Tom-cats mark their territories by squirting a powerful jet of urine backwards on to vertical features of their environment. They aim at walls, bushes, tree-stumps, fence-posts or any landmark of a permanent kind. They are particularly attracted to places where they or other cats have sprayed in the past, adding their new odour to the traces of the old ones already clinging there.
The urine of tom-cats is notoriously strongly scented, so much so that even the inefficient human nostrils can detect it all too clearly. To the human nose it has a particularly unpleasant stench and many people are driven to having toms neutered in attempts to damp down this activity. Other cat odours are almost undetectable by humans. The glands on the head, for example, which are rubbed against objects to deposit another form of feline scent-mark, produce an odour that is of great significance to cats but goes completely unnoticed by the animals’ human owners.
Some authorities have claimed that the squirted urine acts as a threat signal to rival cats. Hard evidence is lacking, however, and many hours of patient field-observation have never revealed any reactions to support this view. If the odour left on the landmarks was truly threatening to other cats, it should intimidate them when they sniff it. They should recoil in fear and panic and slink away. Their response is just the opposite. Instead of withdrawing, they are positively attracted to the scent-marks and sniff at them with great interest.
If they are not threatening, what signals do they carry? The answer is that they function rather as newspapers do for us. Each morning we read our papers and keep up to date with what is going on n the human world. Cats wander around their territories and, by sniffing at the scent-marks, can learn all the news about the news about comings of the feline population. They can check how long it has been since their own last visit (by the degree of weakening of their scent-spray) and they can read the odour-signs of who else has passed by and sprayed, and how long ago. Each spray also carries with it considerable information about the emotional state and the individual identity of the sprayer. When a cat decides to have another spray itself, it is the feline equivalent of writing a letter to The Times, publishing a poem, and leaving a calling card, all rolled into one jet of urine.
It might be urged that the concept of scent-signalling is far-fetched and that urine-spraying by cats is simply their method of getting rid of waste products from the body and that it has no other significance whatsoever. If a cat has a full bladder it will spray; if it has an empty bladder it will not spray. The facts contradict this. Careful observation shows that cats perform regular spraying actions in a set routine, regardless of the state of their bladder. If it happens to be full, then each squirt is large. If it i nearly empty, then the urine is rationed out. The number of squirts and the territorial areas which are scent-marked remain the same, no matter how much or how little liquid the cat has drunk. Indeed, if the cat has completely run out of urine, it can be seen continuing its scent-marking routine, laboriously visiting each scent-post, turning it back on it, straining and quivering its tail, and then walking away. The act of spraying has its own separate motivation of its importance in feline social life.
Although it is not generally realized, females and neutered cats of both sexes do spray jets of urine, like tom-cats. The difference is that their actions are less frequent and their scent far less pungent, o that we barely notice it.