As you might know, cats have an acute sense of smell. Smell is very important to us in many ways as it is part of our language, but can we smell unusual occurrences, such as earthquakes, or volcanic eruption? Some humans believe this is so.
Our very good sense of smell is due in part to our well-developed olfactory bulb and also to a large surface of olfactory mucosa. Our olfactory mucosa is about 5.8 cm in area, which is about twice that of humans and only 1.7-fold less than the average dog. When we breath in, the air passes through this membrane and the millions of cells send a response signal to the brain via the olfactory nerve.
We are very sensitive to pheromones, which we use to communicate through urine spraying and marking with scent glands near our faces and in our feet. This is why we rub up against our humans so much, as well as the things in our territories that we value; we are marking them as ours. (Although some cats, like tabby brofur never pay attention to these messages.)
Now, we also have a special scent organ in the roof of their mouths called the vomeronasal (or Jacobson's) organ. When you wrinkle your muzzle, lower your chin, and let your tongue hang a bit, it is because you are opening the passage to the vomeronasal. The humans call this activity gaping, "sneering", "snake mouth", or "Flemming". Dogs, horse and big cats are among the other animals that do this same movement because they have the same vomeronasal ducts in their mouths.
There our several ways in which use the vomeronasal ducts. The first is to taste smells. This helps us identify food and whether or not is good to eat. Needless to say, this is very important for our hunting as well. Humans, of course, have a completely different way of identifying which foods we will eat, which I call the Friskie's method:
The second is to help perceive sexual odors - pheromones. During mating, smell is the most important of all of our senses, as it helps us recognize and identify the sexual readiness of our intended mate. Neutered house cats do no use this option so often, but many times I will have suiters come and sing at my window when they are looking for a mate, hoping for a better whiff of me.
If you were neutered late in life, you might still exhibit some of activities related to sexual maturity in cats, and will use your vomeronasal ducts to search for pheromones.
The third use is to sense atmospheric information - like coming rain showers - or yes - volcanic eruptions.
Now, because of our very sensitive noses, most cats also respond strongly to plants that contain nepetalactone, especially catnip. We can detect that substance at less than one part per billion.
This response is also produced by other plants, such as Oleander, stocks, valerian, pinks and sorrell, and may be caused by the smell of these plants mimicking a pheromone and stimulating our social or sexual behaviors.
Not all cats have this response, and it is not present in young kittens at all.
We do NOT like the smell of vinegar, which humans have discovered. They have found that the sprinkling of vinegar will make us stay away certain places, or will stop us form urinating in inappropriate places (although it will not change the reason we are doing it in the first place. If you are urinating in an inappropriate place you should still see a vet immediately! You may have a urinary blockage which is life threatening condition!)
Other smells, such as marjoram or oregano can make us aggressive.
A cat's nose leather may be either black or pink, depending on genetics and your basic coloring. It is a pretty tough surface, probably from our propensity to stick our noses into places they shouldn't be.
One caution should be kept in mind, however, for the conscientious caregiver. White or light-colored cats are susceptible to a squamous cancer of the nose and ears, especially when exposed to the sun over long periods of time. Light colored cats should be kept indoors, or should use a veterinarian-approved sunscreen on delicate nose and ear tips if going out in the sun for long periods of time.
Smell is our way of exploring our world. We are able to detect odors that humans can't. Unfortunately, just as with some humans, our sense of smell deteriorates with age. Infection and injuries caused through fighting can also affect our sense of smell. For a cat, the loss of a sense of smell creates a huge handicap. It makes it very hard to catch prey, communicate with other cats, and can leave us open to being injured in a fight if we wander into the territory of another cat.
If you find you are having problems with your sense of smell, it may be best to limit your time outside and stay close to home, where you will be protected.