Why Do Dogs Have Slits on Each Side of Their Nose?

August 28, 2014

dog nose kathleenBy Linda Cole

My dogs know before I put them outside if there is an animal near their dog pen, even in the winter with the windows down. By the time they get outside, they’ve already pinpointed the area where a cat, possum or other small animal is. A dog’s nose is amazing. Everything about a dog’s nose is designed to give him a sort of “super power” when it comes to smelling. Even the slits on each side of their nose have a specific function.

Every time a dog breathes, he pulls in smells. The canine sense of smell is 10,000 to 100,000 times better than ours. James Walker, former director of the Florida State University Sensory Research Institute, came up with a good visual to explain the difference between our sense of smell compared to a dog. “If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well,” he said.

Another way to grasp the power of a dog’s nose is to imagine two million barrels of apples sitting in a warehouse. A dog could walk in and detect the one rotten apple hiding among all the others. Once a dog has been trained to detect a specific scent, such as drugs, bedbugs, cancer or low blood sugar, he can find it regardless of other scents around him. One reason why canines can isolate a scent is due to the slits on each side of their nose.

Compared to our ability to distinguish between 4,000-10,000 different smells, dogs can process 30,000-100,000 scents. Because they use scent more than the other senses to navigate through their world, the amount of brain power devoted to their sense of smell is 40 times greater than ours. As a dog inhales, the air is separated and splits into two different paths. One path takes about 12% of air to the back of the nose for scent analysis, and the rest passes through that area and goes to the lungs.

dog nose marcoThe air that stays at the back of the nose is filtered through a maze of ruffle-like bony structures called turbinates that sift out odor molecules according to their chemical makeup. Olfactory receptors in the tissue of the turbinates then recognize an odor based on their shape, and send impulses to the brain to process.

The slits on each side of the nose give dogs the ability to have a constant stream of air that can span many respiratory cycles. When we inhale and exhale, the air goes out the same way it came in and any odors that entered are forced out along with the air. In dogs, exhaled air goes out through the slits and the swirling motion of air helps new odors enter the nose. This makes it possible for a dog searching for smells to have a steady stream of air coming in for up to 40 seconds, and maybe even longer.

The slits also allow dogs to wiggle each nostril independently, and give them the ability to know which nostril a smell entered. This is how a dog can pinpoint where a smell is coming from, and why a canine searching for smells on the ground will weave back and forth as he follows a trail.

At the bottom of the canine throat is a second structure found in cats and other mammals: the Jacobson’s organ, which is used to pick up pheromones. The smells it detects are sent to a part of the brain that’s devoted to only analyzing the pheromone molecules it picks up. It lets dogs smell and taste the scent. If you’ve ever seen your dog sniffing with his mouth open in a sort of grin, he’s having a Flehman Reaction and catching a whiff of a female in heat or sniffing urine left by another dog.

dog nose ann-dabneyOnce a dog has learned a scent, he can remember it for a long time. Certain dog breeds like the Bloodhound and Basset Hound have some added features that increase their scenting ability. Their long ears help sweep up smells from the ground, and loose skin around the chin traps scents.

The slits in a dog’s nose enhance their sniffing ability so they can follow prey, locate someone lost in the woods or buried under snow, and root out their CANIDAE treats no matter where you hide them. When you see your dog with his wiggling nose in the wind, you can bet he’s savoring every bit of information that’s riding in the breeze. That’s a pretty remarkable feat when you think about it!

Top photo by Kathleen Tyler Conklin
Middle photo by Marco
Bottom photo by ann-dabney

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Comments

  1. Mom Kim here – That’s interesting. I always wondered how Shiloh and Diva Shasta (my 2 Beagles) could stand at the closed back door, gazing/barking excitedly out the window and then when I opened that door, they would make a beeline for the far back fence – tails wagging excitedly the whole time while barking and aroo-ing the whole time. After they made sure any critter was gone, then they would start sniffing and excitedly wimpering in the yard all around where the critter was. I have no idea how many times they have done this – and I never tire of listening and watching them do it 🙂

  2. DMatsuura says:

    I never knew why dogs have slits on the side of their nose. Wonderfully informative article.