Understanding the Flehmen Response in Cats
The flehmen response is a fascinating and often misunderstood behavior commonly displayed by domestic cats and many other mammals. Known humorously by some as the "stinky face,” the response is entirely normal and an important part of animal communication. Contrary to misconceptions, this behavior is not related to any illness or threat to your pet’s health. Below, we explore the complexities of this action, its biological basis, and how to recognize it in cats.
What Is the Flehmen Response?
The flehmen response is a voluntary behavior that animals use to detect chemical signals in their environment. When a cat engages in this behavior, it usually opens its mouth slightly, curls back the upper lip, and appears to grimace. This allows scent molecules to reach the vomeronasal organ (VNO), or Jacobson's organ, located at the base of the nasal cavity.
Function of the Vomeronasal Organ
- Pheromone detection: Specialized in sensing chemical messages from other animals.
- Combines taste and smell: Creates a more detailed sensory profile.
- Non-volatile compound processing: Requires direct engagement with the scent source.
Cats use this mechanism primarily for intraspecies communication. It helps them assess territories, mating readiness, and even identify their own offspring.
When Do Cats Exhibit the Flehmen Response?
Your cat might display this reaction in various scenarios, particularly when encountering strong or unusual scents. Here are some common triggers:
- Urine or scent markings from other animals.
- Pheromones, especially from females in heat.
- Kittens or familiar companions in the household.
- Objects with strong smells such as shoes, bags, food, or plants.
Is the Flehmen Response a Cause for Concern?
In short, no. The flehmen response is entirely normal and healthy. It is distinct from open-mouthed breathing, labored respiration, sneezing, or panting—behaviors often associated with medical issues like
- Asthma
- Hyperthyroidism
- Upper respiratory infections
Ensuring that the behavior is indeed the flehmen response involves observing its context. It occurs briefly, usually after sniffing something specific, and the cat returns to normal shortly afterward.
Flehmen Response in Other Species
This behavior is not exclusive to cats. It is observed in a wide range of mammals including:
- Horses
- Goats
- Lions and tigers
- Sheep
- Tapirs
- Zebras
- Giraffes
- Elephants
- Bison and antelope
Interesting Facts About Flehmen
- Domestic cats have a more developed VNO than dogs.
- The response can happen with interspecies scents, like when goats react to the urine of unrelated species.
- In horses, the VNO connects to the nasal passage since they do not breathe through their mouths.
How to Support Your Cat’s Natural Behavior
As a pet owner, understanding the flehmen response can lead to better empathy and care. Here are some tips:
- Don’t interrupt the behavior if observed; it’s a healthy sensory process.
- Keep the environment clean but allow natural scent marking areas.
- Monitor for signs of illness to differentiate normal behavior from medical symptoms.
Conclusion
The flehmen response is not a cause for alarm. Instead, it’s an important behavioral tool that cats and many other mammals use to engage with their environments. Far from being the “silent killer of cats,” this expression is a vital part of their natural communication and sensory world. Recognizing and respecting this behavior can enhance our understanding and relationship with our feline companions.





