But some animals seem to perform what often seem like miracles, attracting attention for rescuing their owners from dangerous situations, predicting health problems, or making their way home from miles away.
Are these dogs and cats exceptional or are these abilities common among animals? Here's what experts tell WebMD.
Dogs That Detect Cancer
In San Anselmo, Calif., Nancy Best noticed that her dog kept sniffing and licking at her right breast. Doctors found breast cancer.
Research has shown that malignant tissues release chemicals that are different from normal tissue, and “it’s not surprising that dogs can recognize these differences,” says Ted Gansler, MD, MBA, director of medical content for the American Cancer Society.
In multiple studies, dogs have been “intriguingly accurate” at detecting certain cancers by smelling breath or urine samples, Gansler says. The latest research, published in 2011 in the journal Gut showed a Labrador retriever trained in cancer scent detection correctly identified 91% of breath samples and 97% of stool samples from patients with colon cancer.
Still, Gansler and others say much more research is needed on this -- so don't expect your dog to check your cancer risk. You need real cancer screening, regardless of your pet's behavior.
Dogs That Sniff Low Blood Sugar
Donnann Johnson of Lincoln, Calif., credits Pepper, the dachshund/Labrador mix she rescued, with saving her daughter Megan’s life.
Megan has type 1 diabetes. In the first six months after adopting Pepper, the dog woke her up four times in the middle of the night by poking, pushing, or licking her. Each time, Johnson says her daughter awoke feeling dizzy and hungry and realized that her blood sugar level “was getting seriously low.”
Can dogs predict drops in blood sugar? In 2008, Deborah Wells, PhD, a psychologist at Queens University in Belfast, Northern Island, reported on type 1 diabetes patients who said their animals often alerted them to low blood sugar before they noticed their own symptoms. Wells is now studying whether there is scientific evidence to support the phenomenon.
Mark Ruefenacht, a diabetes patient and the founder of Dogs4Diabetics in California, says his group has trained dogs for years to sniff subtle scent changes associated with low blood glucose and alert the person to the problem. He believes any dog with a good nose has the capacity to detect the changes. As with any scent-based training, you can never expect a dog to be 100%, but “they can have a very, very high success rate,” Ruefenacht says.
Lawrence Myers, DVM, PhD, an expert in canine scent detection at Auburn University College of Veterinary Medicine, says it’s “plausible” that dogs would be able to detect the odor associated with low blood sugar, since “they can see and smell all sorts of things we don’t.” However, he cautions that there is “a lack of reliable data ... that confirms that they are doing that, and doing that reliably.”
Dogs That Predict Seizures
Doctors can’t explain it, but some patients with epilepsy report that their dogs are able to tell them when a seizure is coming.
Jennifer Arnold, founder of Canine Assistants in Georgia, tells service-dog recipients there’s no way to train the animals to predict seizures -- only to respond once they occur. But she says about nine out of 10 of the service dogs her organization has placed develop the ability on their own within a year of placement.
“It really doesn’t seem to be terribly difficult,” Arnold says. “Dogs alert in different ways ... Most of them become visibly distressed in some way. They will start licking their person or pawing at them. It’s extremely common for the dog to tug their person toward the ground, as if they want them to lie down.”
The difficult part is determining what the dogs are reacting to, doctors say. Some people believe the dogs are picking up on a scent change, while others speculate they’re detecting an electrical signal or subtle behavioral change that occurs before the seizure, says neurologist Joseph Sirven, MD, editor-in-chief of Epilepsy.com and chair-elect of the Epilepsy Foundation professional advisory board.
“It’s a phenomenon, but we don’t know exactly what’s being registered,” Sirven says. “Evidence -- that’s hard to come by.”
Dogs That Rescue People
In 2008, a stray dog in Argentina captured hearts and headlines when she carried an abandoned infant back to her litter of puppies. A similar thing happened in Kenya three years before, according to media reports.
The fact that a dog might pull a baby out of a dangerous situation “is really not that surprising,” says animal behaviorist Nicholas H. Dodman, BVMS, because it likely recognizes the baby as “a new pack member.”
“Both dogs and cats will go into blazing buildings to get their litter out,” says Dodman, who directs the Tufts Cummings School of Veterinary Medicine Animal Behavior Clinic. “If one of their buddies is lying in the road, it makes sense they would pull them back.”
Some dogs are better at this than others, in the same way that some people are more likely to run into a burning building without regard to their own safety, says ASPCA science advisor Stephen Zawistowski, PhD, a certified applied animal behaviorist.
In other tales of people rescued by dogs, we may be giving the pets too much credit. The dog that wakes his owners by barking when a house catches fire may simply be frightened or upset and wants the owner to do something, Zawistowski says.
“They’re not saying ‘Run, run, run.’ They’re saying, ‘Wake up and save me, something bad is happening,’” Zawistowski says. “We have to put this into context ... We see a lot of cases where pets wake people up and there’s nothing wrong.”
Dogs and Cats Finding Their Way Home From Long Distances
In 2010, an Alabama cat disappeared from his owner’s daughter’s apartment, only to reappear more than two months later at the owner’s home, six miles away. Two years earlier, an Airedale terrier was lost in a car accident in Connecticut and found his way back to his Rhode Island home - a journey of 45 miles.
No one knows precisely how they do it, or just how far the animals are capable of returning from. But domestic dogs and cats are equipped with several skills that allow them to retrace their steps from certain distances, Dodman says.
“Dogs especially, but I’m sure this applies to cats also, are incredible at making mental maps ... They know precisely where they are in space and time. It’s almost as if they have a built-in GPS,” Dodman says. Combine that with “amazing memories” and a sharp sense of smell and hearing, and there’s every reason to expect a dog or cat to wander home from a radius of 5 to 7 miles, he says.
“Could they find their way back home from 100 miles? Who knows? There are reports, and it’s not inconceivable,” Dodman says. But “the farther the distance gets, the less believable it becomes.”
Cats That Do Tricks
A gray tabby named Nora became a YouTube sensation a few years ago after she climbed onto a piano bench and began pressing the keys with her paws.
Her owners, one of whom is a piano teacher, say their piano-playing feline had no prompting from them. But they did give her plenty of positive reinforcement, in the form of laughing, clapping, and lots of praise.
That behavior isn’t all that unusual, says Beth Adelman, a certified cat behavior consultant in Brooklyn, N.Y., who observed Nora’s feats in person.
Cats can learn to play fetch, push faucet handles on and off, and even say ‘Mom.’ The same principles are at work whether you’re training the animal to do a stunt or just encouraging an entertaining behavior, she says.
“The way that you deliberately train a trick and the way you inadvertently train a trick are the same,” Adelman says. “This is true of all animals... You give them attention, you give them food, you use your happy voice, and they’re more likely to do it again.”