Female cats can be choosy when selecting a father for their kittens. Tomcats (unneutered male cats) advertise their success before meeting the female. Dr Bradshaw believes that they probably do this through the pungent smell of their urine. It contains vital information for a female cat. We know about cat spraying. The tomcat will backup towards a prominent object such as a gatepost or wall, raise his tail, stand on the tips of his hind toes and spray urine onto the object as high up as possible.
The powerful smell of a tomcat’s urine is caused by a mixture of sulphur-containing molecules called thiols. These are similar to the molecules that give garlic its characteristic smell. Interestingly, they don’t appear in the urine until it has been voided i.e. until it comes into contact with the air. In the bladder the molecules are stored in an odourless form as an amino acid. It was first discovered in cats and given the name “felinine” which is made from two amino acids, cysteine and methionine. Both these amino acids contain the sulfur atom necessary for the creation of the pungent odour.
Importantly, cats cannot make these amino acids by themselves through their own metabolism. The amount of felinine that a tomcat can make is determined by the amount of high-quality protein in his diet. In turn, with respect to feral cats, this is determined by how successful the tomcat is as a hunter. Therefore there is a connection between the pungency of his urine and his prowess as a hunter and therefore good at obtaining food. The female cat will recognise this connection and of course she is looking for a male cat who is good at obtaining food for her kittens to be.
Scientists are working out how female cats can identify a urine mark with the tomcat that created it. There must be some marker other than the pungent sulphur compounds which gives them the clue. For a tomcat the odour of his urine is “a badge of honour”. A sick tomcat will be unable to obtain enough food to make his urine pungent. Dr Bradshaw states that the evolution of this signal in urine was probably driven by females selecting males on how smelly their urine is. Males unable to make felinine would not be favoured by females. For non-feral cats who are unneutered being fed high quality commercial food should make him more attractive to females.
Source: Dr Bradshaw’s Cat Sense (digital download on Kindle) – highly recommended.
