It comes as no surprise that dogs have a really good sense of smell. What perhaps IS more surprising is just how much better it is than ours.
Back in 2002, scientists from the Sensory Research Institute at Florida State University designed and carried out a study to try to put a dog’s sense of smell into context. For this, they used a substance called n-amyl acetate—an organic compound with a scent similar to apples and bananas. It is commonly found in penicillin, as a paint solvent, or as a flavouring.
The study, documented by Dr James Walker, discovered that a dog can detect such tiny amounts of this substance they are hardly measurable—two parts per trillion, to be precise. That means a dog’s sense of smell can identify chemicals between ten-thousandth and one-hundred-thousandth more diluted than a human is capable of.
So, while a human might be able to tell from a sniff if a cup of coffee has a teaspoonful of sugar added to it, a dog would be able to tell if that teaspoonful of sugar had been added to a million gallons of water.
Or, if you relate this to vision, something a human could see clearly at a third of a mile, a dog would be able to see, just as clearly, at 3000 miles away.
Mind-boggling, isn’t it?
I recall reading, years ago, about cadaver dogs that would indicate for a corpse submerged in nearly a hundred feet of water. Since then, I have heard of drug-detection dogs who can find marijuana in sealed containers immersed in a vehicle fuel tank, or those who smell whale scat from a mile away across a sea inlet. Not to mention all those dogs who sniff out explosives.
More recently, I met two dogs working for my local authority. One of them had been trained to indicate hidden money. When he insisted that a fireplace in one property was a hotspot (pun intended) and it was knocked down, they found £20,000 in cash had been bricked in behind it. The occupants of the house claimed it must be a gift from Santa Claus…
The other dog was trained to help investigate arson by sniffing out when accelerants had been used. A study carried out in 2003 discovered that when tracker dogs meet a human trail at right-angles, they can distinguish the direction in which the person was travelling within five paces. And this is despite all the other scents and smells that have come along since the target passed that way.
All kinds of breeds are used as detection dogs. One of the reasons bloodhounds are favoured a trackers is apparently because those long floppy ears help to waft the odours into its nostrils as it moves, nose downward, along the ground. Dogs can also independently move each nostril, to further help divine the direction of the scent they’re following.
Not only do dogs have approximately 300 million olfactory receptors in their noses, compared to around six million for a human, but the area of their brains devoted to analysing those odours is forty times greater than ours, proportionally speaking.
And even the shape of a dog’s nostrils is designed to aid its sense of smell. The ‘comma’ shape allows a dog to exhale through the side slits, which creates a swirling air pattern that helps sweep more of the scent in via the front of the nose. A study carried out in Norway by the University of Oslo discovered that a hunting dog can sniff in a stream of air for up to forty seconds at the time, which covered about thirty actual breaths.
As if all this wasn’t enough, dogs have a secondary olfactory system that humans don’t possess. The vomeronasal or Jacobson’s organ, which is at the base of a dog’s nasal passage, picks up pheromones, related to sexual readiness. These signals are interpreted by a different area of the dog’s brain, quite separate from the rest of its scenting capabilities.
You may wonder what sparked this post today about the ability of dogs to detect chemicals by scent alone. The answer lies all around us at the moment—the Covid-19 pandemic. With testing apparently in disarray, the scares about asymptomatic carriers and threats of a second wave, could scent dogs provide part of the answer?
It was reported back in July 2020 that a charity in Milton Keynes, UK, called Medical Detection Dogs was training six canines to sniff out the virus. The charity’s co-founder, Dr Claire Guest, has previously trained dogs to detect various forms of cancer, as well as malaria, E.coli, and Parkinson’s disease. With the increasing scepticism towards vaccines, using the biosensors known to man might just provide a worthwhile alternative.
MDD is continuing its trials, part-funded by the UK government and by public donations, in conjunction with the London School of Hygiene & Tropical Medicine and Durham University. It is hoped they might be able to screen up to 250 people an hour at points of entry into the UK and at testing centres.
This week’s Word of the Week is nefelibata, meaning a cloud walker, one who lives in the clouds of their own imaginations or dreams, or one who does not obey the conventions of society, of Spanish and Portuguese origin.
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