The question in the title is a reference to the Jacobson’s organ a.k.a. the vomeronasal organ. The question in the title is slightly inaccurate as the vomeronasal organ is a separate to the usual nasal cavities.
All cats and some other animals (snakes and many mammals) have this and it is located inside the nasal cavity and opens into the roof of the mouth behind the upper incisors. It is a secondary olfactory system. It is supersensitive and allows cats to detect specific chemicals. This very special organ can detect undetectable odours.
Jacobson’s organ is comprised of two small fluid-filled sacs and is connected to the mouth and nasal cavities through the nasopalatine canal. It contains receptor cells which connect to the nerves leading to the amygdala region of the hypothalamus, the brain region associated with sexual, feeding and social behaviours.
Note: This is a video from another website. Sometimes they are deleted at source which stops them working on this site. If that has happened, I apologise but I have no control over it.
It is thought to be involved in feline courtship and sexual behaviour and to help the snow leopard and another species of cat to identify and recognise other cats. When the organ is used the snow leopard employs the ‘Flehmen response’. The cat sucks in the air to drive it onto the nasopalatine canals.
The photograph on this page shows this happening. In order to suck in the air, the head can be raised slightly and the lips drawn back while the mouth is partially open and the nose wrinkled. It is also called gaping. In domestic cats it is most often observed in unsterilised males but both male and female cats use it.
In response to the question, “Why do snow leopards have enlarged nasal cavities?” the answer is to pick up almost imperceptible odours in the air which inform snow leopards about the presence of other snow leopards through scent marking on its home range and if they are males the presence of females for mating purposes.
Here is a tiger gaping:
SOME MORE ON THE SNOW LEOPARD: