Everybody who has domestic cat sooner or later starts wondering why does his pet behavior depends on different situations - in the dusk and darkness, near running car and in the garden. There're several reasons, but the main is other then ours abilities to percept surround reference points. One should always remember, that cats percept the world in some other way then we do. They hear, see and smell in another way, and, hence, differently orient themselves in environment. Their behavior depends on this, sometimes incomprehensible for us. This is just because different objects are important for them. Human criteria for them are as strange and cat's criteria for us.
Though our friends have such expressive eyes and big mobile ears, the main sense organ for a cat is smell, not so conspicuous at first sight. This is due to the fact that the world of cat is a world of odors, scents. This is not a big deal for a blind and deaf cat to live in a human world. It is able to lead a full live even at forest. But not a cat, which has no smell. It is just unable to survive.
Environment is full of different odors: here are the smells of its' kittens, and loving master, and members of the family, and its' enemies - dogs. And of cause, remember odors of kitchen. Cat has its own estimates. Something that is unpleasant for us, for example, a smell fermented beef or chicken bowels - lungs and liver, or fish remains, may attract a ca, especially if it is hungry. On the contrary, its' own bowl, washed with soap till clean frightens a cat off because saves the odor of detergents that we can't feel but that actively affect a cat. A cat masks paths and pavements that are of her own with its' odor, masks forbidden territory, that it prefers to escape, and at last, areas that are allowed to visit for several cats. By means of odors a male gets an information about another male which have pretensions on its' own territory, or about a female ready to heat. Smell gives cats lots of information about food cooked at kitchen, or about pray which still walks or creeps and which is to be caught.
In spite of outwardly unpretentious size of cat nose the organ of smell inside its' head occupies pretty much space. Nostrils lengthen as nasal ducts and cavities, with perceptive cells in back sections that on the whole form the olfactory area of nose. Lattice "shells" situated here form a complex nasal labyrinth through which air filled with odors comes to perceptive cells. During the process of smelling cat actively draws the air in and provide a direct connect between perceptive cells and molecules of odorous substance. Perceptive cells are a region of brain bulged out on a nose surface. The cells are directly connected to olfactory centers. The connection occurs through internal endings of perceptive cells that are united in thin threads of fibers and penetrate through holes in lattice bones. Here, in brain cavity the olfactory lobe receives them and sends a thick bunch - olfactory tract - "convolutions of hippocampus" - to different sections of brain. The olfactory centers of cat include up to 67 millions of cells, 1,5 millions more then in human. A part of olfactory region of nose is stands apart as a Jacobson organ/ sometimes called voter-nasal by its' location near the base of mouth. It consists of two symmetrical tubes that lengthen along the palate into Steenson ducts. Small apertures behind front teeth connect this organ with environment. A cat draws the air in the apertures, at that it stops rooted to the ground, opens its mouth and draws the lips in, wrinkling the skin on its' head in a kind of grimace (Flemen's smile).
Functions of Jacobson organ are still unclear. At least three main hypotheses exist. According to one of them, the organ percepts the smell of food, coming in mouth as if getting information additional to that received by smell. Supporters consider a cat possess a mouth sense of smell.
The second hypothesis says that a cat analyses air flows in the atmosphere that reflect small alterations of chemical composition as a result of considerable events - eruption, earthquake, approach of forest fire and so on. Supporters of this hypothesis call this organ a sixth sense that helps cats predict more than usual accidents.
The third hypothesis features Jacobson organ the role of informer specialized on perception of odors relative to sexual sphere - pheromones. Of cause, Jacobson organ would be very attractive as an organ that percepts delicate odors beyond human perception but still there's not enough reasons for this assumption.
The extent of ability to smell is comparable to size of olfactory organs. Animals called microsmatics this ability is more poor and their olfactory organs are small (Primates, seals, whales). In return, in rodents, ungulates and carnivores the ability to smell is of extreme sensibility, and these are called macrosmatics. A dog is able to follow in the pray tracks left several hours ago. A mouse by the smell is able to find seeds under the ground, and a badger - larvae of cockchafer 10-15 cm under. Cat sense of smell is weaker then dog but much stronger then human. However sometimes among cats individuals with exclusive smell occur (in the same way as among humans whose profession deals with odor determination - tasters of wine, perfume, etc.). Smell is associated with taste. Virtually they carry out similar tasks, analyzing chemical substances, at the distance (smell), or at the direct contact (taste). Taste and smell supplement each other in the case of cats, after all a cat likes food that at its' angle smells nice.
Where are senses of taste situated? If one looks at a cat tongue then he will see about 1500 of papillary projections on its' surface. There are gustatory bulbs, or gustatory knobs inside them. Bulbs are look like bottles with a small hole (gustatory pore) that opens on the surface of tongue. Nerve fibers enter bulbs and terminate there loosely. Each bulb consists of external - supporting cells - and internal - gustatory cells. Gustatory fibers from different bulbs are a part of singular bunch of medulla and terminate in the area of its terminal nucleus. Gustatory fibers from this nucleus go into nuclei of middle brain and then into cerebral hemispheres were they terminate in the neighborhood of olfactory centers, confirming once again the association between taste and smell.
Substances discerned by sense of taste are grouped in four categories: sour, salty, bitter and sweet. At the same time different predators have different ability to differ make them out. Cats, for instance, discern bitter well, and sweet much worse. However because usually smells are present, it is not that easy to determine how does something is discerned. Anyway one should always take this into account. For example a cat accidentally get into garage may leak antifreeze being attracted by its' smell and suffer irreversible kidney lesion. The fact that antifreeze has a sweet taste is not so important for a cat because of poor ability to percept sweet. Don't give your cat sweets because it causes hard diseases of teeth and gums. Though a cat doesn't like sweet, but at certain circumstances it may crave for it, which will be very difficult to get rid of.
Sometimes it's impossible to explain their craving to some substances and plants. For example, catnip contains nepethalactone attracting all Felidae and from a half to two thirds of all domestic cats. Cats smell at the plant, leak and chew it. Then they roll on the floor, rub themselves on leaves or stare at them. Well-known valerian influences much cat behavior. Though the mechanism this substances act is unknown, they surmise that it is related to drugs. However others suppose these substances to include some components of pheromone effect.
At all times with the use of smells unpleasant for cats people try to control their behavior scaring them away from places where they are unwanted.
Roman philosopher Plinius wrote that cats were scared away from dovecots by planting cultivated rue around it. Many substances with bad smell, citronella, for instance, are also good as a "catscarer". Anyway this method is worth attention because may help many cat-fanciers or their neighbors.
Valeriy ILYICHEV, Doctor of Biology, professor
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).