Why Do Cats Open Their Mouth When They Smell? (Explained!)
If you share your life with a cat, you’ve probably noticed that she often opens her mouth when she’s having a good old smell of something.
It looks a bit like a grimace and can last several seconds. But have you ever wondered why your feline friend makes this funny facial expression?
Is it just another quirk of her feline nature, or is there a scientific reason behind it? Read on and all will be revealed!
A cat’s sense of smell
A cat’s sense of smell is one of her primary methods of communication. Indeed, cats have a keen sense of smell and are “probably capable of distinguishing among many thousands of different smells,” says cat behavior expert John Bradshaw.
Cats use their sense of smell for all sorts of things, from finding mates to identifying other cats, from locating food to figuring out if an area is safe, from establishing their territory to a navigation aid.
The membrane in a cat’s nose that helps her smell things (aka the olfactory mucosa) is, at an estimated 20-40cm sq (approx 3.1-6.2 sq. inches), about twice the size of that of humans.
Quite astonishing for an animal that is so much smaller than we are!
Feline scent glands
Cats have scent glands on several areas of the body, including the forehead, chin, cheeks, lips, paws, tail, and side of the body.
When they rub on things, people, or other cats, they deposit their scent and leave their mark
And when a cat rubs her face against something, she’s not just trying to make it smell like her. She’s also spreading cat pheromones from those scent glands. These are chemical substances that convey all sorts of information to other cats.
It’s the same for humans – when your cat rubs her head against you (or a doorframe or an item of furniture), she’s actually depositing pheromones.
This is known as “bunting” and it’s the cat’s way of “depositing scent as a bonding gesture.” (Johnson-Bennett, 2022).
Why is my cat making a funny face?
I’m sure you’ve seen your cat come across an interesting smell and give it a real good sniff, before making a strange face with an open mouth, as if she’s just smelled something unpleasant.
She’ll sort of wrinkle her nose and pull her upper lip back into what is almost a look of disgust.
She’ll usually stay that way for several seconds too.
You may have seen it when your kitty is smelling something new, like something you’ve just brought home from the shops.
You might also see her do it when she picks up on the pheromones of another cat or even when she smells her human!
(This is probably TMI but I often see our cats do this if they happen to sniff shoes after I’ve been to the store or my armpit after a long bike ride. Their choice, not mine.)
Anyhoo, what your cat is doing here is inhaling through her nose while holding her mouth open at the same time.
You can see an example of what I’m talking about in this video:
The science bit
Cats have “two small air passages known as the nasopalatine ducts, which are located in the roof of the mouth just behind the upper front teeth (incisors),” explain Dr. Marty Becker and colleagues.
“Air in the mouth passes through the ducts, which lead to the vomeronasal, or Jacobson’s, organ in the nasal cavity.”
The vomeronasal organ is like an extra olfactory organ. It gives your cat a much better sense of what she’s smelling, almost as if she can taste it.
In fact, scientists believe the information processed by the vomeronasal organ “lies somewhere in between the sense of smell and taste.” (Bittel, 2016).
What is the vomeronasal organ?
The vomeronasal organ is a specialized organ, a collection of sensory cells within the main nasal chamber that detects heavy moisture-borne odor particles.
In contrast, airborne odors, are detected by the olfactory sensory cells located in the main nasal chambers. (Encyclopedia Britannica).
That’s pretty interesting stuff.
What is the flehmen response?
The scientific name for the funny face animals make when engaging in this weird sort of grimacing/sniffing behavior is the flehmen response.
It’s not exclusive to cats either.
You’ll see other animals, such as dogs, goats, hedgehogs, elephants, giraffes, and of course, big cats, do it too. Although it’s easiest to spot in domestic cats and horses (Wikipedia).
What is the purpose of the flehmen response?
The flehmen response allows animals to analyze pheromones in greater detail.
By curling back their lips and wrinkling their nose, they can channel the pheromones into the vomeronasal organ for further analysis.
It’s a different process than simply breathing in through the nose and smelling a scent. The flehmen response “is a voluntary action, like swallowing,” says Jason Bittel.
What scents trigger the flehmen reaction?
In cats, we most often see the flehmen response in relation to the urine and feces of other cats, which typically contain information about other cats.
Reproduction
The flehmen response is usually triggered by strong scents, particularly those related to reproduction.
For example, male cats may use the flehmen response with pheromone detection in a female’s urine, which can help them determine if there’s a mating opportunity.
Similarly, female cats may use the flehmen response to assess the quality of a male’s genes. And a cat in heat will often show the flehmen reaction when she smells a tomcat’s (i.e. an unneutered male cat) urine.
Territory
Additionally, the flehmen response can also be seen when cats encounter areas that have been marked with another cat’s pheromones.
In these cases, the flehmen response can help cats to gather information about other members of their social group.
Aggression
Evidence also suggests that Jacobson’s organ “may be involved in the detection of chemical signals related to aggression.” (Encyclopedia Britannica).
Overall, the flehmen response is an important part of a cat’s sense of smell, and it plays a crucial role in their social behavior.
Do male cats engage in the flehmen response more than female cats?
According to Dr. Becker and colleagues, the flehmen response is seen “primarily in male cats” specifically in its role to better assess the reproductive readiness of females
Females (i.e. mother cats), on the other hand, are “more likely to display the flehmen response when sniffing their newborn kittens.”
And any cat “may flehmen in response to the scent of catnip, the urine of other cats or to any unfamiliar smell.”
Why is it called the flehmen response?
According to Wikipedia, the name comes from the German word “flehmen,” which means to bare the upper teeth.
It’s also sometimes known as the flehmen position, flehmen reaction, flehmen grimace, flehming, or flehmening.
Why is it called the vomeronasal organ?
The vomeronasal organ is named because of its proximity to the vomer and nasal bones.
Why is it also called Jacobson’s organ?
This vomeronasal organ is also known as Jacobson’s organ, named after its discoverer, Danish anatomist Ludvig Levin Jacobson, in 1811 (Encyclopedia Britannica).
What is blepping?
“Blepping” occurs when your cat leaves her tongue sticking out for no apparent reason. It can happen after grooming, eating, licking, meowing, or just about any other activity.
The jury is still out on exactly what blepping means, but some believe it could be another way for cats to investigate an interesting scent or process sensory information. Or maybe it’s simply a sign they’re feeling relaxed.
According to Dr. Hannah Godfrey, if your cat’s not a regular blepper and you suddenly notice the behavior, it could be a sign that your furry friend is feeling sick or has a sore mouth, or even is struggling to breathe.
In such cases, please consult with your veterinarian as soon as possible to examine possible medical conditions or health problems.
Final thoughts
Understanding how our cats use their powerful sense of smell can help us cat owners gain a better insight into how they’re feeling, and appreciate all the ways they communicate with us and the world around them.
So next time you see your cat sniffing something intensely and grimacing strangely, don’t interrupt – she’s just trying to figure out what that particular thing smells like!
READ NEXT
Resources
- Cat Scents – Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker
- Cat Sense – John Bradshaw
- Flehmen response – Wikipedia
- How Cats Use Scent Communication – Pam Johnson-Bennett
- Jacobson’s organ – George R. Zug
- Why Do Cats “Blep”? A Veterinarian Explains – Dr. Hannah Godfrey MRCVS
- Why Do Dogs, Cats, Camels, and Llamas Make That Weird Face? – Jason Bittel
