Originally published May 5, 2016
My childhood Ragdoll cat, Rags used leave his mouth open after he would smell things quite frequently, and I came to hate it because it was often after smelling urine or another cat’s butt. But, when I found out what he was doing, I thought it was pretty rad.
You know what I am talking about – where they leave their mouth slightly open and then sort of daze off for a second and then lick their nose and close their mouth again?
Last week, I ran across the street to a neighbor’s house to grab their recycle bin that had been at the curb for a few days – I figured they were out of town, so I put the bin behind their house and came back home. When I came back home, Charlie would not stop smelling me and I
couldn’t figure out why until later when I had stopped by my parents house and Caymus couldn’t leave me alone either – Caymus never shows attention like that, so I knew I had something on me. Came to find out that the recycle bin had been sprayed by a male cat and I had the smell of urine on my pants – LOVELY.
So when I came home, I immediately changed out of my
pants and had Charlie and Trigg give them a good whiff, so that I could get a photo for this post!
There’s a fantastic website called, Pet Tails that lays this out more in detail and that’s where I got this information.
The act of opening the mouth and drawing up the air to the Jacobson’s organ is called the “flehmen reaction”.
Essentially, the cat is opening her mouth to suck in the air into the Jacobson’s organ and take a really deep sniff of the odor.
This special sensory organ called the vomeronasal organ or Jacobson’s organ allows a cat to have 14 times the sense of smell of a human. The Jacobson’s organ which consists of two fluid-filled sacs that connect to the cat’s nasal cavity is located on the roof of their mouth behind their teeth.
The reason they look dazed for a second or two is because they can learn a lot of information about their surroundings through their sense of smell. They mark territory using the scent glands on their cheeks and paws. The glands
secrete pheromones, which are chemical substances that stimulate a behavioral response, such as an avoidance or aggressive reaction. Pheromones are also found in saliva, feces, and urine. When cats “spray” it’s another way they are marking territory.
More About the Flehmen Response
It is a well-known fact that cats have a much keener sense of smell than us humans do, but how they manage to out-sniff us is not common knowledge.
Nor is the fact that they have more developed sensory organs than we do. One of these sensory organs is Jacobson’s organ or the vomeronasal organ, which provides them with very detailed information about a certain smell.
To use this organ, they must keep their mouths open and breathe through their mouths because its openings are located on the roof of their mouths, just behind their incisors.
As they breathe in the smell, the roof of their mouths must be wet with saliva. It is also very important they only breathe in through their mouths. In fact, this is one of the reasons why they make that odd face. They pull up their upper lip to permit as much of the smell to enter their mouths.
Scientists have described the sensory information moving through the vomeronasal organ as being something between smell and taste.
This should give you an idea of the complexity of the information provided by this organ. This suggests that cats use their Jacobson’s organ when they want to go into particular detail about a certain smell.
What is the purpose of the flehmen response?
The flehmen response is heavily tied to identifying pheromones, which is extremely important for cats. As such, it plays a huge role in interspecies communication.
The vomeronasal organ is olfactory-chemosensory organ which can help animals gather chemical messages from their peers. This is precisely why Caymus and Charlie were so interested in sniffing out the urine on the pants. They were taking in the pheromones in the male cat’s urine.
The flehmen response is much stronger in males, which have to be particularly perceptive of the pheromones of females in heat, but also to those of other males. This plays a very important role in the mating process.
This explains why in most cases, cats are using their flehmen’s response to track down smells coming from other cats. In households with more than one cat, they can be seen displaying the grimace more often.
Moreover, keep in mind that you bring in new smells in the house from outside every single day. Your cat doesn’t need to go out to sniff the smells of other cats because you are bringing them in for them.
Aside from this, cats will use their vomeronasal organs to analyze very intense smells. For instance, you may find them with their mouths open analyzing your dirty laundry, which is heavily soaked in your scent.
Where is the vomeronasal organ located?
In cats, the vomeronasal organ is located inside the roof of their mouths. It has ducts leading to the mouth and the nose called the nasopalatine canals.
On the roof of the cat’s mouth, just behind its incisors, you can see two openings. These are the openings to the nasopalatine canals, which are filled with fluid. This makes it impossible for the smell to go up passively from the mouth to the nose.
For smell to travel through the canals, it has to be soaked in saliva and pushed up until they come into contact with the organ’s sensory cells. This is where the intense mouth-breathing comes into place.
By pulling up the upper lip, the openings of the nasopalatine ducts are also more exposed and the motion propels the saliva-soaked smell up the ducts.
What is flehmen’s grimace?
This is the name for the silly face that cats make when they use their vomeronasal organ. The term flehman’s grimace refers to the moment when they pull back their upper lip, expose their teeth, and breathe into their mouths with their eyes fixed in one point. “Grimace” is used precisely to suggest the exaggerated features they display in that moment.
Flehmen Response FAQ
Do humans have the vomeronasal organ?
Yes, humans also have the vomeronasal organ. It is part of the accessory olfactory system and it is located on the anteroinferior third of the nasal septum. It has specialized olfactory cells, which function as afferent neurons (which take the information from the nose to the brain). Its function has been linked to the detection of pheromones, but there is extensive research still being conducted on this matter. Another function of the Jacobson’s organ is linked to the production of the gonadotropin-releasing hormone.
Do humans have the flehmen response?
While humans do have the vomeronasal organ, its functionality is still being researched. In fact, there is great debate about this in the scientific community . It has been discovered that even though the organ is present, humans do not display accessory olfactory bulbs that would receive the information from the vomeronasal receptor cells. This suggests that the sensory function of the Jacobson’s organ in humans is non-operative.
Are cats the only animals displaying the flehmen response?
Certainly not, there are plenty of other animals that display this response. In fact, this is a characteristic shared by mammals. If you thought that cats look adorably silly with their mouths open and their eyes popped and fixed, then wait till you get a glimpse of other animals like horses, donkeys, tigers, or even rhinos.
However, cats display some of the most developed vomeronasal organs. To give you an idea of their skills, you should know that hound dogs, which are renowned for their keen sense of smell, have 9 receptors in their Jacobson’s organ, while cats have 30 different types of receptors.
Clearing the Air About Flehmen’s Response
Is your cat disgusted with you when it has its mouth open?
It is a common misconception among cat owners that cats make the flehmen grimace – yes, it actually has a name – because they are disgusted with a certain smell. There are plenty of jokes about how cats smell their owner’s feet or shoes and then make the surprised face with their mouths open because they simply cannot stand the smell.
As you can see, that is certainly not the case. Not only are they nor disgusted, but when cats use their vomeronasal organ, it means that they are trying to get more information about a certain smell. They are essentially scanning for pheromones. If anything, it should be taken as a compliment.
So, the next time you see your kitty with its mouth open and incisors exposed, know that it is processing a very important smell. Have you caught your kitty with his or her mouth open? What were they smelling when you did? Or did you know what they were smelling? Tell us all about your flehmen response stories in the comments section below.