Honed over thousands of years, wolves evolved powerful hunting skills. In fact, each of their senses developed to augment this formidable prowess. Their hearing is designed to detect the soft footfalls of prey in the distance, and the nearly undetectable rustling of other animals moving through the brush. Their eyesight is built to see tiny, rapid movements we humans would easily miss. Most of all, they were gifted with one of the most powerful senses of smell in the animal kingdom.
Having again descended from Grey wolves several thousands of years ago, dogs inherited these powerful hunting senses, though the average domestic dog no longer relies on them for survival like their ancestors. Though certain land animals have greater olfactory senses, like the brown bear, very few on Earth can come close to comparing!
Olfactory receptors are simply proteins capable of binding to odour molecules, and we humans have roughly 400 different types containing 5-6 million cells, able to detect around 1 trillion different scents (SIRC). A rabbit, desperately trying to escape its predators, boasts about 100 million olfactory receptors. The average cat has about 40-80 million.
A dog has up to an unbelievable 300 million of them. Scientists say their sense of smell can range up to 100,000 times as acute as ours (NOVA)!
A Jacobson’s organ is an important part of the olfactory system for many animals, and yet another reason a dog’s sense of smell is so powerful. This consists of a patch of sensory cells in the nasal cavity, allowing dogs to easily sense various chemicals, like hormone secretions.
These astonishing capabilities
In 30 minutes, one avalanche rescue dog is able to search an area spanning 10,000 square meters, compared to the 4 hours it would take a human rescue worker! By that time, an avalanche victim would probably be long dead, making these dogs irreplaceable.
A blood hound, known to be the best tracking breed in the world, can’t easily smell ‘through’ water, but he can detect the microscopic scent particles that wash along riverbeds. This means, for even the stealthiest criminal outside on foot, there would be absolutely no escape.
Military dogs have been (and are currently) trained to detect invisible, buried explosives no soldier would see, and have saved countless lives. In some cases, dogs can follow a scent trail weeks after it has been laid, even sometimes buried down to 40 feet underground!
Some dogs are even being trained to detect cancerous cells growing within a human patient!
A world seen through a nose
Unlike us humans, who have evolved to survive by using tools that we can see, a dog’s survival in the wild depends on his nose. In a way, you could say they ‘see’ the world through their noses just as acutely as we do with our sight. In today’s world, a blind pet, or an amputee with only three legs, would continue life happily like nothing is wrong at all. Taking away their sense of smell would be a devastating blow indeed.
According to the American Kennel Club, about 25% of dogs have eaten their own faeces at least once. If you’re a pet owner, you’ve probably seen your dog roll in something foul outside, to your displeasure. Why do they seem to enjoy the same things that smell so bad to us?
The simple answer is it doesn’t smell bad to a dog. Where we smell one thing we don’t like, a dog can tell what it is made of, how long it’s been there, where and what animal it came from, if the other animal is in heat or what gender it is, if it’s a predator, and probably how old it is. By simply smelling the ground (or a tree) where another dog urinated 2 days ago, a dog instantly knows everything about the other.
In fact, urinating on a standing object is known as scent marking, a way for one dog to send messages to others. This explains perfectly why your dog might want to stop to eliminate 20 or so times during your walks.
Why do dogs rolls about in bad smells?
We still don’t know exactly why dogs roll in scents on the ground. Many biologists believe it is either a way of masking their own smell, which makes perfect sense for a predatory animal, or another way of conveying messages to other dogs. Some think this ‘rolling’ is an instinct inherited from an age when wolves would carry scents back to the pack.
Why does one dog seem to have his nose glued to the but of another? Again, he is receiving messages about the other dog by smelling these areas. Is the dog in heat? Dogs can read vital information from anal secretions from two small sacs just inside their bums. According to veterinarians, no one dog has the same secretions as another, making it easy for them to tell each other apart. Dogs have more, heavily clustered secretion glands (apocrine glands, a type of modified sweat gland) centred in these areas also.
Believe it or not, a dog can easily detect an ovulating human, which is one reason why it may jab its nose in that area (to the unfortunate embarrassment of that particular lady).
In conclusion: It’s a dog’s world
Whereas we humans see a bright, colourful world with our acute eyesight, the vision of a dog is designed to detect smaller, faster movements, better in dim light. What objects we see clearly a few yards away may seem very blurry to a dog, which is one reason traffic can be such a danger. Whereas dogs do see in colour, they can’t see in the full spectrum we can and have difficulty detecting various shades.
Their nose, however, more than makes up for anything their eyes lack! Not even our advanced 21st-century human technology can match it.