By Lindsay Lowe
Has your dog ever hidden behind the couch when a storm is coming? Does it seem like your pup can tell when you’re feeling down? Plenty of people swear their canine companions can sense things before they happen, or pick up on changes in the environment that a human could never perceive.
What looks like intuition to us often comes down to a dog’s remarkable sense of smell, but canines can also read our faces and body language, which can help them detect changes in mood.
Here are five amazing things your dog can sense, from oncoming storms to serious diseases.
Dogs Can Sense Your Mood
Dogs can use visual cues to tell when we’re happy or depressed.
“They’re expert body language readers. They can tell the size of your pupils, your posture, your smile,” says Dr. Nicholas Dodman, a veterinary behaviorist and professor emeritus at the Cummings School of Veterinary Medicine at Tufts University.
Dogs have evolved to read our feelings because they rely on a close emotional bond with humans to survive.
“They want to know if we are upset or if we are in a good mood,” says Dr. Carlo Siracusa, the clinical assistant professor of animal behavior at the University of Pennsylvania’s School of Veterinary Medicine. If we are in a good mood, he says, dogs are more likely to interact with us in search of food or attention. But if we look angry or aggressive, that's a warning signal to stay away.
Dogs may also pick up on our elevated stress levels by smelling our sweat, Dodman says. However, he believes they mainly read our moods by observing our body language and facial expressions.
Dogs Can Sense Pregnancy
Dogs may be able to sense that a woman is pregnant—or at least, sense that something major has changed in her body—by sniffing out a shift in her hormone levels, Siracusa says.
Apart from scent cues, pups may also pick up on changes in a woman’s lifestyle. A pregnant woman and her family might adjust their daily schedule or rearrange their house. This would definitely spark a reaction in dogs, who tend to thrive on having a regular routine, Siracusa explains.
Dogs Can Predict Oncoming Seizures
Some dogs can be trained to become seizure detection dogs that alert humans to oncoming seizures.
In the case of hypoglycemic seizures, which are triggered by a drop in blood glucose levels in people with Type 1 diabetes, dogs may be able to smell the different chemicals a human emits during a hypoglycemic episode. In a 2015 study published in the journal Diabetes Therapy, dogs were able to identify hypoglycemia by sniffing human skin and breath samples.
Epileptic seizures are more of a mystery. There is no known odor associated with this type of seizure. Dogs who detect these seizures may be picking up on elevated stress levels and subtle behavioral changes that can precede an epileptic attack, Dodman says.
He cites an acquaintance who “absolutely swears” that her dog often warns her of oncoming epileptic seizures during stressful work meetings.
“You could argue that if her seizures are brought on by stress, what her dog is doing is picking up on signs of stress,” he says. “And if the person goes out and breathes the fresh air, then she’s de-stressed and doesn’t have a seizure. So, [the dog] is not detecting any particular odor that’s associated with the epilepsy, but is actually is picking up on her body language.”
Dogs Can Sense Storms
Your dog starts whining, pacing, and generally “freaking out”—and an hour later, a thunderstorm hits. The ability of dogs to predict oncoming storms is a well-documented phenomenon. Scientists have a few different theories as to why dogs are such great weather forecasters.
Siracusa says that dogs can “definitely perceive” drops in barometric pressure, and they may also detect rising humidity levels and changes in ozone concentration.
Dodman also believes dogs can sense changes in static electricity levels in the air prior to a thunderstorm. He references a study he worked on where dogs were broken into two groups—one group was outfitted with anti-static jackets, and the other served as a placebo group. Though there were only 28 dogs involved in the study and it was not conclusive, 70 percent of dogs in the group that wore the jackets showed a decrease in panic behaviors before thunderstorms compared to only about 30 percent of dogs in the placebo group.
Dogs May Be Able to Sniff Out Cancer
Dogs have such incredible olfactory capabilities that some are even able to alert medical professionals and researchers to different forms of cancer. In a 2013 study in the journal BMC Cancer, dogs were able to identify patients with ovarian cancer by sniffing out chemical compounds in their blood.
Dogs can also be trained to sniff out both lung cancer and breast cancer by smelling a patient’s breath. According to a 2006 study, “ordinary household dogs with only basic behavioral ‘puppy training’ were trained to accurately distinguish breath samples of lung and breast cancer patients.” Dogs have also been shown to detect melanoma and bladder cancer, Dodman says.
However, while the research surrounding dogs and cancer detection is promising, pups can’t detect cancer with 100 percent accuracy, Dodman warns. So, we can’t replace medical testing with canine “sniff tests” just yet.