Think you know everything about your furry best friend? Think again! Did you know dogs have three eyelids? Or that they sniff out disease in humans? From baby teeth to their incredible sense of smell, dogs are full of surprises. Read on as we reveal 15 fascinating unknown facts that make our four-legged friends even more pawsome. You’ll never look at Fido the same way when you uncover these jaw-dropping secrets dogs have been keeping. Man’s best friend just got a whole lot more interesting!
#1. Dogs Have an Incredible Sense of Smell

We’re all familiar with dogs’ amazing sniffing abilities, but their sense of smell is even more remarkable than you realized. Dogs have up to 300 million olfactory receptors in their noses, compared to only 6 million in us humans.
Their powerful sense of smell is 10,000 to 100,000 times stronger than humans! They can pick up scents that are diluted to 1 or 2 parts per trillion. To give you an idea, 1 tsp of sugar diluted in 2 Olympic sized swimming pools would still be detected by a dog.
Some dogs are selectively bred for their exceptional sense of smell. Beagles have 125 million scent receptors, and Bloodhounds top out at 300 million! With this powerful sniffing ability, dogs can detect drugs, explosives, or contraband; find missing persons; and even sniff out medical conditions in humans.
#2. Different Breeds Sport Different Number of Toes

When you think of a dog’s paws, you probably picture the classic design of four toes with pads on each foot. However, some breeds sport more or fewer than the standard number of toes.
The Norwegian Lundehund breed has six fully functioning toes on each foot, rather than the normal four toes. This unique trait allowed them to grip rocky surfaces and more easily climb while hunting puffins and seabirds in Norway.
Certain breeds like Great Pyrenees and Labrador Retrievers may have extra non-functioning toes called dewclaws on their hind legs. And a few dog breeds are even missing the occasional toe due to selective breeding. Nonetheless, the vast majority of dogs out there have the typical four-toed paws.
#3. Dogs Only Have 1/6th Our Taste Buds

The human tongue contains somewhere between 9,000-10,000 taste buds that allow us to detect sweet, salty, sour, bitter, and umami (savory) flavors. In comparison, dogs only have around 1,000-2,000 taste buds. This means dogs experience a less complex sense of taste than we do.
Dogs’ taste buds are not distributed equally across their tongues like humans. They primarily have taste receptors for salty, sweet, and fatty flavors toward the back of their mouths. Their tongues also don’t have as many sensory receptors for detecting texture and temperature through taste like humans do.
The reduced number of taste buds is likely one reason dogs seem less picky than humans when it comes to food preferences. While humans experience a wide range of flavors from a meal, dogs would get a simpler sensation from the same food. Dogs tend to be most attracted to strong flavors like meaty, fatty, or sugary tastes. They have a higher tolerance and desire for salty flavors compared to humans.
The lesser focus on taste for dogs also explains why smell is much more important to how they experience food. A dog’s sense of smell is 10,000-100,000 times more acute than a human’s. That means a dog can get far more information about a food item through smelling it rather than tasting it. Their evolutionary history as hunters has relied more on scent tracking than on identifying flavors.
So while humans live in a world of complex flavors, dogs experience a simpler sense of taste. This difference in taste bud anatomy and distribution influences their preferences and attitudes toward food. Next time you see your dog gobble down his dinner, remember he’s only tasting a fraction of what you do!
#4. The Collie Has The Keenest Sense of Sight Among Dogs.
The Collie has been bred over generations to have a super keen sense of sight. The wide spacing and angling of their eyes give Collies superior peripheral vision compared to other breeds. Herding dogs like Collies need excellent observational skills to watch over their flock. Their sharp sight allowed them to scan the environment for predators or sheep wandering too far from the group.
In one study comparing human, dog and Collie visual acuity, Collies were found to have much greater sensitivity to visual detail. They could distinguish a 5.5mm gap from 6mm at a distance of 6 metres, whereas the average dog required a 10mm gap.
In another research experiment, Collies were able to correctly identify black shapes from 50 yards away, whereas other breeds could only recognize them at 30-40 yards. If Collie’s sense of sight seems close to supernatural, that’s because it nearly is!
#5. Certain Dogs Can Be Trained to Detect Cancer in Humans
Certain breeds of dogs like Labrador retrievers, German shepherds, Poodles and English cocker spaniels are especially well-suited for cancer detection training due to their acute sense of smell and ability to be trained. There are even organizations that specifically breed and train dogs for cancer detection.
