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I Am Your Dog's Vomeronasal Organ

Just in case you didn't know, dogs have a special olfactory sense organ that plays a major role in their lives. Also known as the Jacobson's organ, the vomeronasal organ lives quite in the shadow, secluded as it is up by the dog's nose. Indeed, it wasn't until 1732 that Frederik Ruysh discovered it, and then later in 1813, it was rediscovered by Ludwig Jacobson, hence this organ's name. Interested about the role of this organ? Let's see what the dog's vomeronasal organ has to say!

Introducing the Dog's Vomeronasal Organ


Hello, it's your dog's vomeronasal organ (VNO) talking! Yes, the introduction has it right. I am not very popular, indeed, many dog owners aren't even aware of me. But let me tell you something, I am one important piece. Sure, I may not seem to be as important as other life-sustaining organs, but I do cover some important functions.

Where am I located exactly? I am a long pouch-like structure located close to your dog's vomer and the nasal bones (hence my name), right by the inferior part of your dog's nasal septum and in the anterior portion of the palate.

You never see me, but you can sure see me at work, when your dog is busy analyzing smells. Unlike the mucosa in your dog's nose, I am lined with microvilli instead of cilia.

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I Convey Messages

What is my main job? I am responsible for conveying chemical messages known as pheromones which are purposely left behind by other dogs for reproductive or other social purposes.

horse flehem response

I am lined up with olfactory receptor cells responsible for detecting these chemical messages which are then relayed to the dog's amygdala and hypothalamus, important parts of the dog's brain that generate emotional and behavioral responses.

To receive these chemical messages, since they're non-volatile, it's necessary that they make contact with me. Have you ever seen horses who lifted their lips exposing their front teeth as if they were laughing? This is known as a "flehem response" and what the horse is really doing is he's helping those pheromones or other scents reach me.

Other animals exhibit similar behaviors such as snakes flicking out their tongues, cats opening their mouths and wrinkling their noses in a grimace, and elephants using the tip of their trunks.

You won't likely see though your dog exhibit a flashy flehem response as seen in horses, but dogs actually do something similar when they're smelling something such as urine. They might push their tongue against the roof of their mouth, (tonguing) so to send some pheromones to me through special ducts found right behind the top front teeth (the incisive papilla) which connect the mouth with me.

You may also notice some dogs foaming at the mouth and teeth chattering as they do this. Pssstt.. wanna see an image of an incisive papilla in a dog? Then click here and here.

A Natural Communication System

dog nose detects cancer

As mentioned, I specialize in relaying information deriving from non-volatile compounds and most of them are pheromones. What are pheromones exactly?

According to Karlson and Luscher (1959) they are “substances secreted to the outside of an individual and received by a second individual of the same species in which they release a specific reaction..."

Where do they come from? Pheromones secreting glands are found in the dog's ears, lips, genital/anal area, between the toes and by the inter-mammary sulcus, explains Bonnie Beaver, Diplomate of the American College of Veterinary Behaviorists in the book "Canine Behavior: Insights and Answers."

While it may seem like your dog's life doesn't depend on me as much as with other life-sustaining organs such as the heart, liver or kidneys, I play an important role in reproduction and survival by generating appropriate behavioral responses. You must thank me if dogs are able to coordinate their activities with other dogs without saying a word. What type of messages do I pick up and transmit to the brain? Here are a few examples.

Reproductive Pheromones

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Intact male dogs rely on me to determine the reproductive status of female dogs. When male dogs are exposed to female urine, the pheromone content can help determine if she's receptive. The compound has been identified as methyl p-hydroxybenzoate, and according to a study, when this compound was applied to spayed female dogs, it caused male dogs to attempt to mount.

Alarm Pheromones

Alarm pheromones may be left behind by frightened dogs. There's belief that when dogs spontaneously empty their anal glands during fear, alarm pheromones may be secreted, explains Sarah Heath, a European VeterinarySpecialist in Behavioural Medicine. Dogs in waiting rooms at the vet may pick up these pheromones and react in a stressful manner.

Territory/Information Pheromones

dog marking

Why do dogs scratch the ground after they eliminated? They release pheromones from their paw pads which are detected by other dogs and may signal territory.

Pheromones are also left behind in dog pee, which explains why dogs are so obsessed in marking and sniffing it. These pheromones tell a whole lot about other dogs! Dogs may react differently to pee, some just sniff it and leave the area, while some others will pee on top of it.

Did you know? Some puppy potty training pads or pee posts are sometimes treated with synthetic pheromones for the purpose of grabbing the pup's attention and hopefully enticing him to soil on them next time nature calls. Whether they work on not though remains a subject of controversy.

Calming Pheromones

Some pheromones make dogs alarmed, while others calm them down. When mother dog gives birth, she releases special pheromones which are meant to comfort her puppies. Today, a synthetic form of dog appeasing pheromones (DAP) is made to craft special dog appeasing pheromone plug-ins and collars. These DAP products have been found to calm down anxious dogs even if adult.

As seen, I do a whole lot! So next time your dog is sniffing, think about me, and how fascinating it is that I relay information left from other dogs even after they're gone! I hope this has helped you understand my important roles better, have a good rest of your week and send some lovely pats to your dog.


Your Dog's Vomeronasal Organ

Dog Pawprint


  • Karlson P., Lüscher M. Pheromones: A new term for a class of biologically active substances.Nature. 1959;183:55–56.
  • Veterinary Nursing Journal, Volume 22, Issue 9, 2007, Understanding pheromones, by Sarah Heath
  • Wikipedia, Vomeronasal Organ, retrieved from the Web on March 14th, 2016
  • Wikipedia, Flehem Response, retrieved from the Web on March 14th, 2016

Photo credits:

Flehmen response in a horse by Brandinian - Own work, sjp horse, public domain

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