The Flehmen response in dogs and many other mammals is a natural reaction to a new or strange smell. ย Urine is one of the most common causes of the Flehmen response in dogs, but some male dogs may show the Flehmen response when they smell a female dog nearby. The male dog may also show teeth chattering after sensing the femaleโs presence.
Classic signs of the Flehmen response are:
- Curled-back and raised upper lip, often with wrinkles near the nostrils
- Raised head
- Exposed teeth, possibly with chattering
- Open mouth
However, you may not always notice the Flehmen response in a dog.
Horses are widely believed to have the obvious Flehmen response with a marked raised upper lip, wrinkled nostrils, and a raised head. In dogs, says a study published in 2022 in Animals, itโs not as easy to identify: ย โThe typical Flehmen reflex is not observed in dogs and cats because their upper lips are too rigid and firmly fixed via the frenulum to permit this type of movement. These animal species exhibit different attitudes of behavior, namely they assume a position with an upright head and neck, which they stretch forward for a short time.โย In dogs, say the researchers, there often is a rapid retraction of the tongue that likely aids in the perception of pheromones.
This doesnโt mean dogs donโt do the Flehmen response (they do, read on). It just means it isnโt always obvious to an onlooker.
Jacobsonโs Organ in Dogs
The open-mouth part of the Flehmen response allows Jacobsonโs organ to be maximally involved. Jacobsonโs organ, also known as the vomeronasal organ, consists of sensory cells in the front of the nasal cavity, just behind the incisors (the little teeth in front between the long canines, or fangs). Danish physician Ludwig Levin Jacobson identified Jacobsonโs organ in 1813.
Jacobsonโs organ detects nearly seemingly scentless things like pheromones. If pheromones are detected, the organ sends the information to what some experts call a โsecondary olfactory organโ in the brain to trigger the mating instinct. Australian scholar Michael Stoddard published a paper in Nature (2000) that called the organ a โsixth sense.โ
Dogโs Amazing Ability to Detect a Scent
It is possible that a dog who is panting more out of interest or excitement rather than fatigue may be using that open-mouth, tongue-out posture to bring more air past Jacobsonโs organ to help identify a smell. Experts continue to be amazed at what dogs can find by smell. A dogโs ability to detect a scent is said to be 10,000 to 100,000 times that of a human, according to a 2018 research study published in Frontiers in Veterinary Science.
Recent studies show that dogs can detect not only specific scents of drugs or explosives, but dogs can also note changes in emotions and human cell metabolism during various illnesses, including COVID-19 infection. And, of course, dogs are critical in the search for a missing person.
Itโs interesting to note that scent work is a fast-growing sport. Both humans and dogs appear to be enjoying doing nose work (or scent work) competitions. Noting and tracking a scent is like reading a newspaper to dogsโitโs information. That love of smelling things is one of the many reasons experts encourage us to allow our dogs to sniff about when weโre on walks.