One example is the Cancer Dogs program at Medical Detection Dogs in the UK. They have trained dogs to detect prostate cancer through sniffing urine samples with about 93% accuracy. Another dog named Marine was able to detect colon cancer from stool samples with 91% accuracy.
At Penn Vet Working Dog Center in the US, dogs are trained to detect ovarian cancer by smelling blood samples. A Labrador named Ohana was able to identify ovarian cancer samples with 90% accuracy during training. Other dogs at the center have been trained to identify lung and pancreatic cancer as well.
A German shepherd named Frankie at the Pine Street Foundation in California is trained to detect prostate cancer through smelling urine samples. His detection rate is around 97-98%. Another Pine Street dog named Midas has been trained to detect lung cancer by smelling a person’s breath.
The incredible sensitivity of a dog’s nose combined with their ability to be trained makes them a promising tool for non-invasive cancer screening. While still experimental, dogs may someday provide a fast, relatively inexpensive way to prescreen for certain cancers in humans through odor detection.
#6. Puppies Are Born Deaf and Blind
Those tiny newborn puppies may seem helpless, blindly crawling around. That’s because puppies are functionally deaf and blind during their early weeks of life.
Puppies are born deaf, blind, and toothless, completely reliant on their mother. Their eyes and ears gradually open over the first couple weeks of life. Most puppies open their eyes at 10-14 days old, developing sharper vision by 8 weeks old.
Their ear canals open at around 2 weeks old, allowing sound to register. Puppies’ hearing sensitivity increases steadily until they reach adult levels at around 6-8 weeks old. Just as puppies grow into their oversized paws, they also have to grow into their newfound senses!
#7. Dogs Curl Up When Sleeping to Protect Their Organs
Ever notice how your pup starts off sprawled out when first snoozing, but ends up in a curled up ball by the time they’re in deep sleep? That curled up position serves an important protective purpose for dogs in their vulnerable slumbering state.
When dogs sleep in a curled position with their tail tucked in close, it conserves body heat and protects their organs. Out in the wild, predators could easily spot a sprawled out dog from a distance, whereas a tightly tucked ball is more camouflaged. The tail-tuck also safeguards the sensitive organs in a dog’s abdomen from would-be attackers.
Even though our domestic dogs sleep safely indoors, this instinctive positioning remains ingrained in their DNA. Next time you see your dog curled up in a circle, you’ll know they are unconsciously keeping themselves as safe and cozy as possible!
#8. Certain Dog Breeds Have Serious Eye Problems Due to Selective Breeding
While we’ve selectively bred dogs over generations to have certain desirable traits, it has also led to genetic conditions and health issues in some breeds. One unfortunate side effect of selective breeding for some dogs is a predisposition for serious eye problems and vision loss.
The Bulldog’s signature short, flat face and large protruding eyes makes them prone to painful problems like dry eye, corneal ulcers and cataracts. Pugs often develop eye conditions due to their bulging eyes being prone to dryness and trauma.
Dalmatians are very prone to inherited blindness and deafness. Over 30% of Dalmatians have hearing loss in one or both ears. And English Springer Spaniels commonly suffer from progressive retinal atrophy that causes vision loss. Responsible breeders should screen for genetic illnesses to reduce their prevalence.
#9. Dogs Have a Complex Language of Growls and Barks
Contrary to popular belief, growling doesn’t always signal aggression in dogs. Dogs have an elaborate language of growls to communicate different emotions and intentions. A playful growl signals happiness and draws the attention of other dogs without scaring them off.
Threatening growls warn others away from a valued resource like food or toys. And submissive, appeasing growls calm another dog that seems angry or aggressive. Growling while showing submission signals the dog wants peace and to appease any conflict.
Barks can also convey various meanings. Short rapid barks are an alarm response, while long singular barks signal loneliness. And barks with a rise-fall-rise pattern indicate excitement. Dogs speak volumes without saying a single word!
#10. Dogs Sneeze When Playing to Signal They’re Not Being Aggressive
When you see dogs playing together, you’ll notice they sneeze a lot while roughhousing. This seems peculiar at first, but actually serves an important communicative function.
A sneeze during play signals a dog’s peaceful intentions. It’s their way to say “I’m just playing, this isn’t aggression!” The sneeze helps keep the play mood happy and prevents the dogs from misreading the behavior as hostile.
