Why Cats Make Weird Faces After Smelling: The Flehmen Response Explained
Pet owners often notice their cats pulling unusual facial expressions after sniffing certain objects—mouth slightly open, upper lip curled, and a look of pure concentration. This isn’t your cat being dramatic; it's displaying what scientists call the flehmen response, an important behavior for chemical communication among mammals.
What Is the Flehmen Response?
The flehmen response is a voluntary reaction in which an animal curls back its upper lip, exposing its teeth and inhales deeply, often through a closed nose. This behavior helps direct scents—especially pheromones—to the vomeronasal organ (VNO), also known as Jacobson’s organ, located at the base of the nasal cavity.
How It Works
- Mouth opens slightly, upper lip curls back
- Scent particles are taken in
- These particles are transferred via ducts to the vomeronasal organ
- The VNO processes the chemical signals, generating a sensation that is a blend of taste and smell
This sensory system primarily detects non-volatile organic compounds such as pheromones present in urine or secretions. It allows the cat to gather important social and sexual information from its environment.
Common Triggers in Cats
Cats exhibit the flehmen response when encountering substances that may hold chemical messages. These include:
- Urine or scent markings from other cats
- Female pheromones, especially when a male detects a female in heat
- Litter boxes and other scent-concentrated areas
- New objects or strong smells like catnip, food, shoes, or plants
- Kittens' scent, especially for mother cats tracking their young
What Does the Flehmen Face Look Like?
The expression that comes with the flehmen response may appear odd or humorous. Common characteristics include:
- Partially open mouth
- Curling of the upper lip
- Exposed front teeth
- Wide or squinting eyes
- A lifted head or stretched neck
This posture helps the cat efficiently pull scent particles into the mouth and up to the vomeronasal organ. The entire behavior usually lasts just a few seconds but can be very intense.
Why Cats Use the Flehmen Response
The flehmen response plays a crucial role in intra-species communication. It enables cats to gather information about:
- Territorial claims
- Sexual receptivity in potential mates
- Individual identification among cats
- Reproductive synchrony in social groups
Male cats, for instance, use this response often to determine if a female cat is ready to mate based on the chemical makeup of her urine.
Flehmen Across the Animal Kingdom
The flehmen response isn’t unique to domestic cats. It’s observed in many other mammals including:
- Horses
- Goats
- Tigers & Lions
- Sheep
- Tapirs
- Elephants
- Giraffes
- Zebras
- Antelope & Bison
- Rhinoceroses
Even some animals like hedgehogs and dogs possess vomeronasal organs, though cats are believed to have a more refined response due to the diversity of receptor types in their VNOs.
Is Flehmen the Same as Open-Mouth Breathing?
No. The flehmen response is not a symptom of illness. It differs significantly from behaviors associated with distress, such as:
- Panting
- Sneezing
- Yawning
- Teeth chattering
- Labored breathing (e.g., asthma, hyperthyroidism)
The flehmen response is brief, normal, and healthy and indicative of your cat’s instinctual need to interpret its environment through scent.
Inter-Species Flehmen Response
Interesting studies have shown that in some cases, inter-species flehmen can occur. For example, goats may respond to the urine of other species, suggesting that some chemical markers transcend specific animal types and can trigger similar reactions across species.
Conclusion
The next time you catch your cat making a “weird face” after sniffing your shoes or a new piece of furniture, know that it’s just engaging in the evolutionary behavior of the flehmen response. This powerful sensory mechanism helps your feline friend read the chemical messages that shape its world—from understanding territory and social dynamics to determining reproductive status and more. Whether it’s investigating a freshly marked litter box or learning about another animal in the household, your cat’s strange flehmen face is actually a sophisticated process of environmental decoding at work.
