Have you ever noticed your cat pulling a face as if they smelled the most disgusting thing ever? The eyes are closed, the mouth is open, the lips are pursed, the neck is stretched—this is an expression that definitely resembles rejection. This is actually a natural reflex known as the replied Flehmen (sometimes referred to as the Flehmen grinned o reaction too). And, interestingly, it has nothing to do with detecting foul odors.
Rather, it is a technique that cats (and some other species) have evolved to process certain pheromones. So, what is it, and why do cats do it? First, we need to understand the aforementioned pheromones.
Cat Communication and the Role of Pheromones
Pheromones are messenger molecules that cats use to communicate with each other. These are chemical substances that are excreted from the body in fluids such as urine and sweat. Essentially, pheromones are a hidden form of communication. Some species use them as signals from one individual to another.
Examples of ways to use cat pheromones include:
- Rubbing their cheeks on things
- Peeing on objects and surfaces to “mark their territory”
- Emptying their anal glands when they are stressed or scared (these are two scent glands on either side of the anus)
- Slap someone on the head, identifying him as “safe”
How Does Flehmen Respond to Cats?
The replied Flehmen is a normal behavioral response that cats “perform” when they detect certain pheromones. In everyday life, cats are constantly responding to stimuli; these stimuli can be smells, pheromones, sounds, tastes, and more. By using the Flehmen’s response, cats are able to process odors and pheromones, and then access the information it may be telling them.
The point of Flehmen’s response is to bring the air holding the scent or smell to something called the vomeronasal organ (also called Jacobson’s organ). When cats perform the Flehmen’s response, two small ducts behind the incisor teeth of the upper jaw open. The opening of these ducts allows the scent or pheromone to travel to the vomeronasal organ.
This organ is a tiny little bump in the roof of the mouth that processes pheromones and hormones—not only from other cats, but also from potential predators and prey species. It sees perfume as something more than a scent, but less than a vibration.
From here, signals travel to the olfactory center of the brain, and then to the hypothalamus. This is a very important and busy part of the brain that can influence reproductive hormones and behavior.
We split the pathway into several steps, but in real time the entire process happens in seconds, or less. Your cat can decide what to do with the information obtained. They can run or they can do nothing; they can urinate or sleep; or they can look for a potential partner.
What Does Flehmen’s Response Look Like?
If you’ve never caught your cat actually performing a Flehmen’s response, you’re probably wondering what this striking and unique facial pull actually looks like.
Your cat will assume a facial expression as if they smelled something unpleasant. Their mouths are usually open and their upper lips are pursed. This exposes the upper front teeth, known as incisors. As they do all this, cats inhale to send the scent to that vomeronasal organ in their mouth.
In some cases, cats will stretch their neck or hold their head at a funny angle to optimize the processing of scents and smells. Your cat will only hold this pose for a minute or less, before resuming their normal expression and activities. If the messages are not very clear, they can practice Flehmen’s response a second or third time.
What Causes Flehmen’s Reactions in Cats?
It seems logical that the Flehmen’s response is an involuntary or instinctual action, but cats really have to decide to do this. The Flehmen response is a voluntary action that cats take when they are exposed to an interesting odor or pheromone of another animal (usually another cat).
The Flehmen’s response is commonly used by male cats smelling a female cat’s urine to determine if she is ready to mate. However, any cat can use it when they encounter a scent that they feel is worthy of further investigation.
Should I Worry About Flehmen’s Response?
No—Flehmen’s response is perfectly normal cat behavior. Despite its strange appearance, there is nothing to worry about, and your cat will not be in any discomfort or pain. Your cat will usually be completely calm.
Flehmen’s response should be distinguished from cats that breathe with their mouths open for long periods of time. These cats are usually in distress and have difficulty or rapid breathing. Open mouth breathing is definitely concerning and requires a visit to the vet.
Conclusion
Many other animals show the Flehmen response, including horses, giraffes, lions, tigers, and more. Some people may have vomeronasal organs, but they don’t work in humans; in other words, they are a remnant of evolution that we don’t use.
We hope this article helped you understand this strange behavior from your cat!
Featured Image Credit: Bea Llonador, Shutterstock