Dogs instinctively know a sneeze resets the interaction so they can continue playing together without things escalating to a fight. Next time your dogs have a sneezing fit during playtime, you can relax knowing it’s just their way to keep the fun going!
#11. Dogs Have 3 Eyelids, Unlike Humans Who Only Have 2
Dogs win the eyelid number showdown over us humans, with 3 eyelids compared to our 2. Dogs have a third inner eyelid called the nictitating membrane that serves an important health function.
This inner eyelid helps lubricate and protect the eye, distributes tears, and shields the eyes from debris or harm. It extends horizontally across the eye to keep it moisturized and clean. You may occasionally see a dog’s inner eyelid if they get something in their eye or are ill.
In contrast, humans only have an upper and lower eyelid. Our eyes move within our fixed sockets to scan the environment rather than having a protective inner lid. Having three eyelids gives dogs an advantage keeping their eyes healthy and injury-free.
#12. While Chocolate is Toxic to Dogs, Carrots are Perfectly Dog-Safe Snacks
Many dog owners are careful to keep chocolate away from their pets, as chocolate contains the dangerous substance theobromine which is toxic to dogs. But did you know that carrots are entirely dog-approved snacks? Not only are carrots safe for dogs, they are jam-packed with vitamins and nutrients canines need.
A few shredded carrots or bite-sized pieces make tasty low-calorie treats. Carrots offer Beta Carotene, vitamin A, tons of crunch appeal, and even help clean doggy teeth and freshen breath. Raw, cooked, dried or as part of a homemade doggy stew—you really can’t go wrong serving up carrots to your pup.
So next time you want to spoil your dog with a healthy snack or topper for their kibble, grab some carrots. You can reward your good boy or girl without an ounce of guilt! Just be sure to supervise chewing to prevent choking on any large pieces.
#13. Dogs Have a Long-Term Memory Span of Around 5 Minutes
You might notice your dog greeting you at the door as excitedly as if you’d been gone a week—even if you just stepped outside to grab the mail for 5 minutes. Why does it always seem like you’re constantly “new” again to your canine companion? Turns out, dogs have short-term memories spanning no longer than about 5 minutes.
This roughly 5-minute short-term memory applies to meeting and greeting you, receiving food rewards, and performing trained behaviors. But fortunately they have impressive long-term memories of important events, scents, faces, and places imprinted in their brains.
So while they may forget that treat you just gave them, they’ll remember forever their bonding experiences with you, favorite walks, and treasured toys. Your loyal pup will always have you in their heart, even if you briefly escape their short-term memory!
#14. Dogs Have Over 10 Vocalizations Compared to Humans Who Only Have 5
Dogs may not be able to speak our language, but they have a complex vocabulary of their own. The typical human uses only around 5 distinct vocalizations: laughing, crying, yelling, cooing and hushing. Dogs use over 10 vocal communications, from basic barks and growls to more intricate sounds.
Recent studies found dogs use distinct types of barks, growls, whines, whimpers, yelps, sighs, howls andother specialized sounds to convey a wealth of meanings. Combining various tones, pitches and frequencies allows them to express a spectrum of feelings and intentions to other dogs and their human companions.
Dogs perceive our language intonations and emotional tones even if they don’t grasp our literal words. Next time your dog “talks”, listen closely, as they may be telling you more than you thought!
#15.Dogs Are As Smart As 2-Year Old Children
Research shows that the average dog is about as intelligent as a 2 to 2.5 year old child. Dogs are capable of understanding up to 250 words and gestures. Intelligent breeds like Border Collies can learn over 1,000 words. Dogs also understand cause and effect relationships in their environments.
The Bottom Line
Who knew our canine companions were hiding so many surprises? Underneath that familiar furry face is an animal still retaining much of its ancestral wildness and mysteries. We’ve only begun unlocking dogs’ genetic secrets and decoding their purposeful vocalizations.
As one of the most historically significant domesticated species, dogs display a fascinating blend of inherent instincts and selectively bred traits. By better understanding our loyal pups’ true capabilities and needs, we can nurture even stronger bonds and provide the best possible care.
The next time you look your dog in those loyal, loving eyes, remember the superhero vision, human-like emotions, and other hidden talents housed within. Your furry friend has many secrets yet to be uncovered! Our dogs never cease to amaze us – here’s to embracing the joy of discovering something new about them every day.