Understanding the Flehmen Response in Cats
Cats have a range of fascinating behaviors, and one of the most intriguing is the
flehmen response, often humorously referred to as the "stinky face". This peculiar expression is a purposeful action that helps felines analyze complex scent molecules in their environment. Despite how odd it may appear, the flehmen response serves important functions in a cat’s social and reproductive communication.
What Is the Flehmen Response?
The flehmen response is a
voluntary behavior displayed by many mammals, including domestic cats, lions, tigers, horses, and goats. It involves the animal
curling back its upper lip, holding the mouth slightly open, and exposing the front teeth. This creates a distinctive grimace that is typically held for just a few seconds.
The Function of the Flehmen Response
The main purpose of this response is to assist in detecting
chemical signals, primarily
pheromones and hormones, secreted by other animals. These signals are processed by a specialized sensory structure known as the
vomeronasal organ (VNO) or
Jacobson’s organ, located at the base of the nasal cavity. When a cat exhibits flehmen, its posture and mouth position allow air and scent molecules to travel directly to the VNO.
How the Vomeronasal Organ Works
Most mammals with a flehmen response have an opening on the roof of the mouth behind the upper front teeth. This opening connects to
ducts that lead scents to the VNO, where the animal experiences the odor as a combination of
taste and smell. The VNO specially processes
non-volatile organic compounds, which usually require direct contact with the source of the smell.
Common Triggers of the Flehmen Response in Cats
Cats are particularly responsive to potent scents. The following stimuli commonly trigger the flehmen response:
- Urine or scent markings left by other cats or animals
- Female pheromones, especially during heat cycles
- Mother cats locating their kittens
- New or intense smells such as catnip, food, or plants
- Foreign household odors like shoes or bags from outdoors
Cats display this behavior most often in areas with a high concentration of smells, such as litter boxes, toys, doorways, or sprayed objects. The purpose is consistent: to
gather information about who or what has been there and what that scent communicates.
Behavioral Description
When a cat displays the flehmen response, its body language includes:
- Mouth slightly open
- Upper lip curled back
- Front teeth exposed
- Brief squinting or wide eyes
- Neck extended with nose close to scent source
This expression should not be mistaken for other behaviors like panting, sneezing, yawning, or signs of respiratory distress. Unlike involuntary symptoms, flehmen is a
deliberate and short-lived action following a sniff.
Biological Importance
The flehmen response plays a key role in
intra-species communication. In particular, it helps:
- Identify reproductive status in others
- Synchronize mating readiness among animals
- Promote social interactions between group members
Male cats, for example, frequently use this response to detect if a nearby female is in heat by smelling her urine. However, any cat—male or female, sexually active or not—can exhibit the flehmen behavior upon encountering an unusual or significant scent.
Flehmen in Other Animals
Flehmen is not unique to cats. Other mammals that express similar behavior include:
- Lions
- Tigers
- Goats
- Sheep
- Giraffes
- Elephants
- Horses
- Bison and zebras
Dogs also possess a vomeronasal organ, yet cats are believed to have a
more pronounced and sophisticated flehmen response due to a greater number of receptors in their VNO.
Inter-Species Flehmen
Interestingly, there are cases of
inter-species flehmen responses, suggesting that some chemical signals—especially those in urine and reproductive secretions—contain universal elements that elicit responses beyond species boundaries.
When to Be Concerned
While the flehmen response is normal, pet owners should distinguish it from symptoms of illness. If a cat is panting heavily, showing labored breathing, or persistently keeping its mouth open without stimulus, it may be experiencing a medical issue such as
asthma or hyperthyroidism. In those cases, veterinary attention is essential.
Conclusion
The flehmen response is a remarkable, intentional behavior that cats use to process crucial social and reproductive information through scent. Triggered by specific smells—particularly pheromones—this response enables cats to interact more effectively with their environment and with other animals. Observing your cat make this 'stinky face' is not only normal but reflects an advanced chemical communication system shared by many mammals.
