This is a classic example of a domestic cat using her vomeronasal organ (‘VNO’ also called the Jacobson’s organ) to smell and analyse the odours coming off her owner’s foot. She also licks the foot for taste. The face that the cat pulls gives us the impression that she is unimpressed but in fact she is simply using her super efficient and sensitive vomeronasal organ.
This organ is a second olfactory apparatus for the cat. It is an organ that humans don’t possess and it’s function is between smell and taste.
The way it works is fascinating and complex. The organ contains 30 different types of receptor which is a lot more than the dog’s nine. It can detect a wide range of smells and analyse them. The receptors are connected to a dedicated part of the brain called the ‘accessory olfactory bulb’. They are quite separate from the receptors in the nose.
A couple of incredibly thin tubes (one hundred of an inch wide) run from the roof of the mouth behind the upper incisors to the nostrils. A sac is connected to each tube about halfway up. This is the VNO and it is filled with chemical receptors. The VNO is full of fluid.
Because this smell detector uses fluids to detect smells the odours have to be carried to it inside a fluid, namely the cat’s saliva.
As the tubes are so narrow the fluid has to be ‘pumped up’ to the VNO and out of it by dedicated muscles. Control over these muscles provides the cat with the means to decide when to use the VNO.
When the cat does use the VNO she pulls a face. You may have seen it in videos and the video on this page is a rather delicate domestic cat version of it. The snow leopard’s facial expression and that of the big cats is far more pronounced.
The cat performs a gaping motion with the mouth. It is believed that when the mouth is open like this the cat’s tongue is ‘squeezing saliva up into the canals, from where the pumping mechanism delivers it to the VNO. This is the Flehmen Response.
Cats perform it exclusively in social situations. So they use it to detect the smell of cats and as can be seen in the video the smell of their human guardian who they regard, in my view, as a surrogate mother cat of impressive size.