Your dogs nose (and why you should let them sniff)

Your dogs nose is amazing. Fact. But how do we know it is amazing? How does it work? How good are humans at following scent trails compared to dogs? Read on for all of these answers and more.

A scents journey from air to brain

We know dogs can smell all sorts of different scents in great depth, and are far more sensitive to smell than we can comprehend. Our noses pale in comparison. But why? 

Well, in the dogs brain, the olfactory centre that is responsible for controlling all things smell is three times larger than in human brains. That means that even though a dogs brain is smaller than a humans, the part in charge of smell is way bigger. This size difference means they can pack tonnes more neurons and pathways in there; fitting in lots of equipment for understanding, processing and responding to scent.

The nose

How scent gets to the brain is a fundamental part of olfaction. You can't smell anything if the scent doesn't travel in your nose in the first place! Dogs noses are wet to allow scent to stick to it, and to provide liquid so that when the air moves inside it becomes warm and humid like a vapour. This makes it easier for scent to travel into the nasal passage and for scent to be detected. 

In order to smell stuff, dogs have a unique way of inhaling, or sniffing. They can inhale and exhale rapidly, due to the structure of the nose itself. Either side of your dogs nose, there are two slits; these spiral out from under the nostril. Air will be inhaled through the nostril itself and is exhaled through these slits during bouts of sniffing, allowing the exhaled air to kick up some of the scent from the ground but lessening the impact of disturbing and further diluting the scent underneath the nostril itself. This is how your dog can sniff so rapidly. The next time your dog is sniffing the air or looking as though they're simply looking around them, watch their nose, and see if you can see it moving as they smell the breeze.

The vomeronasal organ (or how dogs smell with their mouth)

Inside your dogs mouth, just behind their front teeth, is a small segment of tissue that is called the vomeronasal, or Jacobson's, organ. Chemical compounds that arrive into the dogs mouth in liquid form can be detected with this organ, and the 'scent' of these transferred to the vomeronasal bulb in the brain. Whilst these liquid 'smells' are not processed by the olfactory bulb, the vomeronasal organ is still considered part of the olfactory system as it helps dogs detect pheromones and other information from the environment. Some dogs will even taste the urine or faeces of other dogs in order to gather more information through the vomeronasal organ. Humans have vestigal versions of this organ at the roof of our mouth about a centimetre behind our front teeth. You can feel where it should be with your tongue!

Nasal cavity cells and tissue

Once inside the nose and nasal cavity, each cell has little legs called cilia. Cilia are present in lots of cells, but the ones in the nose have tonnes of scent receptors that can receive the scent chemicals and send that information all the way up to the olfactory bulb in the brain. The surface area inside the dogs nasal cavity is huge, much greater than a humans, helping to translate all of those scent molecules into readable messages to send to the dogs brain. Whilst we may have less than 10 million scent receptors helping us decode smells, dogs have hundreds of millions, so can understand and interpret scent in ways we simply cannot comprehend!

Tracking, trailing and scent plumes

A study carried out in 2007 (Porter et al) found that humans could learn to track scent, but whilst they got a bit better with practice, their noses still were not as sensitive as the dogs. However an interesting note stood out from this study, one that highlighted a certain behaviour that dogs do that was seen in the human test subjects. Often when trainers get calls about dogs that pull on lead, weaving side to side across the footpath is a big part of that. "Oh he pulls left to right, right to left, he's all over the place!" However, when mapped out, how animals follow scent tends to be in a weaving pattern. When scent is dragged in a straight line across land for tracking purposes, the scent from the line will travel with the breeze, or gather like smoke rising from a flame. These scent plumes can veer left or right in the air, and the individual who is sniffing them out will follow each plume, losing them then veering back to try and 'catch wind' of it again. This leads to what we see as a zig-zagging motion. The next time your dog veers off course to go and smell something, take a second to appreciate their nose, and what must be an incredibly interesting scent to suddenly change direction for. 

If you would like more information on scent, airflows, competitive/detection dog work or another aspect of scent that we didn't cover here, let us know and we can create another post going into more depth! Follow along on Facebook, Instagram or on our website for more information and for training or dog walking services.