active lives.

Over the years, some diabetic people and those who work with them have noticed that dogs seem to be able to sense when blood-sugar levels are low, and sometimes even when those levels are about to drop dangerously.

The answer seems to be that a dog's super-sensitive nose can smell chemical changes in a person's breath and skin that are caused by rapid changes in blood sugar levels. The dog's sense of smell acts much like the breath detector used to check drivers for alcohol in the blood, only it's more sensitive.

It takes training to take advantage of this canine ability. Since 2004, an organization called Dogs for Diabetics (D4D) has been training medical assistance dogs specifically to detect dangerous blood-sugar changes. The dogs learn signals to alert their human companions, or the parents of children with diabetes. The training is expensive, and so are the assistance dogs.

Not everyone with diabetes needs an assistance dog. They are most useful for people who have frequent and unpredictable drops in blood sugar. They can be a great help for parents monitoring young children, and for young adults leaving home for the first time [source: D4D].

A dog's highly sensitive nose can tell it a lot about the people it meets. Medical studies show that dogs can detect at least some kinds of cancer in humans.

Properly trained dogs can detect lung cancer and breast cancer simply by sniffing a person's breath. Dogs have been documented being able to sniff a skin lesion and tell whether it's a skin cancer melanoma.

The dogs are detecting changes in the skin chemistry where the lesions occur. With patients suffering lung and breast cancers, the dogs smell biochemical markers in their breath. Scientists explain that cancer cells give off different waste products than do other cells, and to a dog's keen nose, those products have a noticeable smell.

At their 2014 annual meeting, members of the American Urological Association heard the results of a study that found that trained dogs are 98 percent accurate at detecting prostate cancer by smelling urine samples. Dogs also are being used to detect ovarian cancer by smelling "volatile organic compounds" [source: MNT].

Does this mean that the next time you go for a physical, your doctor is likely to have you screened by a dog? Probably not. But since early detection can be so crucial in surviving cancer, scientists continue to study dogs' ability to sniff out cancer. How does this gift work? How extensive is it? Can it be duplicated with medical instruments? Research in this area is ongoing.

Many people with epilepsy and other conditions rely on seizure-response dogs. Trained as service dogs, these dogs can alert parents when a child has a seizure. They might use a call button or special phone to call for help. They can guard a person having a seizure, protecting the person from injury and even removing objects that might cause harm. They might roll the person into a position in which he or she can breathe.

Some dogs take dealing with seizures a big step further, by sensing when a seizure is about to occur and warning the person, as much as 10 or 20 minutes before the seizure. Estimates are that 10 to 15 per cent of trained dogs can sense when a seizure is about to happen. Sometimes, a dog becomes able to detect an oncoming seizure after having lived with a person as a seizure-response dog for several months.

Scientists aren't sure what the dogs sense. One theory is that a person about to have a seizure has changes in blood or other body chemistry that a dog's highly sensitive nose can smell. A dog might sense a sudden spike in temperature that precedes a stroke. Another theory is that a dog's detail-oriented vision can detect small changes in the person's movements, changes that humans – even the person about to have the seizure – does not notice.

However it works, the dog's warning can alert the person in time to get to a safe place, take medication and/or let others know that he or she might soon need help. [source: SDC]

"Don't let the dog know you're afraid," most of us were warned as children. The idea was that if the dog knew we were afraid, it would take advantage of our fear by becoming more aggressive.

But is it true that dogs can sense fear?

The answer is yes, if you don't get too literal. As far as anyone knows, dogs don't have eerie supernatural powers. There's a scientific explanation for most of the amazing things dogs can sense. Often, that explanation has to do with the dog's nose, its No. 1 way of understanding the world. Dogs have many more scent receptors in their noses than humans do, and their receptors are sensitive to more smells. Some estimates are that dogs' sense of smell is millions of times keener than ours. [source: Horowitz

So, a dog may not read your mind and think fear, but it can smell what happens in your body when you're afraid. Humans sweat when we're stressed. And if we're frightened, our bodies release adrenaline. Our blood starts pumping faster, and we emit pheromones, or chemical molecules that float through the air. Dogs can smell all these fear-triggered human responses.

Dogs' eyes are a secondary sense for them. Because they don't depend upon their eyes for their primary understanding of the world, they pay more attention to individual details than humans do, rather than processing an entire scene. That means that they detect small signals — facial expressions, tensing, varied gait — that tell them we are afraid.

If you're afraid, a dog will know through smells and visual hints. Whether that means the dog will become aggressive depends upon the dog and the situation.

Anyone who's had a canine best friend knows that dogs are attuned to human emotions. If you're sad, your dog will put its head on your knee or snuggle up. It might whine and give you a friendly lick.

Dogs also seem to sense emotions in people they don't know. Take a dog into a nursing home or children's hospital, and it will find those who need cheering up.

Is there a biological explanation for dogs' ability to read human emotions, or is the empathy a natural result of how closely dogs and humans live these days?

The answer is a combination of the two.

The relatively new field of canine neuroscience investigates the workings of a dog's brain. In February 2014, the results of a study by a team of Hungarian researchers were published in the journal Current Biology and reported in popular news media. Using fMRI (functional magnetic resonance imaging), the scientists found that dogs' brains have a small part dedicated to detecting emotions in the voices of humans and other dogs. Humans have a similar brain part that enables them to sense emotions from human sounds, regardless of words. Their findings led the scientists to believe that dogs can tell by the sound of a voice when a person is sad [source: Doucleff]. (There's a fascinating side story about how the scientists got 11 dogs to enter a scanner and stay still.)

Is there more to the story than detecting the sounds of voices? Probably so. In 2004, a Harvard scientists said that his research showed that over the centuries of living closely with and depending upon humans, dogs have adapted genetically, developing a keen ability to read human emotions and intentions [source: Economist].

Whatever the explanation, there's nothing like a sympathetic pooch to lift the spirits.

Can a dog sense when a woman is about to go into labor?

Without a doubt, dogs can tell when a woman is pregnant, partly because they can smell changes in the woman's body as her hormones shift. Later in pregnancy, a dog will sense changes in the way a woman moves, as well as changes in her emotions.

If a dog is around when the woman's water breaks, it will be able to smell the amniotic fluid. If a dog is present when a woman is in labor, it will surely be aware of whatever she's doing and saying.

Those are all fairly obvious. But will a dog know when labor is about to start, before it actually does? Many women say their dog could tell. Visit the comments section on websites for expectant moms, and you'll see plenty of testimonials about how Buster got protective or anxious hours before his mistress went into labor.

The answer may simply be that because dogs live so closely with their humans, a dog can sense emotional changes when a woman's labor is about to start. Also, dogs, with their keen attention to visual clues, may sense subtle physical movements that the woman may not be aware of.

Some people suspect that the anecdotes have more to do with a woman recalling what happened shortly before she went into labor, much as we recall where we were or what was happening when we learned dramatic news.

But who knows? Some dogs can tell when a person with diabetes is about to have a serious drop in blood sugar, or when a person is about to have a seizure. Is it far-fetched to think there might be some small physical change in a woman hours before labor beings, something that humans can't detect but dogs can?