Mystery Over Why Cat Spray Smells So Bad Finally Solved

Urine sprayed by cats has always had a much stronger odor than normal urine, and now researchers know why.

Cats communicate with others by producing various scents. Spraying is one such behavior. They will often do this on walls or pieces of furniture.

Cats usually spray to mark their territory. All cats are capable of doing this, but it is more common in unneutered male cats. The smell can be seriously unpleasant.

Although the liquid sprayed is just urine, it smells more pungent than the normal stuff in the litter box. The exact reason for this remained unclear. But now, Japanese researchers found that this is likely because the sprayed urine comes straight from a cat’s bladder, meaning it does not contain certain chemicals.

To reach their findings, the researchers compared chemical profiles of sprayed urine, normal urine, and urine that came straight from the bladder. They then conducted behavioral analysis, to see how cats reacted to these different scents.

An analysis of all three found that cats perceived sprayed urine and bladder urine as having very similar odors.

The findings suggested that urine that is sprayed originated from bladder urine, without additional chemicals from secretory glands, as normal urine contains.

Having found that a cat’s sprayed urine is the same as its regular counterpart, the team decided to look closer at the liquid’s makeup to see if that yielded any clues. They ended up zeroing in on a specific protein called cauxin, which is found in high concentrations in cat urine. They found that cauxin changes how the urine behaves in different situations.

“Generally, the wettability of a liquid on solid surface increases as the surface tension decreases,” the paper’s first author, Reiko Uenoyama, said in a statement.

“Based on this knowledge, we hypothesized that the high protein concentration in cat urine might reduce the surface tension of cat urine,” Uenoyama said.

This, Uenoyama explained, would mean that when a cat sprays over a large vertical surface, like a wall, it releases more pungent volatile compounds into the air.

As an additional measure for research, the scientists constructed an artificial garden in order to distinguish how the odors would smell in this natural environment.

“The difference in environmental odors between the two gardens, despite using the same urine sample, can be explained by most of the urinary volatile chemicals being trapped in the porous structure of the sandy soil,” Masao Miyazaki, a leader of the research project, concluded in a statement.

“This phenomenon did not occur in the urine adhering to the surface of the block. Additionally, 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.”

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