Tomcats advertise their fitness and prowess through the smell of their sprayed urine

Female cats can be choosy in selecting a male and thereby procreate. She uses her courtship to select her favoured male or males. Males can impress females through the pungency of their urine. They are advertising their fitness and ability to procreate and create fit families through the smell of their urine. It’s remarkable that female cats can read the scent of urine in this way.

Cat spraying
Cat spraying. The urine contains information about the tomcats hunting skills. Photo in public domain.
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Tomcat urine contains vital information for a cat although it smells very strong and rather unpleasant to people. The tomcat makes sure that the urine is exposed to as many other cats as possible by projecting it horizontally, while on tiptoes, to a vertical object. The powerful smell is much stronger than that of females or neutered males. The odour is caused by a mixture of a sulphur-containing molecules called thiols. These are similar to the molecules which give garlic its strong smell. These molecules don’t appear in the urine until they’ve been voided from the cat and come into contact with the air. The molecules are stored in the bladder in an odourless form as an amino acid called felinine which is generated in the bladder by a protein called cauxin.

Felinine is made from two amino acids, cysteine and methionine. They both contain the sulphur atom which creates the pungent odour. Cats cannot make these amino acids. They have to come from high-quality protein in their diets.

The ‘success’ of a male cat is judged by their hunting prowess. The more successful male hunter will have a better diet. From that better diet they are able to obtain high-quality protein which in turn includes the two amino acids referred to. Therefore, they are able to produce a more pungent odour from the urine when it is sprayed.

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In this way the more successful male cat is able to signal to a female his hunting prowess and therefore his fitness to be a good father. This is because he will produce offspring with the same qualities who will more likely survive. Therefore, the female gets what she wants which to produce healthy offspring who survive and the father is able to build a family which can carry his genetic profile forward.

The urine spraying also contains information about the identity of the tomcat who produced it. This allows females to identify the best hunter and the best potential father. It seems that this method of identification through the smell of urine is work in progress by the scientists. Dr. Bradshaw says that it is probably signalled through something other than the pungent sulphur compounds.

The smell of cat urine is a badge of quality of the individual who produced it. A male cat who is incompetent or a poor hunter and perhaps sickly as a result will be unable to obtain enough food to make his urine pungent.

It is believed that the evolution of this process is driven by the females when selecting males. My mind turns to another topic but a linked one. Male domestic cats, even those who have been neutered, probably seek out the highest quality foods they can get as a natural instinct. Perhaps this may be why they might turn up their noses at low quality, low protein food when offered it by their caregiver. That’s just a thought. Perhaps a vague thought but if a male cat is picky about the food that he eats it may be linked to the reasons stated above. Although I suspect neutering might remove this instinctive demand.

P.S. A cat’s stool also contains information about the cat. Defecation is also used to mark territory. It is believed that chemicals in the product produced by the anal sacs are injected into the stool as it is voided adding the scent signature. Cat anal sac secretions contain 52 bacteria produced compounds.

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