Why cat urine smells so bad: Scientists reveal what causes the unique stench - and what to do about it

No matter how cute they might be, there is no denying that cats' urine really stinks - particularly when sprayed.

Scientists have never been exactly sure why sprayed urine smells worse than what's left in the litter tray, but now some believe they have found the answer. 

Researchers from Iwate University, Japan discovered that cats' urine contains high levels of a protein called cauxin. 

They suggest that this chemical increases the urines 'wettability', meaning it sticks to surfaces and dries quickly - releasing lots of smelly volatile compounds.

If you're sick of your house stinking, thankfully scientists say there's a simple way to eliminate cat odour.

Scientists have revealed that cats' urine smells worse when it is sprayed due to a protein called cauxin which makes the urine stick to surfaces  

Cats, like many other animals, communicate with each other through scent and will spray their urine on vertical surfaces like walls and trees.

But for the humans that have to deal with their cat's scent messages, the results are an extremely pungent odour.

Until recently, some scientists thought that cats' urine smelled worse when it was sprayed because it contained additional chemicals from anal sac secretions.

To put this theory to the test, scientists took samples of sprayed urine, normal urine, and urine collected directly from cats' bladders using urethral catheters.

When these samples were chemically analysed the urine from each cat had a high degree of similarity, regardless of where they came from.

The behaviour of cats who smelled the samples also suggests that samples from one animal smell the same whether they are sprayed or not. 

This indicates that sprayed urine and urine in the litter tray are actually the same at the chemical level, even though they smell very different to a human observer. 

However, during their testing, the researchers noticed that cat urine samples 'easily adhered' to the inside of the plastic syringes used to transport them.

Reiko Uenoyama, the paper's first author says: 'This observation prompted us to explore the underlying mechanisms.'

Cat spray smells bad because proteins in the urine let it stick to surfaces even outside. That means you need to clean it quickly before the urine dries and the smell becomes more intense (file photo)

It was already known that cat urine contains high levels of cauxin, which contributes to the distinctive 'catty' smell of urine.

However, it was not known what effect this had on how urine smells when it is sprayed. 

Ms Uenoyama says: 'Generally, the wettability of a liquid on solid surface increases as the surface tension decreases. 

'Based on this knowledge, we hypothesized that the high protein concentration in cat urine might reduce the surface tension of cat urine, enhancing the emission of urinary volatile compounds from the large vertical surface area that was spread over the urine.'

By comparing cat urine against samples from which the protein had been removed, the researchers found that urine with proteins had much lower surface tension and showed significantly greater adhesion to vertical glass plates during testing.

In a miniature garden built by the researchers, observers were easily able to smell when a block sprayed with tomcat urine was introduced.

However, when that same urine sample was poured onto sandy soil and then covered, no smell could be detected.

Professor Miyazaki, who first discovered that cat urine contains cauxin, says: 'Liquid droplets of sprayed urine can easily dry on the surface of the block, resulting in greater emissions of volatile chemicals from the scent mark rapidly as compared to from normal urine.'

Previous research has shown that the odour of cat urine is produced as cauxin and a second compound called felinine.

To remove cat odour researchers say that owners could add a cauxin inhibitor to their cats food, although they caution this would be difficult.

As an easier alternative, scientists recommend treating the area with compounds containing metal ions like gold, silver and copper.

These ions bond with the volatile chemicals which produce the smell, eliminating the odour at its source.  

HOW WELL DO YOU KNOW YOUR CAT? THE 13 SECRET SIGNALS FELINES GIVE THEIR OWNERS

Cats are often branded aloof and solitary creatures who spend their days plotting their human owner's demise, but such characterisations could not be further from the truth.

In fact, our feline friends constantly communicate their feelings of affection to us, whether it be through their whiskers, tail, face or body language.

In her eye-opening new book Kitty Language: An Illustrated Guide to Understanding Your Cat, author Lili Chin - with the help of animal behaviourists - explains how to interpret your pet's movements.

Below are some of the most common behaviours and what they could signal.

Our feline friends constantly communicate their feelings of affection to us, whether it be through their whiskers, tail, face or body language